Modulating interfacial charges in CTF-based metal-insulator-semiconductor promotes selective CO2 reduction to CH4

A metal-insulator-semiconductor (MIS) ternary photo-system was intricately crafted through precise amalgamation polyvinylpyrrolidone (PVP)-capped metal Cu with typical covalent triazine framework CTF-1 via electrostatic self-assembly. The 2 % Cu-PVP-CTF exhibited an impressive CH4 yield of 80.7 mu mol & sdot;g � 1 & sdot;h- 1 with selectivity of 96.8 % under visible light, representing a 2.3-fold and 112-fold improvement over Schottky-type Cu-CTF and pristine CTF-1, respectively. In-situ XPS and VASP-diff calculations unfolded that the ultrathin PVP insulating layer significantly expedited interfacial charges tunneling, corroborated by smaller lifetime tau 2 determined via femtosecond transient absorption spectroscopy. The intermediates of paramount importance in CO2 reduction like *COOH and *HCHO were meticulously monitored by in-situ Fourier infrared spectroscopy. DFT calculations elucidated that Cu-PVP-CTF was notably more adept at facillitating the rate-determining step (*COOH -> *CO) to produce CH4 than Cu-CTF. This work tamps the groundwork for conceptional roadmap in designing novel MIS photo-system for CO2 conversion.