In situ self-assembly of zirconium metal–organic frameworks onto ultrathin carbon nitride for enhanced visible light-driven conversion of CO2 to CO

Abstract

A series of Zr-porphyrin metal–organic framework (Zr-PMOF)/ultrathin g-C₃N₄ (UCN) (ZPUCN) heterostructure photocatalysts, as stable and efficient catalysts for the photoreduction of CO₂, have been fabricated via a facile in situ hydrothermal self-assembly method. An interfacial interaction is formed due to hollow Zr-PMOF nanotubes being surrounded by 3D ultrathin g-C₃N₄ (UCN) and benefiting from the ultrathin and conjugated π-structure of UCN, the unsaturated metal atoms and organic ligands of Zr-PMOFs can covalently link to organic g-C₃N₄. The interaction provides a platform for UCN as a conductor to transfer e⁻ or as a donor to transfer e⁻ to Zr–O cluster active sites to catalyze CO₂, substantially achieving the spatial separation of charge carriers and suppressing the photogenerated electron–hole (e⁻–h⁺) pair recombination rate. Benefitting from the cooperative effects of the well-designed nanostructure and chemical grafting, in the absence of triethanolamine, cocatalysts and photosensitizers, the optimized ZPUCN hybrid not only exhibits a better CO evolution yield (5.05 μmol g⁻¹ h⁻¹), which is 2.2 times and 3.2 times higher than those of pure Zr-PMOFs and UCN, respectively, but also displays excellent stability after 96 h photocatalysis. Information about the mechanism is also elucidated from selected characterizations.