Construction of novel intramolecular g-C₃N₄ based D-A₁-π-A₂ conjugated copolymers with promoted charge separation for efficient photocatalytic hydrogen evolution

In the strategies of modifying g-C₃N₄ by changing its electron transport structure, it has been demonstrated that constructing donor-acceptor (D-A) or D-π-A g–C₃N₄–based conjugated copolymers can obviously accelerate the separation of charge carriers. Inspired by their advantages, a novel g–C₃N₄–based D-A₁-π-A₂ type polymer was designed and synthesized via the thermal copolymerization of urea and PA-PM (the product of the amidation reaction between PA and PM). As a result, the prepared CN-PA-PM photocatalysts with D-A₁-π-A₂ structure not only improve visible-light response, but also promote the separation of charge carriers, thereby achieving superior photocatalytic hydrogen evolution activity. The optimized CN-PA-PM-13 polymer has the best hydrogen evolution efficiency of 17.79 mmol g⁻¹ h⁻¹ under visible light (λ > 420 nm), which is 33.7 times that of pure g-C₃N₄. This work presents a new design concept for g–C₃N₄–based polymer photocatalysts with high optical absorption capability and effective carrier separation ability.