Concentrating substrates within a porphyrin metal-organic cage through supramolecular complexation for efficient photocatalysis

The enzymatic control of reaction rates and selectivity within confined pockets inspires the field of supramolecular catalysis. This study employs a porphyrin metal-organic cage (MOC 1) as a nanoreactor for the photocatalytic oxidation of sulfides. MOC 1 uniquely concentrates substrates within its confined cavity through supramolecular encapsulation of 4–6 sulfides in water, which significantly enhances reactivity and dictates selectivity. Under visible light, MOC 1 catalyses the oxidation of various sulfides to sulfoxides with high conversion and selectivity, effectively suppressing over-oxidation of the product. Mechanistic studies confirm that the reaction proceeds via a superoxide radical (O₂^•–) pathway initiated by photoinduced electron transfer from the cage. This work demonstrates how supramolecular host-guest chemistry can be harnessed to solve challenging reactivity and selectivity problems in photocatalysis, emulating enzymatic function.