The Study On CO₂ Methanation Catalyzed By MOFs Materials

In recent years,the excessive emission of CO2 has become a major threat to both human survival and ecological environment.To cope with the problem,academic circles propose the strategy that as a potential source of Cl,CO2 could be transferred into valuable materials through chemical reactions.Following such idea,it has become a focus of research to find out appropriate reaction and catalyst.Application attempts of metal-organic frameworks(MOFs)in domains like gas adsorption and storage,heterogeneous catalysis have been reported continuously.Some studies have shown that these emerging porous materials have enticing prospects in the field of CO2 conversion due to advantages such as large specific surface area,regular pore structure,and adjustable structure and surface properties.This study took the methanation reaction of CO2 as the starting point,designed and synthesized a highly dispersed MOFs-supported Palladium catalyst,and preliminarily explored the connection between structure and catalytic performance.A couple of results have been obtained:1.Three kinds of MOFs,Cu-BTC,MIL-68(In),and UiO-66,have been prepared as potential CO2 methanation reaction catalyst.The experimental results have shown that there are significant differences in stability among as-synthesized MOFs.Zirconium-based MOFs UiO-66 has both stability under reaction conditions and ideal capacity of CO2 adsorption and activation.2.UiO-66 has been amino-modified in order to enhance the activation of CO2.A series of UiO-66-NH2 samples with different regulators involved in the assembly have been prepared.The crystal structure,pore properties,surface morphology and the capability of CO2 adsorption and activation of the modified MOFs were investigated.The experimental results have shown that the modified product regulated by acetic acid has regular appearance,uniform pore size,and reinforced capability of CO2 adsorption and activation.3.Highly dispersed Palladium nanoparticles were obtained by colloidal method,and supported catalysts Pd@UiO-66 were prepared by incipient impregnation method.The physicochemical structure and properties of the catalysts were systematically studied.The experimental results have shown that the activation of CO2 triggered by MOFs and the dissociation of H2 triggered by supported Pd nanoparticles form a significant synergistic effect:there is a hydrogen overflow between Pd nanoparticles and MOFs,which transports dissociated hydrogen to carriers adsorbing activated CO2 molecules.Thus the hydrogenation process is reinforced.The activity of Pd@UiO-66 with a loading of 6 wt.%was the best,which gives the conversion rate of 56.0%and the selectivity of 97.3%.4.The Pd@UiO-66-NH2 supported catalyst was prepared by the equal volume impregnation method,and the structure and catalytic performance of the material were investigated.The experimental results have shown that CO2 forms carbonate after contact with amino,which reduces the reactivity.The idea of enhancing the catalytic activity by providing Lewis basic sites should be further optimized.