Visible light-mediated intermolecular crossed [2+2] cycloadditions using a MOF-supported copper triplet photosensitizer

The photochemical [2+2] cycloaddition of styrenes provides a frequently used route for the synthesis of multi-substituted cyclobutanes. Despite the extensive studies in noble-metal and organo-photocatalysis, developing sustainable cycloaddition methods with copper photosensitizers is still in its infancy, largely owing to their low reactivity and photostability. Here we show that the introduction of a binap-ligated heteroleptic copper(I) complex to the linker of a microporous zirconium-based metal−organic framework produces a highly stable and reusable heterogeneous photocatalyst with an extended excited-state lifetime. Under visible light irradiation, this robust copper triplet photosensitizer efficiently promotes multiple intermolecular crossed [2+2] cycloadditions, including an underdeveloped cycloaddition reaction of simple styrenes with electron-deficient alkenes. Our findings suggest that metal–organic framework-based heterogenization strategies have the potential to advance copper photocatalysis and foster a variety of visible light-mediated energy-transfer processes.