The modified MOF-74 with H2 dissociation function for CO2 hydrogenation: A DFT study

Abstract

MOF-74 has superior adsorption ability for CO2 and H2. In this work, we derived the properties of CO2 adsorption and H2 dissociation in the modified MOF-74 by density functional theory calculations, and preliminarily studied the first step of CO2 hydrogenation to methanol on them. The calculation results showed that there were three types of adsorption sites for CO2 adsorption on 14 M-MOF-74 materials with different transition metals as metal sites. CO2 was easier to be activated in the configuration that both C and O atoms interact with the metal sites. The five M-MOF-74 (M = Zr, Hf, Mo, W, Os) materials were found to have better performance for CO2 activation. After this, by analyzing the properties of H2 adsorption and dissociation, we found unsaturated metal sites in W-MOF-74 and Os-MOF-74 had distinctive ability for H2 dissociation and CO2 activation. Moreover, we investigated the reactivity of CO2 hydrogenation and protonation on W-MOF-74 and Os-MOF-74. Compared with Os-MOF-74, W-MOF-74 showed better performance in CO2 hydrogenation reaction, and CO2 adsorbed on W metal sites were more inclined to generate HCOO* intermediate. Based on these results, W-MOF-74 with the H2 dissociation function was suggested to have excellent activity for CO2 hydrogenation.