Effect of Pyrene-Benzothiadiazole Linkage Sites on Photocatalytic Hydrogen Evolution

The design and synthesis of organic polymers for photocatalytic hydrogen evolution have attracted recent attention. However, the corresponding work on the synthesis methods and optimal synthesis sites of organic polymers are not complete. This paper was to synthesize five organic polymer photocatalysts via a Suzuki cross-coupling polymerization reaction. The effect of linking position content on the photocatalytic H₂-evolution and photoelectrochemical performances of organic polymer semiconductors was investigated. The results show that the increase of 1,6-linkage pattern severely affects the photocatalytic hydrogen evolution effect. A 1,6-linked pyrene benzothiadiazole polymer (L16-PyBT) has a photocatalytic hydrogen evolution rate of 6.81 mmol/(h·g) under visible-light irradiation, which is greater than that of L2 (i.e., 2.80 mmol/(h·g) and L27-PyBT (i.e., 0.34 mmol/(h·g). The increased photocatalysis is since 1,6-linkage has a stronger π-π stacking, and better absorption/wettability. The evolution of this connection mode provides an important idea for the synthesis and design of organic polymers in the future.