Metal–Organic Framework with Functional Amide Groups for Highly Selective Gas Separation

A new three-dimensional microporous metal–organic framework [Cu­(<i>N</i>-(pyridin-4-yl)­isonicotinamide)₂(SiF₆)]­(EtOH)₂(H₂O)₁₂ (<b>UTSA-48</b>, UTSA = University of Texas at San Antonio) with functional −CONH– groups on the pore surfaces was synthesized and structurally characterized. The small pores and the functional −CONH– groups on the pore surfaces within the activated <b>UTSA-48a</b> have enabled their strong interactions with C₂H₂ and CO₂ of adsorption enthalpy of 34.4 and 30.0 kJ mol^–1, respectively. Accordingly, activated <b>UTSA-48</b> exhibits highly selective gas sorption of C₂H₂ and CO₂ over CH₄ with the Henry Law’s selectivities of 53.4 and 13.2 respectively, at 296 K, thereby, highlighting the promise for its application in industrially important gas separation

Exploring the Effect of Ligand-Originated MOF Isomerism and Methoxy Group Functionalization on Selective Acetylene/Methane and Carbon Dioxide/Methane Adsorption Properties in Two NbO-Type MOFs

Investigation of the impact of ligand-originated MOF (metal–organic framework) isomerism and ligand functionalization on gas adsorption is of vital importance because a study in this aspect provides valuable guidance for future fabrication of new MOFs exhibiting better performance. For the abovementioned purpose, two NbO-type ligand-originated MOF isomers based on methoxy-functionalized diisophthalate ligands were solvothermally constructed in this work. Their gas adsorption properties toward acetylene, carbon dioxide, and methane were systematically investigated, revealing their promising potential for the adsorptive separation of both acetylene/methane and carbon dioxide/methane gas mixtures, which are involved in the industrial processes of acetylene production and natural gas sweetening. In particular, compared to its isomer <b>ZJNU-58</b>, <b>ZJNU-59</b> displays larger acetylene and carbon dioxide uptake capacities as well as higher acetylene/methane and carbon dioxide/methane adsorption selectivities despite its lower pore volume and surface area, demonstrating a very crucial role that the effect of pore size plays in acetylene and carbon dioxide adsorption. In addition, the impact of ligand modification with a methoxy group on gas adsorption was also evaluated. <b>ZJNU-58</b> exhibits slightly lower acetylene and carbon dioxide uptake capacities but higher acetylene/methane and carbon dioxide/methane adsorption selectivities as compared to its parent compound NOTT-103. By contrast, enhanced adsorption selectivities and uptake capacities were observed for <b>ZJNU-59</b> as compared to its parent compound <b>ZJNU-73</b>. The results demonstrated that the impact of ligand functionalization with a methoxy group on gas adsorption might vary from MOF to MOF, depending on the chosen parent compound. The results might shed some light on understanding the impact of both ligand-originated MOF isomerism and methoxy group functionalization on gas adsorption

Exploring the Effect of Ligand-Originated MOF Isomerism and Methoxy Group Functionalization on Selective Acetylene/Methane and Carbon Dioxide/Methane Adsorption Properties in Two NbO-Type MOFs

Investigation of the impact of ligand-originated MOF (metal–organic framework) isomerism and ligand functionalization on gas adsorption is of vital importance because a study in this aspect provides valuable guidance for future fabrication of new MOFs exhibiting better performance. For the abovementioned purpose, two NbO-type ligand-originated MOF isomers based on methoxy-functionalized diisophthalate ligands were solvothermally constructed in this work. Their gas adsorption properties toward acetylene, carbon dioxide, and methane were systematically investigated, revealing their promising potential for the adsorptive separation of both acetylene/methane and carbon dioxide/methane gas mixtures, which are involved in the industrial processes of acetylene production and natural gas sweetening. In particular, compared to its isomer <b>ZJNU-58</b>, <b>ZJNU-59</b> displays larger acetylene and carbon dioxide uptake capacities as well as higher acetylene/methane and carbon dioxide/methane adsorption selectivities despite its lower pore volume and surface area, demonstrating a very crucial role that the effect of pore size plays in acetylene and carbon dioxide adsorption. In addition, the impact of ligand modification with a methoxy group on gas adsorption was also evaluated. <b>ZJNU-58</b> exhibits slightly lower acetylene and carbon dioxide uptake capacities but higher acetylene/methane and carbon dioxide/methane adsorption selectivities as compared to its parent compound NOTT-103. By contrast, enhanced adsorption selectivities and uptake capacities were observed for <b>ZJNU-59</b> as compared to its parent compound <b>ZJNU-73</b>. The results demonstrated that the impact of ligand functionalization with a methoxy group on gas adsorption might vary from MOF to MOF, depending on the chosen parent compound. The results might shed some light on understanding the impact of both ligand-originated MOF isomerism and methoxy group functionalization on gas adsorption

Exploring the Effect of Ligand-Originated MOF Isomerism and Methoxy Group Functionalization on Selective Acetylene/Methane and Carbon Dioxide/Methane Adsorption Properties in Two NbO-Type MOFs

Investigation of the impact of ligand-originated MOF (metal–organic framework) isomerism and ligand functionalization on gas adsorption is of vital importance because a study in this aspect provides valuable guidance for future fabrication of new MOFs exhibiting better performance. For the abovementioned purpose, two NbO-type ligand-originated MOF isomers based on methoxy-functionalized diisophthalate ligands were solvothermally constructed in this work. Their gas adsorption properties toward acetylene, carbon dioxide, and methane were systematically investigated, revealing their promising potential for the adsorptive separation of both acetylene/methane and carbon dioxide/methane gas mixtures, which are involved in the industrial processes of acetylene production and natural gas sweetening. In particular, compared to its isomer <b>ZJNU-58</b>, <b>ZJNU-59</b> displays larger acetylene and carbon dioxide uptake capacities as well as higher acetylene/methane and carbon dioxide/methane adsorption selectivities despite its lower pore volume and surface area, demonstrating a very crucial role that the effect of pore size plays in acetylene and carbon dioxide adsorption. In addition, the impact of ligand modification with a methoxy group on gas adsorption was also evaluated. <b>ZJNU-58</b> exhibits slightly lower acetylene and carbon dioxide uptake capacities but higher acetylene/methane and carbon dioxide/methane adsorption selectivities as compared to its parent compound NOTT-103. By contrast, enhanced adsorption selectivities and uptake capacities were observed for <b>ZJNU-59</b> as compared to its parent compound <b>ZJNU-73</b>. The results demonstrated that the impact of ligand functionalization with a methoxy group on gas adsorption might vary from MOF to MOF, depending on the chosen parent compound. The results might shed some light on understanding the impact of both ligand-originated MOF isomerism and methoxy group functionalization on gas adsorption

Microporous Metal–Organic Framework Stabilized by Balanced Multiple Host–Couteranion Hydrogen-Bonding Interactions for High-Density CO₂ Capture at Ambient Conditions

Microporous metal organic frameworks (MOFs) show promising application in several fields, but they often suffer from the weak robustness and stability after the removal of guest molecules. Here, three isostructural cationic metal–organic frameworks {[(Cu₄Cl)­(cpt)₄(H₂O)₄]·3X·4DMAc·CH₃OH·5H₂O} (<b>FJU-14</b>, X = NO₃, ClO_4, BF₄; DMAc = <i>N</i>,<i>N</i>′-dimethylacetamide) containing two types of polyhedral nanocages, one octahedron, and another tetrahedron have been synthesized from bifunctional organic ligands 4-(4<i>H</i>-1,2,4-triazol-4-yl) benzoic acid (Hcpt) and various copper salts. The series of MOFs <b>FJU-14</b> are demonstrated as the first examples of the isostructural MOFs whose robustness, thermal stability, and CO₂ capacity can be greatly improved via rational modulation of counteranions in the tetrahedral cages. The activated <b>FJU-14-BF</b>_<b>4</b><b>-a</b> containing BF₄^– anion can take CO₂ of 95.8 cm³ cm^–3 at ambient conditions with an adsorption enthalpy only of 18.8 kJ mol^–1. The trapped CO₂ density of 0.955 g cm^–3 is the highest value among the reported MOFs. Dynamic fixed bed breakthrough experiments indicate that the separation of CO₂/N₂ mixture gases through a column packed with <b>FJU-14-BF</b>_<b>4</b><b>-a</b> solid can be efficiently achieved. The improved robustness and thermal stability for <b>FJU-14-BF</b>_<b>4</b><b>-a</b> can be attributed to the balanced multiple hydrogen-bonding interactions (MHBIs) between the BF₄^– counteranion and the cationic skeleton, while the high-density and low-enthalpy CO₂ capture on <b>FJU-14-BF</b>_<b>4</b><b>-a</b> can be assigned to the multiple-point interactions between the adsorbate molecules and the framework as well as with its counteranions, as proved by single-crystal structures of the guest-free and CO₂-loaded <b>FJU-14-BF</b>_<b>4</b><b>-a</b> samples

Microporous Metal–Organic Framework Stabilized by Balanced Multiple Host–Couteranion Hydrogen-Bonding Interactions for High-Density CO₂ Capture at Ambient Conditions

Microporous metal organic frameworks (MOFs) show promising application in several fields, but they often suffer from the weak robustness and stability after the removal of guest molecules. Here, three isostructural cationic metal–organic frameworks {[(Cu₄Cl)­(cpt)₄(H₂O)₄]·3X·4DMAc·CH₃OH·5H₂O} (<b>FJU-14</b>, X = NO₃, ClO_4, BF₄; DMAc = <i>N</i>,<i>N</i>′-dimethylacetamide) containing two types of polyhedral nanocages, one octahedron, and another tetrahedron have been synthesized from bifunctional organic ligands 4-(4<i>H</i>-1,2,4-triazol-4-yl) benzoic acid (Hcpt) and various copper salts. The series of MOFs <b>FJU-14</b> are demonstrated as the first examples of the isostructural MOFs whose robustness, thermal stability, and CO₂ capacity can be greatly improved via rational modulation of counteranions in the tetrahedral cages. The activated <b>FJU-14-BF</b>_<b>4</b><b>-a</b> containing BF₄^– anion can take CO₂ of 95.8 cm³ cm^–3 at ambient conditions with an adsorption enthalpy only of 18.8 kJ mol^–1. The trapped CO₂ density of 0.955 g cm^–3 is the highest value among the reported MOFs. Dynamic fixed bed breakthrough experiments indicate that the separation of CO₂/N₂ mixture gases through a column packed with <b>FJU-14-BF</b>_<b>4</b><b>-a</b> solid can be efficiently achieved. The improved robustness and thermal stability for <b>FJU-14-BF</b>_<b>4</b><b>-a</b> can be attributed to the balanced multiple hydrogen-bonding interactions (MHBIs) between the BF₄^– counteranion and the cationic skeleton, while the high-density and low-enthalpy CO₂ capture on <b>FJU-14-BF</b>_<b>4</b><b>-a</b> can be assigned to the multiple-point interactions between the adsorbate molecules and the framework as well as with its counteranions, as proved by single-crystal structures of the guest-free and CO₂-loaded <b>FJU-14-BF</b>_<b>4</b><b>-a</b> samples

Monomer Symmetry-Regulated Defect Engineering: In Situ Preparation of Functionalized Covalent Organic Frameworks for Highly Efficient Capture and Separation of Carbon Dioxide

Developing crystalline porous materials with highly efficient CO2 selective adsorption capacity is one of the key challenges to carbon capture and storage (CCS). In current studies, much more attention has been paid to the crystalline and porous properties of crystalline porous materials for CCS, while the defects, which are unavoidable and ubiquitous, are relatively neglected. Herein, for the first time, we propose a monomer-symmetry regulation strategy for directional defect release to achieve in situ functionalization of COFs while exposing uniformly distributed defect-aldehyde groups as functionalization sites for selective CO2 capture. The regulated defective COFs possess high crystallinity, good structural stability, and a large number of organized and functionalized aldehyde sites, which exhibit one of the highest selective separation values of all COF sorbing materials in CO2/N2 selective adsorption (128.9 cm3/g at 273 K and 1 bar, selectivity: 45.8 from IAST). This work not only provides a new strategy for defect regulation and in situ functionalization of COFs but also provides a valuable approach in the design and preparation of new adsorbents for CO2 adsorption and CO2/N2 selective separation