Two‐electron oxygen photoreduction to hydrogen peroxide (H2O2) is seriously inhibited by its sluggish charge kinetics. Herein, a polarization engineering strategy is demonstrated by grafting (thio)urea functional groups onto covalent triazine frameworks (CTFs), giving rise to significantly promoted charge separation/transport and obviously enhanced proton transfer. The thiourea‐functionalized CTF (Bpt‐CTF) presents a substantial improvement in the photocatalytic H2O2 production rate to 3268.1 µmol h−1 g−1 with no sacrificial agents or cocatalysts that is over an order of magnitude higher than unfunctionalized CTF (Dc‐CTF), and a remarkable quantum efficiency of 8.6% at 400 nm. Mechanistic studies reveal the photocatalytic performance is attributed to the prominently enhanced two‐electron oxygen reduction reaction by forming endoperoxide at the triazine unit and highly concentrated holes at the thiourea site. The generated O2 from water oxidation is subsequently consumed by the oxygen reduction reaction (ORR), thereby boosting overall reaction kinetics. The findings suggest a powerful functional‐groups‐mediated polarization engineering method for the development of highly efficient metal‐free polymer‐based photocatalysts.

Photocatalytic ammonia synthesis is exciting but quite challenging with a very moderate yield at present. One of the greatest challenges is to develop highly active centers in a photocatalyst for N2 reduction under ambient conditions. Herein, porous carbon‐doped anatase TiOx (C‐TiOx) nanosheets with high‐concentration active sites of Ti3+ are presented, which are produced by layered Ti3SiC2 through a reproducible bottom‐up approach. It is shown that the high‐concentration Ti3+ sites are the major species for the significant increase in N2 photoreduction activity by the C‐TiOx. Such bottom‐up substitutional doping of C into TiO2 is responsible for both visible absorption and generation of Ti3+ concentration. Together with the porous nanosheets morphology and the loading of a Ru/RuO2 nanosized cocatalyst for enhanced charge separation and transfer, the optimal C‐TiOx with a Ti3+/Ti4+ ratio of 72.1% shows a high NH3 production rate of 109.3 µmol g−1 h−1 under visible‐light irradiation and a remarkable apparent quantum efficiency of 1.1% at 400 nm, which is the highest compared to all TiO2‐based photocatalysts at present.

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Designing a highly active and stable catalyst for NaBH4 hydrolysis is a key step towards overcoming the challenges of hydrogen storage.

A synergistic oxygen substitution and heterostructure construction strategy was developed to synthesize oxygenated-triazine-heptazine-conjugated polymer nanoribbons for photocatalytic water splitting.