Molecular Benzene-Heptazine Junction Over Carbon Nitride Frameworks for Dual-Pathway Photosynthesis of Hydrogen...

Tailoring polymeric carbon nitride (CN) to simultaneously broaden its light absorption range and improve charge carrier mobility remains a key challenge for photocatalytic H₂O₂ production. The molecular junction strategy has been proven to be an effective approach to address the aforementioned challenges. In this work, we developed a molecular junction through controlled thermal ring-opening isomerization of benzoguanamine, thereby creating a well-defined C-C-bridged benzene-heptazine molecular junction. Experimental and theoretical studies reveal that: (1) Benzene functionalization extends the π-conjugation, enabling n→π* transitions for broad-spectrum absorption; (2) The donor-acceptor structure enhances self-polarization effects, strengthening the built-in electric field for efficient charge separation; (3) The unique molecular architecture overcomes traditional kinetic limitations, enabling a dual-channel H₂O₂ synthesis mechanism. The optimized catalyst achieves remarkable production rates of 5222 µmol∙g^{- 1}∙h^{- 1} in isopropanol/water and 1587 µmol∙g^-1∙h^-1 in pure water, representing 13.1-fold and 32.4-fold improvements over pristine CN, respectively. This work advances molecular-scale design of photocatalysts and offers new strategies for artificial photosynthesis.