Enhanced photocatalytic nitrogen fixation on defects regulated Ni-doped MIL-101(Fe) via nitrogen coordinated activation

Abstract

Defect engineering is a promising strategy for alleviating the challenges associated with the quick recombination of charge and N2 activation. In this study, MIL-101(Fe/Ni)-X% with different oxygen vacancy concentrations were synthesized by introducing Ni into MIL-101(Fe) for photocatalytic nitrogen fixation. The optimal catalyst MIL-101(Fe/Ni)-15% achieved an ammonia production rate of 66.3 μmol⋅g -1 ⋅h -1 , which is much greater than that of MIL-101(Fe). The results indicate that Ni doping results in the absence of oxygen coordinated with Fe, which generates the Fe 2+ site and oxygen vacancy. The unsaturated Fe 2+ coordination site can effectively adsorb and activate N2. Moreover, vacuum heat treatment further regulates the oxygen vacancy concentration. An appropriate amount of oxygen vacancies is conducive to optimizing the utilization of interface holes and the separation of photogenerated charges. This work offers a novel approach for the photocatalytic nitrogen fixation by synergistically modifying MOF materials through metal doping and defect engineering.