Covalent triazine frameworks modified by ultrafine Pt nanoparticles for efficient photocatalytic hydrogen production

Pt nanoparticles (PtNPs) as active species have always been considered as one of the best semiconductor materials for photocatalytic hydrogen production. In this study, a Schottky heterojunction has been successfully constructed by evenly loading ultrafine PtNPs onto a triazine-based covalent organic frameworks (COFs). This strategy maintained the high activity of these ultra-small PtNPs while maximizing the utilization of the Pt active sites. The fabricated PtNPs@covalent triazine-based framework-1 (CTF-1) composite accomplished a significantly high rate of hydrogen evolution (20.0 mmol·g⁻¹·h⁻¹, apparent quantum efficiency (AQE) = 7.6%, at λ = 450 nm) with 0.40 wt.% Pt loading, giving rise to a 44-fold-increase in the efficiency of the photocatalytic hydrogen production compared to the pristine CTF-1. Theoretical calculations revealed that the strong electron transfer (Q(Pt) = −0.726 q_e, in the analysis of Bader charge, Q(Pt) is the charge quantity transferred from Pt cluster to CTF-1, and q_e is the unit of charge transfer quantity) between PtNPs and CTF-1 triggers a strong interaction, which makes PtNPs being firmly attached to the structure of CTF-1, thereby enabling high stability and excellent hydrogen production efficiency. Importantly, the hydrogen binding free energy (ΔG_H*) of PtNPs@CTF-1 is much lower than that of the unmodified CTF-1, leading to a much lower intermediate state and hence a significant improvement in photocatalytic performance. The overall findings of this work provide a new platform to incorporate metallic NPs into COFs for the design and fabrication of highly efficient photocatalysts.