Modulation of the charge transfer behavior of Ni(II)-doped NH2-MIL-125(Ti): Regulation of Ni ions content and enhanced photocatalytic CO2 reduction performance.

• A series of NH 2 -MIL-125-Ni 0.5-1.5% /Ti photocatalysts are in situ synthesized. • The prepared NH 2 -MIL-125-Ni 0.5-1.5% /Ti exhibits enhanced CO 2 reduction activity. • The electronic structure of (Ti/Ni) 8 O 8 (OH) 4 nodes has effect on MOF's band structure. • The Ni2+ induced electronic structure change of (Ti/Ni) 8 O 8 (OH) 4 nodes are analyzed. • The Ni2+ dopants sites are discussed based on the electrostatic potential analysis. Regulation of the electronic structure of metal oxo clusters in metal organic frameworks (MOFs) is a promising way to modulate charge transfer efficiency and photocatalytic performance. Herein, a series of Ni2+ doped NH 2 -MIL-125-Ti (NH 2 -MIL-125-Ni x /Ti) with different Ni2+/Ti4+ molar ratio (x = 0.5%–1.5%) are prepared via an in-situ doping method. Correlations between the electronic structure of (Ti/Ni) 8 O 8 (OH) 4 nodes and charge transfer efficiency, bandgap and energy position of band edges of the NH 2 -MIL-125-Ni x /Ti are systematically investigated based on experimental and computational method. The doped Ni2+ was confirmed to be an efficient mediator to promote the electron transfer from photoexcited terephthalate ligand to the (Ti/Ni) 8 O 8 (OH) 4 nodes in NH 2 -MIL-125-Ni x /Ti. The NH 2 -MIL-125-Ni 1% /Ti exhibited the highest CO 2 conversion rate with 98.6% CO selectivity and the factors affecting the photocatalytic CO 2 reduction performance are also studied. It provides some guidance for developing MOFs photocatalyst with targeted performance via modification of the electronic structure of metal oxo clusters. [ABSTRACT FROM AUTHOR]