Selective Preference of Pt Atoms on Covalent Triazine Frameworks in CO₂ Photoreduction: Insight into Energy Transfer Mechanisms

Metal-loaded COF-based photocatalysts facilitate the conversion of CO2 and H2O into storable fuels through a photosynthesis-like mechanism, providing an efficient approach to addressing energy challenges. However, the fundamental principles governing internal energy transfer and reaction pathways remain insufficiently understood, posing significant barriers to achieving photocatalytic reactions with high selectivity and specificity. This study explores the heavy-atom effect of Pt on exciton-mediated energy transfer by synthesizing single-atom dispersed PtSA-CTF and nanoparticle-aggregated PtNP-CTF on defective CTF substrates, thereby revealing the selective preferences of Pt species and their impact on reaction pathways. By combining exciton behavior characterization (fs-TA), photoreaction pathway validation (13CO2 isotope labeling) with excited-state theoretical calculations (TD-DFT), it was demonstrated that excitons in PtSA-CTF undergo resonance energy transfer to the CO2 intermediate during the relaxation process from the triplet state to the ground state. The *CO2 intermediate then reacts with the sequentially generated electrons and protons, resulting in high performance with a CO yield of 6.778 mmol·g–1·h–1, 98.2% selectivity, and a TOF of 1102.68 h–1. This work provides valuable insights into the photophysical properties induced by excitonic and heavy-atom effects, offering guidance for improving the efficiency and selectivity of photocatalytic reactions and the rational design of advanced photocatalysts.