Two comparable Ba-MOFs with similar linkers for enhanced CO2 capture and separation by introducing N-rich groups

Abstract

Two new different metal–organic frameworks (MOFs) [Ba(L1)(H2O)2]n·nH2O (MOF 1) and [Ba(L2)(H2O)2]n·0.5nDMF·0.5nH2O (MOF 2) were yielded by the assembly of oxygen-friendly Ba(II) ions and two similar linkers, namely 2-(imidazol-1-yl)terephthalic acid (H2L1) and 2-(1H-1,2,4-triazol-1-yl) terephthalic acid (H2L2). Single-crystal X-ray diffractions (XRD) indicate that MOF 1 is a new three-dimensional (3D) stacking dense network formed by the one-dimensional (1D) rod-shaped chains and L1 linkers, whereas MOF 2 presents a 3D nanotube porous framework with cylindrical tunnels based on the 1D loop chains as the secondary building units (SBUs) by replacing the imidazole group in H2L1 with the triazole group in H2L2. As a result, MOF 2 has a higher density of active sites and Lewis acid sites in the porous surface of nanotube than MOF 1. Thereby, the CO2 capture and separation capacity of MOF 2 is great higher than that of CH4 at 298 K.