Synthesis of covalent organic frameworks and plasmon-assisted exfoliation for enhanced solar hydrogen production

The development of high-performance covalent organic framework (COF)-based photocatalysts is hindered by their dense layer stacking, lack of intrinsic active sites, and limited light absorption. Herein, we report a "functionalization-assisted exfoliation" strategy that simultaneously addresses these challenges by integrating plasmonic Ni-Co-Mo sulfide nanocavities (NCMS) into a COF matrix. The in situ formation of interfacial CoN and MoN bonds acts as "molecular wedges" to exfoliate the bulk TP-BD covalent organic framework into ultrathin nanosheets (∼1.4 nm) while concurrently establishing covalent "electron highways" for rapid charge transport. The plasmonic NCMS core serves a dual role: it drives the structural transformation and provides dual-pathway plasmonic enhancement via intense photothermal heating (raising the local temperature to ∼99 °C) and hot-carrier generation, which collectively boost light harvesting, optimize reaction kinetics, and elevate the electron reservoir density. The optimized hybrid, denoted MT-3, exhibits exceptional photocatalytic hydrogen evolution rates of 95.6 and 56.4 mmol g^-1 h^-1 under full-spectrum and visible-light irradiation, respectively, with an apparent quantum yield of 25.6% at 420 nm. This performance represents a 956-fold enhancement over the pristine COF and surpasses that of the benchmark Pt-loaded COF by a factor of 18. Comprehensive spectroscopic and microscopic studies elucidate the synergistic interplay of morphological engineering, plasmonic energy conversion, and interfacial electronic coupling. This work provides a versatile design principle for converting inert organic semiconductors into efficient, stable photocatalysts for solar-to-fuel conversion.