Ni non-equivalent doped La-MOF toward enhanced photocatalytic CO2 reduction through oxygen vacancy regulation and electronic structure optimization

Abstract

Photocatalytic CO2 reduction holds promise for mitigating global warming and achieving carbon neutrality. Metal-organic frameworks (MOFs) are particularly promising as photocatalysts due to their ability to tune metal-oxo cluster electronic structures and facilitate CO2 adsorption. In this study, chemically stable La-MOF modified with Ni-doped metal-oxo clusters has been synthesized through a one-pot solvent-thermal reaction. The experimental and in-situ test results show that the introduction of Ni atoms leads to the formation of oxygen vacancies(VOs)induced by the unsaturated coordination of La/Ni-MOF, which facilitates the adsorption and activation of CO2. The electronic structure of metal oxo (La-O- ) clusters is also effectively regulated, which enhances electron-accepting ability of La-O clusters and promotes the photo-induced electron transfer from the lowest unoccupied molecular orbital (LUMO) of electron donor to the conduction band (CB) of La-MOF. In addition, the additional built-in metal atom (Ni) acts as an active site for CO2 adsorption and activation, achieving effective charge transfer and activated CO2 adsorption integrated construction. The synergy of these effects leads to the optimal La/Ni-MOF withCO selectivity of 96.8% and theyield of 669.3 μmol/g, which is 2.5-fold and more than 5-fold as high as that of the pure La-MOF and Ni-MOF, respectively. This work provides a facile but efficient approach for the construction of coordination unsaturated metal sites and VOs as well as the regulation of the electronic structure of MOFs as efficient photocatalysts towards enhanced performances.