Towards High CO₂ Conversions Using Cu/Zn Catalysts Supported on Aluminum Fumarate Metal-Organic Framework for Methanol Synthesis

Green methanol is a viable alternative for the storage of hydrogen and may be produced from captured anthropogenic sources of carbon dioxide. The latter was hydrogenated over Cu-ZnO catalysts supported on an aluminum fumarate metal-organic framework (AlFum MOF). The catalysts, prepared via slurry phase impregnation, were assessed for thermocatalytic hydrogenation of CO₂ to methanol. PXRD, FTIR, and S_BET exhibited a decrease in crystallinity of the AlFum MOF support after impregnation with Cu-Zn active sites. SEM, SEM-EDS, and TEM revealed that the morphology of the support is preserved after metal loading, where H₂-TPR confirmed the presence of active sites for hydrogen uptake. The catalysts exhibited good activity, with a doubling in Cu and Zn loading over the AlFum MOF, resulting in a 4-fold increase in CO₂ conversions from 10.8% to 45.6% and an increase in methanol productivity from 34.4 to 56.5 g_MeOH/Kg_cat/h. The catalysts exhibited comparatively high CO selectivity and high yields of H₂O, thereby favoring the reverse water-gas shift reaction. The selectivity of the catalysts towards methanol was found to be 12.9% and 6.9%. The performance of the catalyst supported on AlFum MOF further highlights the potential use of MOFs as supports in the heterogeneous thermocatalytic conversion of CO₂ to value-added products.