A Metal–Organic Framework Catalyst Facilitating Transformation of CO2 and Styrene Oxide into Styrene Carbonate and Friedel–Crafts Alkylation

Abstract

Carbon dioxide (CO₂) is a major greenhouse gas that poses serious environmental and health risks. Converting CO₂ into valuable chemicals or fuels offers a sustainable solution to reducing fossil fuel dependence. Metal–organic frameworks (MOFs) are efficient catalysts in CO₂ cycloaddition due to their porosity, nitrogen-rich ligands, and dual Lewis acid–base active sites, enhancing catalytic efficiency and enabling efficient CO₂ utilization. Therefore, we designed a stable microporous MOF with a nitrogen-rich ligand. This activated MOF (1′) demonstrates exceptional stability and high surface area, which is effective for the adsorption of CO₂ molecules into its pore. The use of 1′ efficiently converts CO₂ and epoxides into cyclic carbonates under moderate conditions, exhibiting an excellent catalytic performance. Catalyst 1′ showed outstanding catalytic activity even after a fourth cycle with a minimal loss of its efficiency. Furthermore, the catalytic performance of 1′ was also tested in the Friedel–Crafts alkylation of indole with β-nitrostyrene in toluene using 1′ as a catalyst. The solid retained its activity over four cycles, with unchanged integrity and morphology. Additionally, wide substrate scopes were achieved for both of the catalytic reactions under optimized conditions. These findings highlight the potential of nitrogen-rich MOFs as sustainable catalysts for CO₂ conversion and valuable chemical synthesis.