Donor-Acceptor-Type Heptazine-Based Polymer Networks for Photocatalytic Hydrogen Evolution

A heptazine-based polymer network (HMP-3) with a donor-acceptor (D-A) structure was prepared and tested as catalyst for photocatalytic hydrogen evolution from water. Compared to other heptazine-based materials, which are typically prepared at high temperatures and have recently received much interest as metal-free photocatalysts, the low-temperature protocol applied here allows the defined introduction of organic functional groups within the polymer backbone. The structure of HMP-3 contains alternating heptazine and benzothiadiazole moieties as electron acceptors connected by aminobenzene bridges as electron donors. The resulting material leads to enhanced hydrogen evolution compared to graphitic carbon nitride materials prepared at high temperatures (> 500 degrees C) most probably because of the stabilization of photogenerated charge carriers in the D-A structure.