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In this study, we have demonstrated photocatalytic H2 evolution by water splitting coupled with biomass derived 5-(hydroxymethyl) furfural (HMF) oxidation to a more valued platform chemical, 2,5-diformylfuran (DFF), under visible light using porous carbon nitride (SGCN) for the first time. Simultaneously, a H2 production rate of 12 μmol h−1 m−2 was obtained with a DFF yield of 13.8% with >99% selectivity after 6 h under visible light. The selectivity of DFF was maintained >99% even after longer runs (48 h) with an improved DFF yield of 38.4% and H2 production rate of 36 μmol h−1 m−2. In addition, a H2 production rate of 6.2 μmol h−1 m−2 with 0.15 light-to-fuel efficiency (LFE) and DFF (7.2% yield) were obtained under natural sunlight after 6 h. Thus, this study describes an effective way to utilize both photogenerated electrons and holes for simultaneous H2 production by water splitting and biomass derived HMF oxidation to DFF, respectively, under natural sunlight.

Metal-free organic polymer photocatalysts have attracted dramatic attention in the field of visible light-induced hydrogen evolution reaction (HER). Herein, we showed a polymeric O-linked heptazine polymer (OLHP) decorated with S, N co-doped graphene quantum dots (S,N-GQDs) as a photosensitizer to generate hydrogen upon quantum dot sensitization. Both of these heptazine-based systems show effective photosensitization with strong π–π interactions and enhanced photocatalytic H2 generation (24 times) as metal-free systems. Electrochemical impedance and optical measurements show effective charge transfer kinetics with decreased charge recombination, which is responsible for the enhanced photocatalytic activity. As a result, a significant high apparent quantum yield (AQY) with highest value of 10.2% was obtained for our photocatalyst OLHP/S,N-GQD10.