Organic semiconductors offer a tunable platform for photocatalysis, yet the more difficult exciton dissociation, compared to that in inorganic semiconductors, lowers their photocatalytic activities. In this work, we report that the charge carrier lifetime is dramatically prolonged by incorporating a suitable donor-acceptor (β-ketene-cyano) pair into a covalent organic framework nanosheet. These nanosheets show an apparent quantum efficiency up to 82.6% at 450 nm using platinum as co-catalyst for photocatalytic H2 evolution. Charge carrier kinetic analysis and femtosecond transient absorption spectroscopy characterizations verify that these modified covalent organic framework nanosheets have intrinsically lower exciton binding energies and longer-lived charge carriers than the corresponding nanosheets without the donor-acceptor unit. This work provides a model for gaining insight into the nature of short-lived active species in polymeric organic photocatalysts.

Organic–inorganic hybrid perovskites have demonstrated great potential in solar cell fabrication due to excellent optoelectronic properties. However, their success in solar cells has been hardly translated to producing solar fuels because of instability issues and serious charge recombination at the nanoscale domain. Herein, we show for the first time that organic–inorganic hybrid perovskite methylammonium lead bromide (MAPbBr3) nanocrystals can be stabilized in aqueous HBr solution and achieve photocatalytic H2 production reaction under visible light. More impressively, by hybridizing MAPbBr3 with Pt/Ta2O5 and poly­(3,4-ethylenedioxythiophene) polystyrenesulfonate (PEDOT:PSS) nanoparticles as electron- and hole-transporting motifs, respectively, drastically enhanced charge transportation on MAPbBr3 and improved catalysis were achieved. As a consequence, the rate of photocatalytic hydrogen evolution on pristine MAPbBr3 was increased by ca. 52 times by introducing dual nanoscale charge-transporting highways, achieving an apparent quantum efficiency of ca. 16.4% for H2 evolution at 420 nm.