Constructing Cu2+active sites on pyrazole-decorated UiO-66-NH2 with high activity for photocatalytic CO2 reduction to HCOO-

Building catalytic metal sites are considered to be promising for improving certain photocatalytic reactions. Herein, a novel Cu2+ functionalized MOF named Cu2+@UiO-66-AMpz was fabricated by two facile post-synthetic modification. The electron paramagnetic resonance analysis, together with the results of the measurements manifested that the introduction of single Cu2+ sites could sustain supply of photogenerated electrons and the transient Cu2+/Cu + centers served as effective photocatalytic sites for CO2 reduction. As a result, Cu2+@UiO-66-AMpz exhibited a very high HCOO-production rate of 956.2 mu mol g-1 h-1 with 94.4 % selectivity after 4 h, which was about 16 times higher than that of the pristine UiO-66-NH2. The mechanism analysis revealed that the high HCOO-production rate was attributed to strong CO2 absorption and the generation of key *OCOH intermediates. This work provides a way to create single metal catalytic sites for highly effective photocatalytic CO2 reduction.