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.