Unsaturated iron ion based coordination polymer for highly efficient photocatalytic hydrogen evolution with simultaneous real wastewater degradation: Mechanistic insight into multifunctional Fe-N sites

Simultaneous photocatalytic reactions of H2 evolution and real wastewater degradation have drawn much attention to practical energy and environmental applications. While these applications of photocatalyst often suffer from the high charge-carrier recombination and poor efficiency in reactants activation, resulting in unsatisfactory photocatalytic activity or need expensive platinum co-catalyst. Here, the unsaturated iron ion based coordination polymer (FeTMT) with weak Fe-N sites has been fabricated by a facile wet-chemical method. It exhibits outstanding photocatalytic performance for the simultaneous production of H2 (1272 μmol g-1 h-1) and degradation of real wastewater from brewing liquor (degradation efficiency is 60%) without using any cocatalyst, which is larger than that reported system. The density functional theory (DFT) calculations revealed that the unsaturated Fe-N bridge could transfer the electrons from C3N3S3 rings to Fe3+, boosting the separation and transportation efficiency of charge carriers. On the other hand, the N functional group close to the metal centers in FeTMT could regarded as a proton relay to enhance the surface of hydrophily. Further in-situ test demonstrated that unsaturated Fe sites could adsorb H+ to form H-Fe-H bond, while Fe-N sites serve as the catalytic active centers in FeTMT. This finding opens an avenue to construct a novel coordination polymer and deep understanding for the practical industrial photocatalysis application