Donor–acceptor covalent organic frameworks-confined ultrafine bimetallic Pt-based nanoclusters for enhanced photocatalytic H2 generation

Photocatalytic hydrogen generation from hydrogen storage media is an effective and promising approach for the green hydrogen industry as well as for achieving carbon neutrality goals. However, the lower photocatalytic efficiency due to the limited light trapping capacity, low electron transfer rate, and severe aggregation of nanoparticles caused by high surface energy seriously restricts their practical application. Herein, we constructed a series of donor–acceptor (D–A) type covalent organic frameworks to confine ultrafine bimetallic Pt-based nanoclusters for photocatalytic hydrogen generation from ammonia borane (AB) hydrolysis. Under visible light irradiation at 20 °C, PtCo2@covalent organic framework (COF) showed the highest photocatalytic activity with a turnover frequency (TOF) of 486 min−1. Experiments and density functional theory (DFT) calculations reveal that the high catalytic activity is mainly attributed to the strong electronic interactions between D–A type COF and ultrafine PtCo2 nanoclusters. Specifically, the D–A type COF can significantly enhance the light-trapping ability by fine-tuning the electron-acceptor type in the framework, and accelerate the photogenerated electron transfer from D–A type COF to PtCo2 nanocluster, which promotes the adsorption and activation of H2O and AB molecules and accelerates hydrogen release. Furthermore, PtCo2@COF also exhibited ultra-high durability due to the significantly enhanced resistance to nanocluster aggregation caused by the nanopore confinement effect of D–A type COF. We believe that this work will provide a theoretical guide for the rational design of efficient D–A COF-based catalysts for photocatalysis.