The atmospheric concentration of carbon dioxide has been rising extensively since the Industrial Revolution and has now reached dangerous levels, contributing to climate change. Direct transformation of abundant CO2 to valuable chemicals and fuels is currently of great importance from the viewpoints of environmental and green chemistry. Utilization of CO2 as feedstock for methanol synthesis is one of the possibilities. Metal-organic frameworks (MOFs) have recently gained attention as potential catalysts in many reactions. Owing to crystalline nature, chemical tunability, remarkably high surface area and regular pore structure, MOF materials combine some of the best features of homogeneous and heterogeneous catalysts.
Our work deals with synthesis of MOFs containing cerium cations, of UiO-66 and MOF-808 topology, that could be used as catalyst in reactions allowing CO2 conversion. According to very good redox properties of cerium, its introduction to MOF structure is a chance to improve both the adsorptive and catalytic properties of parent material. Moreover, Ce-based MOFs containing Ce on +3 and +4 oxidation state can be considered bifunctional because Ce4+ cations act as Lewis acid sites, while Ce3+ act as Lewis basic sites responsible for adsorption of CO2.
In presented work we would like to demonstrate the influence of synthesis method on the physico-chemical properties of Ce containing MOFs and their ability to adsorb (reversibly and irreversibly) CO2. The impact of synthesis parameters on crystallographic structure (XRD), composition (XPS, IR), textural properties (N2 sorption), morphology (SEM), thermal stability (TGA), and CO2 sorption capacity of these materials will be presented. Moreover, the results of catalytic tests of CO2 hydrogenation to methanol over selected MOFs will be shown.