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

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 pi-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 mu mol 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.