Bimetallic CeZr5-UiO-66 as a highly efficient photocatalyst for the nitrogen reduction reaction

Abstract

Metal node substitution in metal organic frameworks is an efficient strategy to enhance their photocatalytic properties. Herein, bimetallic CeZr₅-MOF UiO-66 photocatalysts were successfully synthesized by partially replacing Zr with Ce for enhancing the photocatalytic N₂ reduction reaction (NRR). The rare earth element Ce was introduced into the node of Zr-MOFs (UiO-66) to form CeZr₅ clusters, which enhanced the efficiency of photoexcited electron–hole pair separation and charge transfer via the ligand-to-metal charge transfer process (LMCT), thus promoting the photocatalytic nitrogen fixation performance. Photocatalytic properties increase linearly with the increase of Ce content. Higher Ce proportions (>20%) resulted in new MOFs (Ce-BDC-24) with low photocatalytic activity. The bimetallic system showed enhanced photocatalytic activities for N₂ reduction, which was 105.9% higher than that of Zr-UiO-66 and reached 200.13 μmol g⁻¹ h⁻¹. Furthermore, the possible energy transfer mechanism was proposed to explain the photo-induced charge transfer process in the bimetallic UiO-66(CeZr₅) system.