Synthesis and Photocatalytic Hydrogen Evolution Study of Triazine-Based Conjugated Microporous Polymers

Photocatalytic water splitting to produce hydrogen is one of the effective ways to achieve solar energy utilization, in which the key point is to develop efficient and cheap photocatalysts. Conjugated microporous polymers (CMPs), allowing the fine synthetic control over their chemical structures and electronic properties, have become a new type of photocatalysts due to their diverse synthetic modularity. In order to investigate the effects of molecular structures on the photocatalytic performance of CMPs, four triazine-based conjugated microporous polymers (TCMPs) were designed and synthesized by Suzuki coupling reaction in this work, among which, TTCMP1 and TTCMP2 contain thiophene units, and TFCMP1 and TFCMP2 possess fluorene units. These TCMPs have high specific surface areas and appropriate optical band gaps. Through optical analysis of these TCMPs, it is found that the structural change of functional units and the length of linkers can tune the energy band gap, thereby influencing the hydrogen production performance of the polymers. Results show that TFCMPs containing fluorene units show better photocatalytic hydrogen production performance. And TFCMP2 with longer linking units shows the highest hydrogen release rate of 244 μmol/(h·g) under visible light (λ ≥ 420 nm). This work provides a promising strategy for exploring the relationship between the structure and performance of CMPs for photocatalytic hydrogen evolution.