Computational study of oxygen adsorption in metal–organic frameworks with exposed cation sites: effect of framework metal ions†
Abstract
The current inefficient separation of O2 from air is an important industrial problem. Metal–organic frameworks containing coordinatively unsaturated metal sites (CUS) have emerged as competitive new adsorbents for such targets. In this study, dispersion-corrected density functional theory calculations were performed to investigate the influence of framework metal ions on the adsorption behavior of O2 in M3(BTC)2-type materials (M = Cr, Mn, Fe, Co, Ni and Cu; BTC = 1,3,5-benzenetricarboxylate acid). The results show that Ni3(BTC)2 can be potentially considered as promising oxygen adsorbent with relatively easier deoxygenation than Cr3(BTC)2. The magnitude of charge transfer from the CUS to O2 molecule was found to have a significant impact on the interaction energies of O2 with M3(BTC)2 except for the Cu version. Furthermore, it was revealed that the origin of the difference in the charge transfer can be attributed to the different electronegativity of the metals.