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Insights into the Stability of Zeolitic Imidazolate Frameworks in Humid Acidic Environments from First-Principles Calculations
Understanding the degradation mechanisms of zeolitic imidazolate frameworks (ZIFs) is crucial to improve their chemical stability and realize their potential industrial applications. In this work, we conduct a comprehensive study utilizing dispersion-corrected density functional theory calculations to investigate the chemical stability of bulk ZIFs and their external surfaces under conditions of acid-gas exposure. We examine the influence of steric factors such as topology and ligand functionalization on the relative chemical stability of prototypical ZIFs (ZIF-2 and ZIF-8), including their hypothetical polymorphs. We find that defect formation is more thermodynamically and kinetically favorable at ZIF external surfaces versus the bulk, and that both topology and ligand functionalization impact defect formation. In addition, we provide a detailed mechanism for the reaction of ZIFs with sulfurous and sulfuric acids, of which the latter serves as a catalyst in potential degradation reactions of ZIFs. We also provide information about the adsorption strength of a range of acid gases to defective ZIF structures, which can inform potential strategies to regenerate ZIFs and/or achieve defect engineering in these materials.
Enzyme- and Relative Humidity-Responsive Antimicrobial Fibers for Active Food Packaging
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Influence of Humidity on Grip and Release Adhesion Mechanisms for Gecko-Inspired Microfibrillar Surfaces
Not provided.
Humidity-Controlled Preparation of Flexible Porous Carbon Fibers from Block Copolymers
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Humidity-Responsive Polymorphism in CALF-20: A Resilient MOF Physisorbent for CO 2 Capture
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Formaldehyde Emissions from Ventilation Filter Under Different Relative Humidity Conditions
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Carbon Dioxide Capture Chemistry of Amino Acid Functionalized Metal-Organic Frameworks in Humid Flue Gas
Here, metal-organic framework-808 has been functionalized with 11 amino acids (AA) to produce a series of MOF-808-AA structures. The adsorption of CO 2 under flue gas conditions revealed that glycine- and DL-lysine-functionalized MOF-808 (MOF-808-Gly and -DL-Lys) have the highest uptake capacities. Enhanced CO 2 capture performance in the presence of water was observed and studied using single-component sorption isotherms, CO 2 /H 2 O binary isotherm, and dynamic breakthrough measurements. The key to the favorable performance was uncovered by deciphering the mechanism of CO 2 capture in the pores and attributed to the formation of bicarbonate as evidenced by 13 C and 15 N solid-state nuclear magnetic resonance spectroscopy studies. Based on these results, we examined the performance of MOF-808-Gly in simulated coal flue gas conditions and found that it is possible to capture and release CO 2 by vacuum swing adsorption. MOF-808-Gly was cycled at least 80 times with full retention of performance. This study significantly advances our understanding of CO 2 chemistry in MOFs by revealing how strongly bound amine moieties to the MOF backbone create the chemistry and environment within the pores, leading to the binding and release of CO 2 under mild conditions without application of heat.
The Chemistry of CO 2 Capture in an Amine-Functionalized Metal–Organic Framework under Dry and Humid Conditions
In this paper, the use of two primary alkylamine functionalities covalently tethered to the linkers of IRMOF-74-III results in a material that can uptake CO 2 at low pressures through a chemisorption mechanism. In contrast to other primary amine-functionalized solid adsorbents that uptake CO 2 primarily as ammonium carbamates, we observe using solid state NMR that the major chemisorption product for this material is carbamic acid. Finally, the equilibrium of reaction products also shifts to ammonium carbamate when water vapor is present; a new finding that has impact on control of the chemistry of CO 2 capture in MOF materials and one that highlights the importance of geometric constraints and the mediating role of water within the pores of MOFs.
Humidity Sensing through Reversible Isomerization of a Covalent Organic Framework
Abstract not provided