Porous polyselenoviologen with long-lived charge separated states and highly cyclic stability for heterogeneous photocatalytic reaction and hydrogen production

A highly stable heterogeneous photocatalyst, porous polyselenoviologen (POP-SeV²⁺), was successfully synthesized via S_N2 reaction. Compared to the monomer, POP-SeV²⁺ exhibited strong visible-light absorption, enhanced electron acceptor property, and prolonged lifetime of radical cations. Simultaneously, the femtosecond transient absorption (fs-TA) illustrated that the formation of tetrahedral multi-cationic structure is conducive to the rapid generation of molecular excited states and extending the duration of charge-separated states. Due to its remarkable characteristics, the POP-SeV²⁺ was employed as a photocatalyst for visible-light-induced cross-dehydrogenative coupling (CDC) reactions with a highly efficient yield (82 %). Additionally, its utilization was further extended to the hydrogen generation, demonstrating remarkable outcomes such as a high rate of H₂ generation (300 μmol·h⁻¹·g⁻¹), and an apparent quantum yield (0.13 %). Notably, POP-SeV²⁺ displayed great stability and reusability in the photocatalytic process, which can distinguish it from those soluble SeV²⁺-based photocatalysts. The catalytic efficiency of POP-SeV²⁺ remained virtually unaffected even after undergoing several recycling cycles, which not only achieved the complete heterogeneous photocatalysis of SeV²⁺-based systems for the first time but also provided a new strategy to improve the application effect of viologen derivatives in solar energy conversion and utilization.