Metal-nonmetal co-doping in Ti-MOF toward efficient photocatalytic nitrogen fixation

Engineering the electron transfer pathway in metal-organic frameworks (MOFs) is crucial for photocatalytic nitrogen fixation. This study proposes a metal-nonmetal co-doping strategy to interconnect the metal-to-metal charge transfer (MMCT) pathway with the ligand-to-metal charge transfer (LMCT) pathway in Ti-based MOFs for boosted electron transfer. A series of B and Co co-doped NH 2 -MIL-125, denoted as NBM(Ti/Co), were designed and synthesized by a one-pot hydrothermal method. In the NBM(Ti/Co), the doped B atom with the electron-deficient property promotes the electron transfer through the ligand to the metal node pathway, while the doped Co 2+ with a lower ionization energy than Ti 4+ opens up an inter-metal electron transfer pathway. These two pathways converge at the Ti 4+ active site, generating an integrated B-Co-Ti electron-transfer network that shuttles photogenerated electrons, facilitating the charge separation and migration. The optimal NBM(Ti/Co) sample achieves a high ammonia production rate of 379.2 μmol/(g·h) under full-spectrum irradiation, which is 4.2-fold greater than that of pristine NH 2 -MIL-125. This study opens an avenue to designing high-performance MOF-based photocatalysts through a metal-nonmetal co-doping strategy.