Mass transfer-based heterogeneous photocatalysis: Hollow porous polystyrene nanospheres as a platform for efficient energy transport of iridium (III) complex

Abstract

Heterogeneous photocatalysis of iridium (III) complexes faces two major bottle-necks: limited mass/energy transfer and tedious immobilization. In this work, fac-Ir(ppy)3 is directly anchored to hollow mesoporous polystyrene nanospheres (HMPNs) via one-pot F-C alkylation, achieving the covalent immobilization of fac-Ir(ppy)3 at a low-cost. The thin shell, pores, hollow interior, and swelling property of HMPNs enable reactants to quickly access to fac-Ir(ppy)3, effectively avoiding energy loss in energy transport from excited fac-Ir(ppy)3* to reactants. The mass transfer of reactants and optical properties of fac-Ir(ppy)3 such as quantum yield, luminescent lifetime and band gap energy closely depend on the cross-linking degree of polystyrene. The anchored fac-Ir(ppy)3 exhibits comparable catalytic activity to homogeneous fac-Ir(ppy)3 in heterogeneous [2 + 2] photodimerization of olefins with a good reusability without a significant decrease in yields over ten recycles. This work develops a strategy for fabricating efficient heterogeneous photocatalysts using available non-conjugated polymer as support based on the concept of fast mass transfer of reactants.