Photocatalytic nitrogen fixation of metal-organic frameworks (MOFs) excited by ultraviolet light: Insights into the nitrogen fixation mechanism of missing metal cluster or linker defects

The vacancies of semiconductors have proven to be effective active sites for photocatalytic nitrogen fixation, but what about the role of defects in MOF materials? Herein, we report the first UiO-66 with photo-excited cluster defects and linker defects for photocatalytic nitrogen fixation. It was determined through the post-synthetic ligand exchange (PSE) process that the linker defects, rather than cluster defects, can greatly improve the performance, which is due to linker defects forming unsaturated metal nodes such as the vacancy in a semiconductor. Specifically, for photo-activated UiO-66, the NH4+ production rate was 196 and 68 μmol g-1 h-1 in air atmosphere under ultraviolet-visible (UV-Vis) and visible light, respectively. This report provides a new effective strategy to design efficient nitrogen fixation photocatalysts.