Insights into the plasmonic "hot spots" and efficient hot electron injection induced by Ag nanoparticles in a covalent organic framework for photocatalytic H₂ evolution

The effective utilization of the local surface plasmon resonance (LSPR) effect of metal nanoparticles to improve optical absorption capacity and inject hot electrons into photocatalysts opens up new directions and ideas to solve the problem of solar energy utilization efficiency of photocatalysts. In this study, we created an in situ technique for preparing plasmon Ag nanoparticles (NPs) decorated with a covalent organic framework (COF), named Ag/TpPa-1-COF. The LSPR effect of Ag NPs results in an outstanding rate of H-2 production that is 801.4 mu mol g(-1) h(-1) for the 3% Ag/TpPa-1 photocatalyst, which is almost 4 times as effective as that of the unmodified TpPa-1-COF. Moreover, finite-difference time-domain (FDTD) simulation results reveal that the strongest electric field intensity is presented when the catalyst is excited at lambda = 465 nm. Furthermore, plasmonic "hot spots" induced by the interfacial electric field enhancement factor distribution of Ag/TpPa-1 were simulated in detail by adjusting the number, particle size, and gap distance of Ag NPs. Additionally, density functional theory (DFT) calculations show that electron transfer from Ag NPs to TpPa-1 occurs at the Ag/TpPa-1 interface, and N sites in Ag/TpPa-1 exhibit low Gibbs free energy (Delta G(H*)) for enhanced photocatalytic H-2 evolution. Overall, this research provides new insights into the plasmonic "hot spot" region that performs effectively for hydrogen evolution.