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1. Inverse CO ₂ /C ₂ H ₂ Separation with MFU‐4 and Selectivity Reversal via Postsynthetic Ligand Exchange

   https://doi.org/10.1002/ange.202218854  

   Liu, Qiao ; Cho, Sung Gu ; Hilliard, Jordon ; Wang, Ting‐Yuan ; Chien, Szu‐Chia ; Lin, Li‐Chiang ; Co, Anne C. ; Wade, Casey R. ( March 2023 , Angewandte Chemie)

   Although many porous materials, including metal–organic frameworks (MOFs), have been reported to selectively adsorb C₂H₂in C₂H₂/CO₂separation processes, CO₂‐selective sorbents are much less common. Here, we report the remarkable performance ofMFU‐4(Zn₅Cl₄(bbta)₃, bbta=benzo‐1,2,4,5‐bistriazolate) toward inverse CO₂/C₂H₂separation. The MOF facilitates kinetic separation of CO₂from C₂H₂, enabling the generation of high purity C₂H₂(>98 %) with good productivity in dynamic breakthrough experiments. Adsorption kinetics measurements and computational studies show C₂H₂is excluded fromMFU‐4by narrow pore windows formed by Zn−Cl groups. Postsynthetic F⁻/Cl⁻ligand exchange was used to synthesize an analogue (MFU‐4‐F) with expanded pore apertures, resulting in equilibrium C₂H₂/CO₂separation with reversed selectivity compared toMFU‐4.MFU‐4‐Falso exhibits a remarkably high C₂H₂adsorption capacity (6.7 mmol g⁻¹), allowing fuel grade C₂H₂(98 % purity) to be harvested from C₂H₂/CO₂mixtures by room temperature desorption.
2. Molecular dynamics simulations of a hydrophilic MIL-160-based membrane demonstrate pressure-dependent selective uptake of industrially relevant greenhouse gases

   https://doi.org/10.1039/d1ma00468a  

   Chapman, Jordan ; Garapati, Nagasree ; Glezakou, Vassiliki-Alexandra ; Duan, Yuhua ; Hu, Jianli ; Dinu, Cerasela Zoica ( September 2021 , Materials Advances)

   Continued integration of technologies capable of achieving higher degrees of sustainability while meeting global material and energy demands is of singular importance in halting human-caused climate change. Gas separation membranes composed of metal–organic frameworks (MOFs) are considered promising candidates for such integration; owing to their modular, scalable nature and high degree of tunability they are seen essential to maintain separation functionality. However, prior to sustainable implementation, both an evaluation of MOF characteristics and an intensive examination of MOF–gas molecule interactions are necessary to fully understand the fundamental separation criteria as well as to define suitable ranges of gas separation conditions. Herein, we present our findings on the greenhouse gas separation capabilities of the hydrophilic, Al-based MIL-160 in the selective uptake of carbon dioxide (CO 2 ) from other relevant greenhouse gases, i.e. , methane (CH 4 ), sulfur dioxide (SO 2 ), nitrogen dioxide (NO 2 ), and nitric oxide (NO), including gravimetric solubility, permeability, and diffusivity calculations. We found that a MIL-160 membrane has excellent applicability in the separation of gases of varying electronegativities, with a diffusivity selectivity of 72.0, 9.53, and 13.8 for CH 4 , NO 2 , and NO, respectively, relative to CO 2 . Further,more »we demonstrate that the selectivity at which gas molecules diffuse through the MIL-160 membrane varies strongly with the simulation pressure, suggesting that such membrane system is potentially an ideal candidate for the development of pressure-swing adsorption processes that achieve gas separations efficiently while mitigating the emission of greenhouse gases.« less
3. Identifying promising metal–organic frameworks for heterogeneous catalysis via high‐throughput periodic density functional theory

   https://doi.org/10.1002/jcc.25787  

   Rosen, Andrew S. ; Notestein, Justin M. ; Snurr, Randall Q. ( February 2019 , Journal of Computational Chemistry)

   Metal–organic frameworks (MOFs) are a class of nanoporous materials with highly tunable structures in terms of both chemical composition and topology. Due to their tunable nature, high‐throughput computational screening is a particularly appealing method to reduce the time‐to‐discovery of MOFs with desirable physical and chemical properties. In this work, a fully automated, high‐throughput periodic density functional theory (DFT) workflow for screening promising MOF candidates was developed and benchmarked, with a specific focus on applications in catalysis. As a proof‐of‐concept, we use the high‐throughput workflow to screen MOFs containing open metal sites (OMSs) from the Computation‐Ready, Experimental MOF database for the oxidative C—H bond activation of methane. The results from the screening process suggest that, despite the strong C—H bond strength of methane, the main challenge from a screening standpoint is the identification of MOFs with OMSs that can be readily oxidized at moderate reaction conditions. © 2019 Wiley Periodicals, Inc.
4. Fabrication of a freestanding metal organic framework predominant hollow fiber mat and its potential applications in gas separation and catalysis

   https://doi.org/10.1039/c9ta11701f  

   Dai, Zijian ; Lee, Dennis T. ; Shi, Kaihang ; Wang, Siyao ; Barton, Heather F. ; Zhu, Jie ; Yan, Jiaqi ; Ke, Qinfei ; Parsons, Gregory N. ( February 2020 , Journal of Materials Chemistry A)

   Recently, metal–organic framework (MOF)-based polymeric substrates show promising performance in many engineering and technology fields. However, a commonly known drawback of MOF/polymer composites is MOF crystal encapsulation and reduced surface area. This work reports a facile and gentle strategy to produce self-supported MOF predominant hollow fiber mats. A wide range of hollow MOFs including MIL-53(Al)–NH 2 , Al-PMOF, and ZIF-8 are successfully fabricated by our synthetic method. The synthetic strategy combines atomic layer deposition (ALD) of metal oxides onto polymer fibers and subsequent selective removal of polymer components followed by conversion of remaining hollow metal oxides into freestanding MOF predominant hollow fiber structures. The hollow MOFs show boosted surface area, superb porosity, and excellent pore accessibility, and exhibit a significantly improved performance in CO 2 adsorption (3.30 mmol g −1 ), CO 2 /N 2 separation selectivity (24.9 and 21.2 for 15/85 and 50/50 CO 2 /N 2 mixtures), and catalytic removal of HCHO (complete oxidation of 150 ppm within 60 min).
5. High-throughput computational prediction of the cost of carbon capture using mixed matrix membranes

   https://doi.org/10.1039/C8EE02582G  

   Budhathoki, Samir ; Ajayi, Olukayode ; Steckel, Janice A. ; Wilmer, Christopher E. ( January 2019 , Energy & Environmental Science)

   Polymeric membranes are being studied for their potential use in post-combustion carbon capture on the premise that they could dramatically lower costs relative to mature technologies available today. Mixed matrix membranes (MMMs) are advanced materials formed by combining polymers with inorganic particles. Using metal–organic frameworks (MOFs) as the inorganic particles has been shown to improve selectivity and permeability over pure polymers. We have carried out high-throughput atomistic simulations on 112 888 real and hypothetical metal–organic framework structures in order to calculate their CO 2 permeabilities and CO 2 /N 2 selectivities. The CO 2 /H 2 O sorption selectivity of 2 017 real MOFs was evaluated using the H 2 O sorption data of Li et al. (S. Li, Y. G. Chung and R. Q. Snurr, Langmuir , 2016, 32 , 10368–10376). Using experimentally measured polymer properties and the Maxwell model, we predicted the properties of all of the hypothetical mixed matrix membranes that could be made by combining the metal–organic frameworks with each of nine polymers, resulting in over one million possible MMMs. The predicted gas permeation of MMMs was compared to published gas permeation data in order to validate the methodology. We then carried out twelve individually optimized techno-economic evaluationsmore »of a three-stage membrane-based capture process. For each evaluation, capture process variables such as flow rate, capture fraction, pressure and temperature conditions were optimized and the resultant cost data were interpolated in order to assign cost based on membrane selectivity and permeability. This work makes a connection from atomistic simulation all the way to techno-economic evaluation for a membrane-based carbon capture process. We find that a large number of possible mixed matrix membranes are predicted to yield a cost of carbon capture less than $50 per tonne CO 2 removed, and a significant number of MOFs so identified have favorable CO 2 /H 2 O sorption selectivity.« less