3D Fe-MOF embedded into 2D thin layer carbon nitride to construct 3D/2D S-scheme heterojunction for enhanced photoreduction of CO2

Regulating charge transfer to achieve specific transfer path can improve electron utilization and complete efficient photoreduction of CO2. Here, we fabricated a S-scheme heterojunction of CN/Fe-MOF by an in-situ assembly strategy. The S-scheme charge transfer mechanism was confirmed by band structure, electron spin resonance (ESR) and work function (Φ) analysis. On the one hand, the response of Fe-MOF in the visible region improved the utilization of light energy, thus increasing the ability of CN/Fe-MOF to generate charge carriers. On the other hand, CN, as the active site, not only had strong adsorption capacity for CO2, but also retained photogenerated electrons with high reduction capacity because of S-scheme charge transfer mechanism. Hence, in the absence of any sacrificial agent and cocatalyst, the optimized 50CN/Fe-MOF obtained the highest CO yield (19.17 μmol g−1) under UV-Vis irradiation, which was almost 10 times higher than that of CN. In situ Fourier transform infrared spectra not only revealed that the photoreduction of CO2 occurred at the CN, but also demonstrated that the S-scheme charge transfer mechanism enabled 50CN/Fe-MOF to have a stronger ability to generate HCOO− than CN.