Zn-Co bimetallic catalysts before and after calcination: Research on their different properties for cycloaddition and Friedel-Crafts acylation reactions

A series of bimetallic Zn-Co catalysts before and after calcination were prepared by simple MOFs template methods. The effects of calcination on their structures were investigated by XRD, FT-IR, TPD, XPS and EPR characterization methods, and their catalytic performances were compared in the cycloaddition reactions of CO2 and propylene oxide and acylation reactions of anisole and acetyl chloride, respectively. The results show that uncalcined ZnCo2-MOFs catalyst has excellent catalytic performance for cycloaddition reaction due to the presence of acid-base synergism, whereas the strong acidity of calcined ZnCo2OX catalyst is very favorable for acylation reaction. This is due to the fact that calcination changes the structure of ZnCo2-MOFs catalyst, causes charge migration on the surface and results in the conversion of lattice oxygen to oxygen vacancies, which brings a large difference in the acidity and basicity of catalysts.