Facile fabrication and enhanced photocatalytic performance of visible light responsive UiO-66-NH2/Ag2CO3 composite

A series of UiO-66-NH 2 /Ag 2 CO 3 Z-scheme heterojunctions were prepared by a simple ion-exchange-solution method using UiO-66-NH 2 and semiconductor Ag 2 CO 3 as precursors. The photocatalytic activities of UAC- X (UAC-20, 50, 100, 150, 200) Z-scheme heterojunctions toward the hexavalent chromium (Cr(VI)) reduction and UAC-100 toward oxidative degradation of four organic dyes like rhodamine B (RhB), methyl orange (MO), congo red (CR), and methylene blue (MB) under visible light irradiation were investigated. The effects of different pH (pH = 2, 3, 4, 6, 8), small organic acids (citric acid, tartaric acid, and oxalic acid), and foreign ions (ions in tap water and surface water) on Cr(VI) reduction were explored. The results revealed that the UAC-100 heterojunctions displayed more remarkable Cr(VI) reduction performance than the pristine UiO-66-NH 2 and Ag 2 CO 3 , resulting from the improved separation of photo-induced electrons and holes. The enhanced photocatalytic activity of UAC-100 was further confirmed by the photoluminescence measurement, electrochemical analysis, and active species trapping experiments. After four cycles' experiments, the photocatalytic Cr(VI) reduction efficiency over UAC-100 was still over 99%, which exhibited that UAC-100 had excellent reusability and stability. Finally, the corresponding photocatalytic reaction mechanism was proposed and tested. The UiO-66-NH 2 /Ag2CO 3 composite (UAC-X) displayed outstanding photocatalytic activity due to the effective separation of photo-induced electrons and holes over the composite, which was contributed to the formed direct Z-scheme heterojunctions.