Ultrathin phosphate-modulated zinc phthalocyanine/perylenete diimide supermolecule Z-scheme heterojunctions as efficiently wide visible-light photocatalysts for CO2 conversion

Abstract Ultrathin phosphate-modulated zinc phthalocyanine/perylene diimide supermolecule (ZnPc/P-PDI) heterojunctions have been successfully constructed as efficient wide visible-light photocatalysts for converting CO2. The key to realize this construction is to establish a facile phosphate-induced assembly of ZnPc on PDI with the improved dispersion by strengthening H-bonding connection. The amount-optimized ZnPc/P-PDI heterojunction shows an exceptional photoactivity by ~30-fold enhancement compared with PDI. Based on the time-resolved surface photovoltage responses, low-temperature electron paramagnetic resonance and in-situ diffuse reflectance infrared Fourier transform spectroscopy spectra, etc., it is confirmed that the excellent photocatalytic performance mainly depends on the greatly-enhanced charge transfer and separation in the fabricated closely-contacted Z-scheme heterojunction with the increased amount of ZnPc, along with the formed negative field on resulting PDI by the modified phosphate anions for trapping photogenerated holes. Moreover, it is proved that the excited electrons of ZnPc could continuously transfer from the ligand to the central Zn2+ with good catalytic function for CO2 reduction.