Dr. Fatima Adhaim: Mixed-Matrix Membranes Formed from Different Morphologies of Zeolitic Imidazolate Frameworks for Gas Separation

Wednesday, Jun 30, 2021

Webinar

Dr. Fatima Adhaim: Mixed-Matrix Membranes Formed from Different Morphologies of Zeolitic Imidazolate Frameworks for Gas Separation

In this webinar, Dr. Adhaim will highlight the research conducted during her IBK fellowship, which focuses on the simple and straightforward method she helped develop to rapidly form ZIF-8 with branched architectures at ambient conditions in a short amount of time. The branched ZIFs can be added to a polyimide matrix and formed into stable and well-dispersed MOF networks to form MMMs. Unlike traditional ZIFs particles, which are roughly spherical, branch ZIFs form anisotropic percolation networks at low loadings without the need for alignment. Such morphological features present opportunities to study known and new MOFs with these unique structural features. In addition, these branched ZIFs have high external surface areas, which can favorably interact with polymers. These features enable the stabilization of the polymer structure while simultaneously inhibiting plasticization. Her research expanded the materials scope and characterization efforts into other MOFs that contain the same organic ligand.

Her research also studied the synthetic mechanism of branch ZIFs by exploring different experimental conditions. Her results reveal that various morphologies like rhombic dodecahedron, filled sphere, mesoporous aggregation, and hollow sphere could be obtained via manipulating the synthetic parameters.

Biography

Fatima Adhiam was born and raised in Saudi Arabia. She began her academic career in chemistry at Imam Abdurrahman Bin Faisal University, where she studied organic and inorganic chemistry. After graduation, Fatima joined Saudi Aramco to work as a senior laboratory scientist in the Research and Development Center (R&DC). While at Aramco, she led different research activities in the oil and gas fields, which supported upstream and downstream operations. She focused on utilizing the advanced properties of the XRD and WDXRF instruments to be used in multi-function applications. She was also working on the synthesis and characterization of refractory materials using Saudi Aramco by-products.

In 2017, Fatima obtained her Ph.D. in Chemistry Science from King Abdullah University of Science and Technology, KAUST. During her research, she worked on the synthesis and characterization of quaternary metal chalcogenide aerogels for gas separation and volatile hydrocarbon adsorption.

In 2020, Fatima joined the Smith lab, Massachusetts Institute of Technology (MIT), as a postdoc fellow. Her current research interests include developing and characterization of zeolitic imidazolate frameworks (ZIFs) for gas separation.

In her spare time, Fatima enjoys hiking, shopping, cooking, and playing with kids.



Webinar Transcript:

DOROTHY HANNA: Good afternoon, everyone. Thank you for being here. My name is Dorothy Hanna and I am the program administrator for the KACST MIT Ibn Khaldun fellowship for Saudi Arabian women. Welcome to today's IBK webinar presented by Dr. Fatima Adhaim based on her research at MIT this year, which is titled mixed-matrix membranes formed from different morphologies of zeolytic imidazolate frameworks for gas separation.

Please post your questions in the chat as we go along and we will answer them at the end. And first, our program director, Professor Kamal Youcef-Toumi will introduce Dr Fatima's advisor, Professor Zach.

KAMAL YOUCEF-TOUMI: Great. Yes, thank you. Thank you, Dorothy, and thank you for everyone for joining us this afternoon. This is part of Ibn Khaldun fellowship seminar series. And I would like to thank Professor Zachary Smith for working with Fatima and supervising her activities in his department.

So professor Smith is a professor at the Department of Chemical Engineering at MIT. His research focuses on the molecular level design and synthesis and also the characterizations of polymers and inorganic materials. So some of the applications that he has been focusing on with his team is in the membrane and absorption-based separations.

And so professor Smith, because of all of his contributions, he has been recognized with the several awards. I'm just going to mention a couple of them here. One is the Early Career Award from the Department of Energy, the DOE, and also the Young Investigator Award from ONR or the Office of Naval Research. And then in addition to that, he was recognized by the American Institute of Chemical Engineers in the program of the 35 under 35 award.

He has published extensively in these areas. And he also co-founded the Flux Technology and Osmosis Incorporated Company. So Professor Smith has earned his degrees in Chemical Engineering from Penn State University. And also his PhD from Texas, Austin. And he has done also a post-doc in the past of the University of California, Berkeley.

So thanks again, Zach, for all your help not only with Fatima but also with our Ibn Khaldun program. And I'll hand it over to you now, maybe to have an introduction of Fatima before her presentation. Thank you.

ZACH SMITH: All right. Well, thank you all for the introduction. I'm really happy to introduce Fatima as well. I'm excited for the presentation today.

Fatima comes from of course, Saudi Arabia as part of her fellowship. And she's trained in chemistry, actually completing her chemistry degree back in 2004 at the Girls College in Dammam. She went on to work at Saudi Aramco while also pursuing degrees at KAUST and this includes her work with her MS and also her PhD. And where Fatima really stands out is working in the realm of inorganic materials, crystallography, characterization type work. And so when she came to my lab at MIT, I, of course, put her on a really hard project involved inorganic chemistry and characterization.

She came around 2019, 2020 so just in time for the pandemic actually, but dove right into the lab making things and adjusted very well. During the time where we were away from campus and then eventually getting back to shift hours, and just recently back to what is a semi-normal routine and actually having in-person meetings. So she's been here that entire time and has done a wonderful job working with ZIF materials that she'll talk about today.

Also came here with her family, who I had a chance to meet as well just recently. So I had to balance lots of things during this time but really appreciated all the work that Fatima did and really excited to see this final presentation on her work. So Fatima, when you're ready, you can go ahead and get started. We're looking forward to your presentation.

FATIMA ADHAIM: Thank you, Professor Zach for the nice introduction and the kind words. Just a moment. So good afternoon, everyone. Today, I'm going to explain and show you some information related to my work at MIT entitled mixed-matrix membrane formed from different morphologies of zeolytic imidazolate frameworks for gas separation.

During the presentation, I'm going to give you a brief introduction. Then I'm going to discuss the synthetic factor controlling particle size and morphologies of ZIF-8. After that, I'm going to talk about the structural effects of MOF's on gas permeation via mixed-matrix membrane. And finally, I'm going to conclude the presentation with a conclusion and acknowledgments.

So let's move on to the first part of the presentation, which is the introduction. In fact, the natural gas consumption steadily increases every year as do CO2 emission. In 2016, the total US energy consumption was around 98 quads out of four different sectors.

Chemical industries consumed around 32% of this energy. However, half of this energy is consumed by the thermal separation like distillation, drying, and evaporation. However, the most energy is consumed by the distillation process. Thus, it has been confirmed that the membrane material would save around 90% of this energy compared to the distillation process. So implementing more energy-efficient separation method would reduce the greenhouse gas emission and save a lot of money.

Membrane material can be used as an alternative conventional separation method, not only because membrane material consumes lower energy compared to the others. The membrane material could increase the separation efficiency up to 90%. Comparing to the solvent system and membrane system would require smaller spaces. Furthermore, membrane material can separate both organic and inorganic substances. Membrane materials are clean technology with operational ease as well.

However, the most of the commercial membranes that are available in the market are made by the polymers. And the polymeric membrane are associated with some drawbacks like the upper-bound trade-off, and the permeability, and the selectivity. Furthermore, there is an issue or challenge in these materials in terms of the stability against the plasticization. I mean by that, at higher pressure of this material would start to swirl the CO2 on the hydrocarbons and in this case, it would result in higher permeability. And the higher permeability of the polymeric membrane are usually associated with a significant reduction and the selectivity.

On the other hand, a pure MOF membranes can surpass this upper-bound. However, this material becomes so fragile if we scale of this material into industrial scale which would result in poor film formation. In a pure sense, mixing these two components and the advantages of the polymer and MOF components which result in a mixed-matrix membrane with good processibility, high performance, resistance to the plasticization. However, there is a wide range of MOF material and the gas separation and gas transport of mixed-matrix membrane depend on the type of MOF particles in it.

So I was working on zeolytic imidazolate framework. This material are a subclass of metal organic framework. These materials enherited the tunable porosity, structural flexibilities, and the functionalization of the internal surface of MOF material as well as they inherited the thermal, mechanical, and chemical stability of zeolite material.

These materials possess interesting properties along to their structure. So the basic repeated unit of zeolite material silicon oxygen silicon that's represented in this material with the transition metal in a place of silicone atom and imidazole in a place of deprotonated oxygen atom. Also the angle that's made by the transition metal imidazole transition metal similar to that and zeolite material.

ZIF-8 material was the zeolite structure with the small aperture size of 0.34 nanometer and large cage of 1.16 nanometer. However, the gas transportation of ZIF material depends on the particle size and morphologies. Therefore, I was working on this material with an ultimate goal of being able to systematically tune the size and morphologies of ZIF-8 and then study the gas transport.

So in order to achieve the first part of my goal, I have to answer main research questions, like what is the effect of the modulator addition? What is the influence of the reaction time and temperature, the influence of Zinc sources and molar ratio? And what is the influence of solvent that is used in the reaction? And the most important question is that, would it be possible to generalize our method into other ZIFs like ZIF-67?

So in order to answer all of these questions, we need to know that ZIF-8 material can be constructed from any zinc precursors, [INAUDIBLE] methylimidazole. Methylimidazole can work as a stabilizer in it's natural form and as linker in its deprotonated form. Furthermore, the low pH can lead to stabilize the linker in its natural form.

Looking into this [INAUDIBLE] region, we can see that as ZIF material is formed, nitric acid is also formed. And this would lead to a decrease at the edge of the solution, which would limit the rate of the phase transformation. So the main reason to add the modulator in this case is to enhance the reaction by deproteination of the ligand and denucleation of the material so the deproteinated modulator would maintain the proper protonation state. Furthermore, it would naturalize the acidic the product.

However, in order to study the synthetic factor controlling the particle size and morphologies of ZIF A, we need to answer all of these questions and investigate all of these reaction conditions. However, due to the time limit today, I'm going to show you only the effect of the modulator addition, the influence of the reaction time, the influence of zinc sources, and would it be possible to generalize this method into other ZIFs. So, in order to start with the effect of the modulator, I've used 10 amine-based modulator and different zinc sources. But today, I'm going to show you the results related to zinc nitrate hexahydrate.

The reaction was held for around 60 minutes at room temperature using methanol as the solvent. So TEM results shows that, in case of the absence of the modulator, ZIF material says large particle size rhombic dodecahedral shape and sharp edges and corners. However, in case of the addition of pyridine as a modulator, with low PKA volume conjugated as such, we can see that there is a slight reduction and turn of the particle size. And also, this particle was just irregular morphology. And we can see there is no sharp edges or corner in this case.

Additon of amylene, which was a slightly higher of PKA volume, we can see that the particle size is getting-- are getting smaller, and they are still attaching into each other. However, the addition of trimethylamine, with higher PKA volume, we got the first branch material. And as you can see here, the particle is much smaller than the others. And the morphology in this case, the particle-like nano strand attaching to each other in a random direction for the smaller particle size can be obtained from the higher PKA in a butylamine. And in this case, we can see that the particle size is much smaller.

And this behavior actually can be attributed to that. The addition of the modulator would enhance the nucleation of the ligand and, hence, rapidly anucleate the ZIF-8 material. And this nucleation of ZIF-8 material-- I mean, the particles out of this rapid reaction would grow into smaller particle size because there is no time for this particle to grow up due to the rapid reaction and the super saturation solution.

So as these reaction have been repeated several times using eight different ZIF sources and different enamine-based modulator. And we usually get the same trend, we can confirm that deprotonation by the ligand-- I mean, the deprotonation of the ligand by the modulator would affect the morphology of ZIF-8. Furthermore, demodulator with higher PKA volume can rapidly deprotonate the ligand, which would lead to rapid nucleation and the small particle size of ZIF-8 material.

The influence of the reaction time has been also investigated using five different modulators. And today, I'm going to show you the results related to a trimethylamine with zinc nitrate hexahydrate. The reaction time was 5, 10, 13, and 16 minutes. X-ray diffraction of these results confirm the intensity of the permanent peak increases as the reaction time increases as well. And this indicate that the material or a longer reaction time would lead or result in larger particle size.

However, the presence of sharp peaks, even for the reaction that have been done, and five minutes confirmed that these material can be successfully synthesized in a short period of time. Furthermore, to confirm the absence of the presence of zinc oxide as an impurity or byproduct of this material, the peaks between the area between-- the peaks in this area between 30 and 40 2-theta degree have been matched with the reflection from the resulting material.

And as you can see here, the peaks that belong to the simulated zinc oxide are not matching the peaks from the resulting material, confirming the absence of this material. However, all of the reflections that are obtained or from the simulated ZIF material are perfectly matching the peaks or reflections that are obtained from the resulting material, confirming the purity of the material and confirming that the material are pure ZIF-8. TM results also confirm that all of these material are punch material, even the material that synthesized a shorter time or five minutes.

And as you can see here, as we go from 5 minutes to 16 minutes, the particle size getting larger and larger. And this, by this, we confirm that longer reaction time would lead to a larger particle size, and the branch material can successfully synthesize in a short time of five minutes. Influence of zinc sources has been also studied.

So in this case, I used six different reactive zinc sources. But today, I'm going to show you the result of the three zinc sources, which are zinc iodide, zinc bromide, and zinc nitrate hexahydrate, obtained from trimethylamine or from n-butylamine. As you can see here, as we go from the least reactive zinc source, which is zinc iodide, into the larger or higher reactive zinc source of zinc nitrate hexahydrate, the particle size getting smaller. And also, we can see the differences between the-- and the morphology amine.

So this can be attributed to that in case of zinc nitrate hexahydrate, the amount of zinc ion that are available for the action is huge, which would lead to large amount of nuclide. And these nuclide can only grow up until a smaller particle size because of the rapid reduction and the super saturation solution.

So as this reaction have been repeated also with different zinc sources, we confirm that the reactivity of zinc precursors can directly assembly of ZIF-8 nanocrystals. And as you can see here, we observed that there was a reverse relationship between the particle size of the ZIF-8 material and the reactivity of zinc sources.

Furthermore, to confirm that our method would work with other ZIFs, I tried this method-- I mean, the addition of the modulator with other ZIF material. So I have tried it with ZIF-67 by using the same condition. And instead of using zinc nitrate, I used cobalt nitrate nuclide to obtain this material.

And the results confirming that using five different modulator would result in a branch material, confirming that our synthesis procedure could work with other ZIF material. However, the main differences between ZIF-67 and ZIF-8 is the particle size. While the ZIF-67 was the larger particle size, the ZIF-8 was the smaller particle size.

Furthermore, the BET surface area of these material confirm that the presence of microporous material and mesoporous material due to the presence of a combination isotherm type 1 and type 4 as well, which confirms the presence of both the microporous material and mesoporous material.

The X-ray diffraction confirmed this purity of this material and confirmed that this material is pure, the 67. And whatever question that I have for ZIF-8, I had it here, and I tried different condition. And more or less, I got the same trend or the similar result out ZIF-67 and ZIF-8. So by this, I kind of answering the inquiries that I have. And it is the time to study the structural effect of MOF material on that permeation by a mixed matrix membrane.

The typical or basic polymer that I had to use in this regard is 6 F DA-DAM. I use this polymer because this polymer poses thermal and chemical stability and showed good gas operation performance. And I have chosen three different morphologies. First morphology is ZIF. It's rhombic dodecahedron with larger particle size that can be constructed from zinc nitrate hexahyrdate without the addition of a modulator.

I also chose rhombic dodecahedral particle size with the smaller particle size imine that are constructed from zinc bromide with a trimethylamine. The branch material that I chose is constructed from zinc nitrate hexahyrdate with the trimethylamine. As you can see here, all of these material possess very different morphologies. They possess the similar lattice structure of ZIF-8 material.

The main differences of this material is the intensity and the broadening of the peak. And these could be related to the particle size of the material. The more the BET surface area are comparable except for branch material. As we can see here, there is a combination of the isotherm type 1 and type 4 characteristic for micro and mesoporous material.

So incorporating these particles with the polymer would result in different mixed matrix membranes. While the branch material can form transparent with no color film, the other materials-- I mean, the RBZ material, either the smaller particle size or larger particle size, which are more opaque-- either white or yellowish color membrane material. The intensity, the thickness also of these membranes also increases as the particle size increases from the smaller branch material particle size to the larger rhombic dodecahedral size.

Furthermore, in order to see how these morphologies distributed inside this membrane, the cross section SEM took place, though for the rhombic dodecahedral with larger particle size, we can see ZIF material settling nicely within the polymeric matrix. However, in case of the RDZ with the smaller particle size, we can see here the agglomeration of the smaller particles of these material. And the morphology here is like a gray structure or morphology.

For the branch material, we can't really distinguish between the ZIF material and polymeric matrix, which indicates a good adhesion of MOF material or of this pillar and the polymeric matrix. A cross section focus ion beam also shows that a wide size distribution between 13 nanometer to a 300 nanometer obtained from RDZ with larger or smaller particle size. And this can be attributed to the agglomeration of these particles. However, in case of punch material, we can see uniform dispersion across the entire film.

And the blastization resistance of ZIF-8 of these morphologies have been studied as well. And as you can see here, this is the typical blastization care for the polymer itself. And as you can see here, at the beginning, or initially, there is-- the permeability decreases up to 200 PSI due to the absorption mode. And then the permeability significantly increases. And this actually unwanted behavior of the polymers, because this behavior indicates that the universe starts to swell the CO2 gas, which would negatively affect its performance in the real application.

However, incorporation of the RBZ with either larger or smaller particle size, we can see some reduction of this behavior. More incorporation of these material would be, like I said, via the up-turned curve, which indicate the incorporation of the RBZ, either with larger or smaller particle size and with high MOF loading would result in-- I mean, would increase the blastization resistance.

However, in case of the punch material, incorporation even of small amounts of these material would result in the absence of this upturn curve, indicating that the branch material significantly increases the blastization resistance. Furthermore, selectivity of this material, of hydrogen over nitrogen, also enhanced for the ZIF material-- I mean, for RDZ with the larger particle size compared to the pure polymer.

So the selectivity here and permeability increases as we increase the MOF loading. Over for the RDZ with smaller particle size, we can see that there is enhancement of the selectivity of hydrogen over the nitrogen when the permeability, especially for 30 and 40 with percentage of MOF loading become-- may be the same.

The selectivity and the permeability of branch material with smaller particle size, however enhanced this can be attributed to the branch material form something like collation network bearing to the larger particle size. So these larger particle size cannot be attached to each other to form these kind of these channels as well.

So they have obtained the same trend for the selectivity of the hydrogen over methane as well. And by this, we confirm that a busy material, which showed great gas separation performance comparing to RDZ with either smaller or larger particle size. So in this case, I would like to conclude part of the presentation by that. Synthetic conditions would play a significant role in controlling the size and morphology of ZIF-8 material. And in order to obtain a smaller particle size and enhance the gas separation, you can either use a modulator with higher PKA value, shorter reaction time, and the more reactive zinc source.

We also see the differences between the RDZ with larger or smaller particle size and the branch material. And we have been seeing that the branch material would show uniform dispersion across the entire field, and that would increase the permeability and selectivity as well as the resistance to the CO2 blastization.

Beside the research work, I have completed several executive management and leadership program from Sloan School, and I have obtained the certificate in strategy and innovation. I've also completely completed several courses in different area, as well as I try to enhance my leadership, communication, and mentoring skills by attending different webinar series.

I have been trained also on several advanced analytic technique in order to characterize my samples, not only here at MIT, but also at Saudi Aramco. And I have attended a course, and we are about to publish a manuscript with the other team. And I would like to thank Professor Smith for accepting me to work under his supervision. And actually, I would like to thank him for the his advice and support, especially during the pandemic period. And actually, I feel that I'm lucky to work under his supervision and under this-- I mean, in such a healthy environment in his lab.

I also want to thank everybody in the group here for making my journey at MIT more enjoyable. I also want to thank the IBK and the KACST, because without you, I wouldn't be here today. So a special thanks, also, to Saudi Aramco, Aramco Americas, and MIT Energy Initiative. Thank you.

DOROTHY HANNA: Thank you so much, Fatima, for that excellent presentation. It's certainly been a pleasure on the IDK side getting to know you this past year and a half. So it's great to hear all about your work. And I'm going to open the floor for questions. Please feel free to unmute and ask a question or put a question in the chat, and we'll go from there. Kamal, please go ahead.

KAMAL YOUCEF-TOUMI: Yeah, thank you, Dorothy. Thank you, Fatima, for the great presentation. I learn a lot in all of these presentation and definitely because I have learned many things. This is outside my area.

I have three questions, if it's OK, Dorothy and Fatima. So one is on the modulator that you talked about. The second one was the reaction time. And the third one would be on the scale up and perhaps the cost in comparison to others.

So the first one is on the modulator. I think your results show very clearly about the influence that the effect of the modulator as you use it. Yes, exactly. This slide, we show the size of the particles will end up in the smaller, not only the size, but it looks like also the shape has been affected.

So in the end, for the permeability function of this material, I just want to understand. So as you clearly stated that the size plays a role. The shape plays a role. And in the end, the uniformity. How uniform this configuration is. What is the role of that, and if the uniformity in the sizes of the spaces between these particles that have to be a certain way, what is in there that allows this to happen in that way? Or you have to do some additional tweaking to it?

FATIMA ADHAIM: OK. So the permeability, as I showed you, increases as the material being branched comparing to the single crystals. So in this case, the branch material makes something like channel, and we call it a percolation network. And this would enhance the permeability of the gases.

However, in the case of the particle size or uniformity of the particle size, as you can see here, for example, there is a range of the particle size over all of these particles are able to form this kind of channel, comparing to this material, which form a uniform particle shape. And actually, because these particles are apart from each other, they are not able to form this kind of connection, and hence, this would affect the permeability of the material. So the uniformity in this case wants to play the significant rule. But the connectivity of the particle itself would have this rule or would control the permeability of the material.

And as I have showed you, as we increase the MOF loading, the permeability become more and would increase. And this also because more connections would be appeared or would be available in this case and more network can be obtained by increasing the MOF loading, I mean. So as we increase the MOF loading permeability, we are forming more networking, more-- I mean, more percolation at work, and we increase the permeability.

KAMAL YOUCEF-TOUMI: Great. Thank you. The other question had to do with the reaction time. And if I understand correctly, I think you mentioned that if the reaction thing is longer, and more experiments you had from 5 to 10 to 30 to 60 minutes that the size also became smaller. So yeah. And I wanted to understand. You were talking intensity versus degrees, and I didn't understand what that-- was it an angle or something.

FATIMA ADHAIM: OK.

KAMAL YOUCEF-TOUMI: For the degrees. So basically, just the graph. And then the other thing is that the matching or the mismatching of the peaks, of these curves. One thing you mentioned, I think, in your presentation was about the purity of the material that was part in this graph. And if you can just elaborate a little bit on that.

FATIMA ADHAIM: OK. So usually, from the X-ray diffraction, if you have a nanoparticle and small particle, we usually have broadening and the peak itself. So the broadening of the peak would indicate the presence of two things. Either amorphous material or nanoparticles, the size of the material.

And here, for the reaction-- I mean, the reaction that lasted in 60 minutes. We can see the green peak here. The intensity and the sharpness of the green peak is much higher, for example, than the material that synthesized for 5 minutes.

So the black-- if we compare the black curve here in terms of the broadening and the intensity, we can see that the material that synthesized for 60 minutes was just stronger and sharper peak, which indicate that the material is getting larger. However, as I have mentioned, the broadening of the peak indicating that the material is getting smaller, and this is what we've got here. And definitely, this material are not so amorphous material because even for shorter reaction time, we can see these peaks are matching with the simulated button of the ZIF-8 material.

On the other case, you are asking about the purity of this material. Yes, for the material synthesize for 60 and 30 minutes, we see these peaks our sharps. And in this case, I was wondering whether there is a impurity and the key to the presence of these sharp peaks in this case or not. So I was wondering if zinc oxide as presented within the framework of the material or not.

And as you can see here, when I try to match the piece of zinc oxide, it is not matching at all with the reflections from the resulting material, which indicate the absence of this impurity.

AUDIENCE: Yeah. Thank you, Fatima. I was just looking also at my notes, and I saw scribbles that I made when you were talking. This was on slide 14, if you don't mind. And I'm asking because I wanted to understand. So yeah. So these graphs that you have, the quantity absorbed on the vertical axis. And then the real axis, you have the pressure.

And it looks like different behavior. So for example, in the middle graph, you have the high absorption-- very quick. Right? Like very quickly like at slightly lower relative pressures. And then it kind of levels off. So that is one.

And then on the graph above it, it gives you the same, kind of the same behavior. But when you start reaching, like, about 1 in the relative pressure, then it starts going up, right?

FATIMA ADHAIM: Yeah.

KAMAL YOUCEF-TOUMI: And then the bottom plot has also kind of the same feature or the same look in the sense that it goes up very quickly or lower the pressure. And then the slopes seem to be approximately the same. And then when you reach about 0.7 or so, so at that time, it looks like another behavior is happening.

So this attracted my attention. And so if you can maybe just explain what is happening that is making these behaviors. At least to me, it looks like something interesting behaviors. Yeah.

FATIMA ADHAIM: OK. So for this title, the isotherm, the typical isotherm for the microporous material, it should be like this one. Just a moment. Give me a moment. OK. The behavior-- I mean, the typical isotherm of the microporous material should be isotherm type 1, and it should be like this.

However, the presence of this increasing, or this behavior, I mean, that indicates the material poses ultra-microporous material plus the microporous material. So for example, the microporous material should be less than 2 nanometer. However, the ultraporous material is the material that posses a smaller particle size up to 0.7 nanometer.

So the microporous material indicates a smaller pore size and inside it. And this would lead to this kind of the behavior. However, for the mesoporous material, usually possess this hysteresis loop. So before that, I would say we have here the same behavior of the isotherm type 1, which indicates the presence of microporous material.

However, the presence of this behavior, and we call it the hysteresis loop, this indicates the presence of larger particles and larger pore size. And it has the mesoporous material, which is larger than 2 nanometer, up to 15 nanometer. And from the shape of the particle size-- of the hysteresis loop, I mean-- we can predict the shape of the pore itself. And this is type I cylindric pore shape. So this is--

KAMAL YOUCEF-TOUMI: Yeah, this is interesting when you mentioned that hysteresis loop. So this means that the test was done in two different directions. Is that correct?

DOROTHY HANNA: No. No. We use the-- the same parameter has been-- I mean, the same conditions has been used for all of these citrine materials. But the behavior of the material, the non-particles-- I mean, the presence of mesoporous material here within the branch ZIF material that indicates these material-- actually, the pores here is like interconnected pores because of the agglomeration of the smaller particles, and this would lead to this kind of behavior.

So the same conditions have been applied for all of these material. But of the material consists of only microporous that would give this kind of the isotherm. However, there is ultra microporous for us. We will get this type of the isotherm, which it is the same. Isotherm type 1 for microporous materials. And if we have both, we get to get a combination isotherm.

KAMAL YOUCEF-TOUMI: So I don't know whether this applies or not. But in our case, from the mechanical engineering point of view, for processes or behaviors that show something that looks like a hysteresis or a hysteretic effect that you mentioned. So in that case, in that process, that means there are at least two things happening. One is the storage of energy, of potential energy. We think there are maybe some kind of elastic behavior. Or the fundamental debt.

And then the other one is the dissipation of loss of energy. And the bigger the loop in what looks like a hysteresis behavior, that means you have more losses there. That you have energy that is being applied into the system of power that is injected. And then there's more dissipation, so the loops become bigger.

So when the loops are smaller, we this dissipation. But in the end, you have to have at least one behavior or phenomena that is storing the potential energy or the equivalent of that. And then the other one is the least efficient of energy. And also, you have to be present together to show or describe this hysteretic behavior.

And then for systems that are purely elastic, then you will see only about one curve that has no roots in it. And then your graph, you're plotting some kind of a pressure versus the quantity absorbed, which is-- yeah. So anyway, when we look at these variables from that point of view, so we have this kind of-- so anyway, this is what came to my mind when you were describing. Whether it is related or maybe completely incorrect what I'm saying. for what is happening in your membranes. But at least from the behavior or the hysteresis and hysteretic behavior, what I mentioned is at least [INAUDIBLE].

FATIMA ADHAIM: Actually, in my case, I usually get this type of the isotherm-- I mean type 1 and 4-- when I'm going go from the single crystal or rhombic dodecahedral to branch material. So most of the branch materials shows this behavior to indicate that most of the branch material-- or actually, all of them-- possess both morphology or, I mean, both pores-- micro and meso.

KAMAL YOUCEF-TOUMI: Yeah. So anyway, so this is-- so the other thing that, when I look at plots like this, what comes to my mind is maybe more than one domain, like more than one energy domain is active in these experiments. So the relative pressure is affecting some kind of-- the fluidic side, like the gas in the end can be thought of as a fluid.

So that is the one domain. And then the other domain is that the particles themselves, looking at the material, perhaps, in some kind of elastic membrane. Anyway, I'm sorry that things are going in my mind in all these different directions. So thank you.

Just one last question, Fatima. So I think in the end, you know, this is the rate, of course, for using it in, I'm sure, many other applications, but definitely for the separation, gas separation. So what are the thoughts of maybe the team in Zach's group know about the scale up and the cost associated with that in comparison with these other methods that you have mentioned at the beginning of your presentation? I'm sure that this method that you guys are using in development has advantages also in that respect.

FATIMA ADHAIM: So what's the question again?

KAMAL YOUCEF-TOUMI: So I'm assuming that the experiments and all that are being done at this time maybe are in the lab, maybe at a smaller scale. And sometime in the near future, maybe this will be adapted or applied to a large scale separation process, and so on. And so I was curious about, when we go to that stage and one compares, let's say, the existing methods, or perhaps other competitive methods that are being developed or being used, and one looks at them from this point of view on the scale up, and maybe the cost that may be associated with them-- just a general thing.

FATIMA ADHAIM: Yeah, I agree with you. Actually, we gave a shot in our lab to scale up this material in order to obtain larger amounts. I mean, we usually synthesize this material in a small amount until we gave the shot to synthesize this material in order to obtain at least half a gram.

But we faced some issue of the scale up. And I think the team that I'm working with are working on this to develop a new method that can give us the same trend, but with more amount of the material.

KAMAL YOUCEF-TOUMI: Thank you. Thank you, Fatima.

FATIMA ADHAIM: Thank you.

KAMAL YOUCEF-TOUMI: Thank you for the presentation. I learned a lot today. Yeah, thank you.

FATIMA ADHAIM: Thank you.

DOROTHY HANNA: We have a couple more questions in the chat. Well, both say, congratulations on the talk, Fatima. And first one is back. A question about slide 14. Find your way there.

FATIMA ADHAIM: OK.

DOROTHY HANNA: Why are you using different precursors, ZMBR 2 and ZN NO2 in slide 14?

FATIMA ADHAIM: In order to see the differences or the effect of the particle size. I usually-- I mean, usually, without using any modulator, we get our own dodecahedral or single crystals. But in case of zinc bromide, which is the least reactive zinc source, the trimethylamine, which possess the smaller PKA value, give me also a branch-- I mean, single crystals from dodecahedral.

But the crystal in this case is smaller than the crystal that's presented with the material or constructed from the material that synthesized without the modulator. However, the addition of the modulator, same modulator with trimethylamine with zinc nitrate, which is high reactive zinc source, would result in a branch material. That's why I use-- I prefer to compare them between the large particle singular crystal, smaller particle single crystal rhombic dodecahedral, and branch material in terms of the gas permeability and selectivity.

DOROTHY HANNA: Thank you. Any other questions for Fatima? And I'm seeing lots of congratulations and good jobs, Fatima, pouring in through the chat. So very, very good work. Zach, would you like to add anything?

ZACH SMITH: I think it's a really good overview on the work that Fatima did. I was just wondering from a very high-level perspective-- we've got a couple of minutes-- maybe you could describe what surprised you most about making these materials. You looked at many, many variables. Which one gave you a result that you didn't anticipate when you first started?

FATIMA ADHAIM: OK. Actually, I did the mixed matrix membrane with ZIF-67 as well. And when I made this material, I thought that I'm going to have higher selectivity and permeability out of this mixed matrix membrane. And this is more or less similar to the already published work.

And in my case, actually, I got the opposite. I see that the permeability of the ZIF-67 is higher than ZIF-8, but the selectivity is lower. And I'm still thinking about-- I mean, I have to investigate more and see what is the reason behind this behavior.

ZACH SMITH: Very good. It's the next step for another study to come.

FATIMA ADHAIM: Yeah.

DOROTHY HANNA: Well, I think we will wrap things up there. Thank you very much, everybody, for joining us today. Thank you, Fatima. Great job.