Charge separation enhanced tunable D-A integrated ionic porous organic polymers for the efficient photosynthesis of H2O2 from air and (Sea)water.

Solar-driven green photocatalytic H2O2 production is a potent breakthrough technology, especially with advanced porous materials. However, the design of porous-material-based superior photocatalysts with high inherent charge separation and ORR selectivity is very challenging. In this direction, we present a rationally designed series of halide-anion-tunable cationic protonated imidazoline-core-bearing porous polymers (IPM-402Xs, X= -F, -Cl, or -Br), featuring spatially isolated redox centers with ionicity-enhanced intra-system donor-acceptor electronic properties. These polymers enable highly efficient photosynthesis of H2O2, with a production rate of 1922 µmol h-1 g-1, an unprecedented apparent quantum yield (%AQY) of 18.94, and a solar-to-chemical energy conversion (%SCC) of 1.02 for IPM-402F in O2-saturated H2O. IPM-402Xs showed excellent H2O2 photoproduction from seawater in sunlight and air, achieving 293 µmol h-1 g-1 with IPM-402F. Excited-state relaxation by anion alteration was investigated by TA analysis, backed by theoretical calculations, to understand the photocatalytic efficiency and underlying reaction mechanism of the direct 2e- ORR. This study reveals the broad potential of unexplored multifunctional tunable ionic frameworks for sustainable, green, and highly efficient H2O2 photoproduction.