Titanium metal–organic frameworks for photocatalytic CO2 conversion through a cycloaddition reaction†

The elevated levels of CO₂ in the atmosphere have been a major concern for environmental scientists. Capturing CO₂ gas and its subsequent conversion to useful organic compounds is one of the avenues that have been extensively studied in the last decade. The photocatalytic cycloaddition of CO₂ is a promising approach for effective CO₂ capture and the production of value-added chemicals such as cyclic carbonates. MOF-901, a titanium-based metal–organic framework with hexagonal layers and imine linkages, was successfully oxidized in this study to MOF-997, incorporating amide linkages using Oxone. Both MOFs displayed remarkable photocatalytic activity in CO₂ cycloaddition under mild conditions, including moderate temperatures and visible light exposure. Particularly noteworthy is MOF-997, exhibiting superior performance with donor–acceptor active sites, achieving a 99.9% yield in catalyzing CO₂ conversion from styrene epoxide to styrene carbonate under solvent conditions.