Abstract:Nanoparticles of zeolitic imidazolate framework-7 (nZIF-7) were blended with poly(ether imide) (PEI) to fabricate a new mixed-matrix membrane (nZIF-7/PEI). nZIF-7 was chosen in order to demonstrate the power of postsynthetic modification (PSM) by linker exchange of benzimidazolate to benzotriazolate for tuning the permeability and selectivity properties of a resulting membrane (PSM-nZIF-7/PEI). These two new membranes were subjected to constant volume, variable pressure gas permeation measurements (H, N, O, CH… Show more
“…[8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] The key factor in the rational design of novel adsorbents is to tune their structural/chemical features to favor an equilibrium and/or kinetic separation or a full molecular sieving. [25][26][27][28][29][30][31][32] A very promising class of custom-designed inherently modular sorbents to achieve efficient gravimetric uptake and high CO 2 selectivity, combined with a low regeneration cost under practical conditions, is the class of metal-organic framework (MOF) materials. [33][34][35] These materials are being developed by connecting metal-containing units (ions or clusters) with organic linkers in order to create open crystalline frameworks with permanent porosity.…”
The adsorption of carbon dioxide and its separation from mixtures with methane using the recently synthetized SIFSIX-2-Cu-i metal-organic framework has been systematically studied by employing a variety of molecular simulation techniques. Quantum density functional theory calculations have been combined with force-field based Monte Carlo and molecular dynamics simulations in order to provide a deeper insight on the molecular-scale processes controlling the thermodynamic and dynamic adsorption selectivity of carbon dioxide over methane, giving particular emphasis on the mechanisms underlying the diffusion of the confined molecules in this porous hybrid material. The diffusion process was revealed to be mainly controlled by both (i) the residence dynamics around some specific interaction sites of the fluorinated metal-organic framework and (ii) the dynamics related to the process where faster molecules overtake slower ones in the narrow one-dimensional channel of SIFSIX-2-Cu-i. We further unveil a 1-dimensional diffusion behavior of both carbon dioxide and methane confined in this small pore MOF where single file diffusion is not observed.
“…[8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] The key factor in the rational design of novel adsorbents is to tune their structural/chemical features to favor an equilibrium and/or kinetic separation or a full molecular sieving. [25][26][27][28][29][30][31][32] A very promising class of custom-designed inherently modular sorbents to achieve efficient gravimetric uptake and high CO 2 selectivity, combined with a low regeneration cost under practical conditions, is the class of metal-organic framework (MOF) materials. [33][34][35] These materials are being developed by connecting metal-containing units (ions or clusters) with organic linkers in order to create open crystalline frameworks with permanent porosity.…”
The adsorption of carbon dioxide and its separation from mixtures with methane using the recently synthetized SIFSIX-2-Cu-i metal-organic framework has been systematically studied by employing a variety of molecular simulation techniques. Quantum density functional theory calculations have been combined with force-field based Monte Carlo and molecular dynamics simulations in order to provide a deeper insight on the molecular-scale processes controlling the thermodynamic and dynamic adsorption selectivity of carbon dioxide over methane, giving particular emphasis on the mechanisms underlying the diffusion of the confined molecules in this porous hybrid material. The diffusion process was revealed to be mainly controlled by both (i) the residence dynamics around some specific interaction sites of the fluorinated metal-organic framework and (ii) the dynamics related to the process where faster molecules overtake slower ones in the narrow one-dimensional channel of SIFSIX-2-Cu-i. We further unveil a 1-dimensional diffusion behavior of both carbon dioxide and methane confined in this small pore MOF where single file diffusion is not observed.
“…In particular, BUCT-2-based MMMs exhibited the best performance with a CO 2 permeability of 635.1 barrer and a CO 2 /N 2 selectivity of 41.8. These characteristics exceeded the values reported for similar materials elsewhere and almost surpassed the upper-bound limits for polymer-based membranes for CO 2 /N 2 separation ( Figure 4 B and Table S10 ) ( Al-Maythalony et al., 2017 ; Bae and Long, 2013 ; Ding et al., 2020 ; Li et al., 2016 ; Nafisi and Hägg, 2014 ; Song et al., 2012 ; Su et al., 2016 ; Xin et al., 2015 ). Figure 4 Gas separation performances of BUCT-MOF-based mixed matrix membranes (A) Comparison of gas separation performances of MMMs prepared from BUCT MOFs, MOF-508, and the pristine polymer membrane.…”
Summary
The preparation of flawless and defect-free mixed matrix membranes (MMMs) comprising metal-organic framework (MOF) and polymer is often difficult owing to the poor MOF/polymer interface compatibility. Herein, we present the synthesis of an important family of pillared-layered MOFs with polymerizable moieties based on the parent structure [Zn
2
L
2
P]
n
[L = vinyl containing benzenedicarboxylic acid linkers; P = 4,4′-bipyridine (bipy)]. The crystalline structures of polymerizable MOFs were analyzed using single-crystal X-ray crystallography. The presence of reactive double bonds in MOFs was verified by the successful thiol-ene click reaction with sulfhydryl compounds. The subsequent copolymerization of polymerizable MOFs with organic monomers produced mixed matrix membranes with enhanced MOF/polymer interfacial adhesion that enabled good separation efficiency of CO
2
from flue gas. This strategy provides a stimulating platform to the preparation of highly efficient MMMs that are capable of mitigating energy consumption and environment issues.
“…However, at higher loading (34 wt.%) polymer rigidification around the nanoparticles took place, positively affecting the selectivity (214% and 208% enhancement for CO 2 /CH 4 and CO 2 /N 2 , respectively), while the CO 2 permeability was considerably lower when compared to that of the neat polymer. Post synthesis modification of nanosized (40–70 nm) ZIF-7 was implemented by Al-Maythalony et al [ 73 ], aiming at tuning the pore size by exchanging the organic ligand, benzimidazolate with benzotriazolate. The synthesized nZIF-7 and PSM-nZIF-7 were embedded in a polyetherimide (PEI) matrix.…”
Application of conventional polymeric membranes in CO2 separation processes are limited by the existing trade-off between permeability and selectivity represented by the renowned upper bound. Addition of porous nanofillers in polymeric membranes is a promising approach to transcend the upper bound, owing to their superior separation capabilities. Porous nanofillers entice increased attention over nonporous counterparts due to their inherent CO2 uptake capacities and secondary transport pathways when added to polymer matrices. Infinite possibilities of tuning the porous architecture of these nanofillers also facilitate simultaneous enhancement of permeability, selectivity and stability features of the membrane conveniently heading in the direction towards industrial realization. This review focuses on presenting a complete synopsis of inherent capacities of several porous nanofillers, like metal organic frameworks (MOFs), Zeolites, and porous organic frameworks (POFs) and the effects on their addition to polymeric membranes. Gas permeation performances of select hybrids with these three-dimensional (3D) fillers and porous nanosheets have been summarized and discussed with respect to each type. Consequently, the benefits and shortcomings of each class of materials have been outlined and future research directions concerning the hybrids with 3D fillers have been suggested.
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