Research on the mechanism and application of rigid and flexible metal-organic frameworks in selective adsorption

Abstract

Metal-organic frameworks (MOFs) are materials with porousness that metal ions and organic bridging ligands make up the composition to join. They are commonly employed in gas separation applications because of their extraordinarily high sorption capacities and complicated sorption behaviour. This article mainly introduces the mechanism and application of rigid and flexible MOFs used in selectively separating various gases. Rigid MOFs are just standard MOFs with rigid backbones and porous frameworks that are comparably stable and strong. Based on molecular sieving effect, interactions between adsorbates and surfaces, and the cooperative effects of size/shape exclusion and adsorbate-surface interactions, rigid MOFs used in selective adsorption of H2, O2, CH4 were highlighted. For flexible MOFs, the crystalline order of the underlying coordination network is combined with cooperative structural transformability in them. Based on size/shape exclusion, adsorbate-surface interactions and gate-opening or structural rearrangement caused by adsorbate-surface interactions, gate-opening forces that are particular to each gate, flexible MOFs used in selective adsorption of C2H2, CO2 and CH4 were discussed.