Molecular Heterostructures of Covalent Triazine Frameworks for Enhanced Photocatalytic Hydrogen Production

Conjugated polymers have emerged as promising candidates for photocatalytic H₂ production owing to their structural designability and functional diversity. However, the fast recombination of photoexcited electrons and holes limits their H₂ production rates. We have now designed molecular heterostructures of covalent triazine frameworks to facilitate charge-carrier separation and promote photocatalytic H₂ production. Benzothiadiazole and thiophene moieties were selectively incorporated into the covalent triazine frameworks as electron-withdrawing and electron-donating units, respectively, by a sequential polymerization strategy. The resulting hybrids exhibited much improved charge-carrier-separation efficiency as evidenced by photophysical and electrochemical characterization. An H₂ evolution rate of 6.6 mmol g^-1 h^-1 was measured for the optimal sample under visible-light irradiation (λ>420 nm), which is far superior to that of most reported conjugated-polymer photocatalysts.