In Situ Growth of Metal-Organic Layer on Polyoxometalate-etching Cu2O to Boost CO2 Reduction with High Stability

Low-cost Cu2O with a suitable band gap holds great potential for solar utilization. However severe photocorrosion and weak CO2 capture capability have significantly hindered their application in artificial photosynthesis. Herein, polyoxometalate (POM)-etching and in situ growth of metal-organic framework (MOF) can simultaneously incorporate electron-sponge and HKUST protective layer into Cu2O. The resulting ternary composites Cu2O@POM@HKUST-n (POM = PMo12O40 and PW12O40) with dual hetero-interfaces can efficiently convert CO2 to HCOOH with 5226 µmol g-1 yield, over 5 and 55 times higher than that of Cu2O (1010 µmol g-1) and Cu2O@HKUST (95.02 µmol g-1). In situ XPS and DFT studies reveal that Cu mainly existed in the form of Cu2O and Cu-MOF, while a unique Cux+ (1< x ≤2) surface layer formed upon the Cu2O matrix surrounding POMs for CO2 absorption and activation. Systematic investigations demonstrate that the electron-sponge can efficiently capture electrons from excited Cu2O to promote the generation of a Cux+ surface layer, while the closely surface-coating metal-organic layer can act as protective layer and CO2 adsorbent. This dual function concurrently contributes to promote photocatalysis and prevent Cu2O degradation. Remarkably, the ternary composites exhibit much enhanced photochemical stability and can be used for over 60 h without noticeable activity loss.