Toward visible-light-assisted photocatalytic nitrogen fixation: A titanium metal organic framework with functionalized ligands

The fixation of atmospheric dinitrogen to ammonia is one of the most essential processes for sustaining life. Since the NN bond in dinitrogen is one of the strongest bonds in chemistry, it remains a grand challenge to develop efficient catalysts for fixation of N2 under ambient conditions. Herein we report for the first time on visible-light-assisted photocatalytic nitrogen fixation by metal organic framework material at room temperature and pressure. The Ti3+ species induced by electron transfer from ligand-to-metal charge transfer process provide active sites for N2 reduction. Furthermore, visible-light-assisted photocatalytic N2 fixation is achieved by ligands functionalization which extend the light harvesting of the MOF to visible region. The integration of Ti sites and amine-functionalized linkers in NH2-MIL-125 (Ti) shows the highest visible light photocatalysis efficiency at a rate of 12.3 μmol g−1 h−1. This Ti MOF system therefore shows a potential as a new design of combining light-harvesting and catalytic components in a single solid platform for green NH3 production.