MOF-Based Nanocatalysts for Methanation of Carbon Dioxide and Carbon Monoxide at Ambient Pressure

Nowadays, finding catalysts that can perform the hydrogenation of CO2 and CO with high efficiency and selectivity has become a research challenge. So, in this report, two types of porous carbon nanostructures of CUiO-66 and CUiO-66-NH2 with high surface area, which both were obtained from two types of metal–organic frameworks (MOFs) of UiO-66 and UiO-66-NH2 as precursors, were used in the CO2 and CO hydrogenation after loading the active metal of nickel on their surface. The results of BET-N2 and CO2 adsorption showed higher surface area and adsorption capacity of the catalyst supports than those of their precursors. Also, the results of X-ray photoelectron spectroscopy (XPS) analysis indicated the presence of nitrogen-containing species such as pyridine in the structure of xNi@CUiO-66-NH2 catalysts, which can act as basicity sites in sorption of CO2 during the hydrogenation reaction, as was confirmed by results of CO2-temperature-programmed desorption. Among the catalyst samples with CUiO-66-NH2 and CUiO-66 supports, the 15Ni@CUiO-66-NH2 and 20Ni@CUiO-66 catalysts with conversion efficiencies of 87% and 74.5%, respectively, and a methane selectivity of 99% showed the best performance in CO2 methanation at the temperature of 350 °C. The reason for the better performance of xNi@CUiO-66-NH2 catalysts compared to xNi@CUiO-66 catalysts is the presence of basic sites created by nitrogen heteroatoms in the CUiO-66-NH2 support. Also, the results of the tests of CO2 methanation showed that catalysts based on supports with the carbon nanostructure obtained from MOFs showed a higher efficiency compared with the catalysts with the MOF supports. The 15Ni@CUiO-66-NH2 catalyst showed impressive performance in CO methanation with an efficiency of 100% and complete selectivity of methane at 275 °C. Finally, comparing the performance of 15Ni@CUiO-66-NH2 catalyst with other reported catalysts based on carbon supports or based on MOFs, showed the high potential of this catalyst in the process of CO2 and CO methanation.