One-pot synthesis of Ni(Ⅱ)-doped UiO-66-NH2 for enhanced photocatalytic CO2 reduction to CO with efficient charge transfer

Introducing a new metal into the metal center of metal–organic framework materials (MOFs) to alter their original electron transfer pathway to improve photocatalytic performance is a promising approach at present. Here, we report a one-pot method to introduce Ni2+ into the metal-centered Zr-O clusters of UiO-66-NH2 (UN) to create a series of Ni2+-doped bimetallic materials (xNi-UN). Experimental results showed that the 0.5Ni-UN exhibited the highest photocatalytic CO2 reduction activity, with a CO yield of 9.01 µmol g-1h−1 under visible light irradiation, which was 2.46 times higher than that of UN (3.67 µmol g-1h−1). Through a number of characterization analyses, we find that the doped Ni2+ replaced the part of original metal center Zr4+ to form a bimetallic UiO-66-NH2 (Zr/Ni), which changed the energy band gap of UiO-66-NH2 and improved the charge transfer. More importantly, the introduction of Ni2+ enhanced the efficiency of interfacial charge transfer from the organic ligand (2-aminoterephthalic acid) to the Zr-O cluster, enabling a metal-to-metal charge transfer (MMCT) pathway, which exhibited higher photocatalytic CO2 to CO reduction activity.