Quasi-homogeneous catalytic platform of efficient enantioselective dual photocatalysis: Brush-supported Ir complexes/chiral phosphoric acids for the economic synthesis of optically active molecules

Current heterogeneous enantioselective photocatalysis of dual catalysts faces the key limiting factors including multi-step immobilization of catalysts, insufficient electron/energy transfer and limited mass transfer of reactants. In this paper, the direct immobilization of dual catalysts without molecular modification, including three catalyst combinations of Ir complexes and chiral phosphoric acids (CPAs), into SiO₂-grafted linear poly(4-vinylbenzyl chloride) (PVBC) brushes is developed via one-pot Friedel-Crafts alkylation. The PVBC brushes-supported dual catalysts possess improved optical properties including light-harvesting, optical bandgap energy, emission lifetime, and quantum yield in comparison to pore-anchored dual catalysts. Meanwhile, owing to the open-ended structure and good dispersibility of PVBC brushes in organic solvents, the energy/electron transfer and mass transfer of reactants to catalytic sites are improved due to quasi-homogeneous catalysis, which enables the anchored dual catalysts to achieve comparable catalytic performances to homogeneous counterparts in enantioselective photocatalysis. Overall, the quasi-homogeneous enantioselective photocatalysis of dual catalysts provides an effective platform for the low-cost synthesis of chiral molecules in green manner.