The activation of Co-MOF-74 with open metal sites and their corresponding CO/N2 adsorptive separation performance
CO is an important raw material and the separation of CO/N 2 in blast furnace gas can supply an abundant source of CO. Metal organic frameworks (MOFs) containing open metal sites are capable of selectively binding to CO over N 2 . However, the open metal sites easily bind to guest molecules during the preparation and activation process. In this study, typical MOFs containing open metal sites (Co-MOF-74) were used to investigate the activation behavior and corresponding CO/N 2 adsorptive separation performance. To characterize the removal and decomposition of guest molecules, TG-MS and NMR analysis of MOF-74 prepared under different activation conditions were performed. During the heat and vacuum process, the guest H 2 O and methanol (MeOH) molecules in Co-MOF-74 were first removed at 150 °C under vacuum. The aim of high temperature activation at 300 °C is the decomposition of a small amount of bind N,N-dimethylformamide (DMF) and terminal ligands occupying the open metal sites in Co-MOF-74. In addition, H 2 O molecules occupy the open metal sites of Co-MOF-74 during the filtration and MeOH wash steps under air, which is accompanied by the removal of a portion of DMF. The CO adsorption (298 K and 1 bar) and the CO/N 2 selectivity (Ideal adsorbed solution theory: 50:50, v/v) of Co-MOF-74 activated at 300 °C was 6.07 mmol/g and 384, respectively, which was higher than that of the other activated Co-MOF-74 samples and was attributed to the effective removal of guest molecules. Our results may guide the activation of MOFs, which contain open metal sites.
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