Experimental research of alkali metals modified Mg/DOBDC metal organic framework as high capacity CO2 adsorbent

In this paper, novel M−Mg/DOBDC (M = Li, Na, K) composites (a MOF built of Mg(OAc)2·4H2O and MOAc (M = Li, Na, K) linked by 2,5-dioxido-1,4-benzenedicarboxylate (DOBDC) ligands) were prepared for the first time by doping alkali metals in Mg/DOBDC MOF. The CO2 dynamic adsorption performance of the novel synthesized composite was experimentally investigated, including different alkali metal doping amounts and alkali metal species. The structural morphology and CO2 adsorption of the composites were characterized by XRD, FT-IR, SEM, EDX, BET, CO2-TPD and TGA. Ten cycles of adsorption–desorption tests were performed on the M−Mg/DOBDC after doping with alkali metals. In addition, the CO2 adsorption process of the materials was simulated using various models. The results showed that the introduction of the alkali cation M+ would coordinate with the active site of the metal center and had high affinity and activation ability for CO2. The composite with the best dynamic CO2 uptake after the modification of Li, Na and K alkali metals was 0.5 K-Mg/DOBDC with an adsorption capacity of 14.93 mmol g−1 (0.1 MPa, 25 °C), which was 3.44 times higher than that of the parent material Mg/DOBDC. That was higher than the previously reported CO2 capture performance.