Bridging ZnTPP with PDI via Phosphate Ligands for Enhanced Charge Transfer in CO ₂ -to-CH ₄ Photoreduction

The photocatalytic reduction of CO2 (CO2RR) to CH4 provides a viable strategy for simultaneously addressing global energy demands and climate change. However, the prevalent recombination of photogenerated carriers still impedes efficient charge separation and migration, resulting in detrimental effects on both the selectivity and the yield. Herein, a P-PDI/ZnTPP Z-scheme heterojunction is constructed via self-assembly, where the P–O–Zn bridge serves as an efficient internal electron transfer channel, which enables the rapid migration of photoelectrons from P-PDI to ZnTPP. Spectroscopic investigations reveal that the P–O–Zn bridge further facilitates the separation of photogenerated charges and reduces the recombination of holes and electrons in PDI and ZnTPP. Remarkably, the P-PDI/ZnTPP heterojunction achieves CH4 production with a selectivity of 96% and a rate of 201 μmol·h–1·g–1, exceeding those of P-PDI alone and ZnTPP. The introduction of a “bridge” to construct an electron transfer channel offers an approach for fabricating molecular photocatalysts for the reduction of CO2 into valuable products.