Surface-Grafted Single-Atomic Pt-N_x Complex with a Precisely Regulating Coordination Sphere for Efficient Electron...

Based on the electron-withdrawing effect of the Pt(bpy)Cl₂ molecule, a simple post-modification amide reaction was firstly used to graft it onto the surface of NH₂-MIL-125, which performed as a highly efficient electron acceptor that induced the conversion of the photoinduced charge migration pathway from internal BDC→TiO_x migration to external BDC→PtN_x migration, significantly improving the efficiency of photoinduced electron transfer and separation. Furthermore, precisely regulating over the first coordination sphere of Pt single atoms was achieved using further post-modification with additional bipyridine to investigate the effect of Pt-N_x coordination numbers on reaction activity. The as-synthesized NML-PtN₂ exhibited superior photocatalytic hydrogen evolution activity of 7.608 mmol g^-1 h^-1, a remarkable improvement of 225 and 2.26 times compared to pristine NH₂-MIL-125 and NML-PtN₄, respectively. In addition, the superior apparent quantum yield of 4.01 % (390 nm) and turnover frequency of 190.3 h^-1 (0.78 wt % Pt SA; 129 times compared to Pt nanoparticles/NML) revealed the high solar utilization efficiency and hydrogen evolution activity of the material. And macroscopic color changes caused by the transition of carrier migration paths was first observed. It holds profound significance for the design of MOF-Molecule catalysts with efficient charge carrier separation and precise regulation of single-atom coordination sphere.