Rapid synthesis of cerium-UiO-66 MOF nanoparticles for photocatalytic dye degradation

Abstract

An unprecedented synthesis method is used to form a series of Ce-UiO-66-X (X = NH₂, OH, H, NO₂, COOH) metal–organic frameworks by precipitation from mixed solvents, with instantaneous crystallisation on combining separate solutions of ligands and metal precursors. This allows the first direct synthesis of Ce-UiO-66-OH. Powder X-ray diffraction (PXRD) shows that all materials are pure phase with a broadened profile that indicates nano-scale crystallite domain size. The effect of different functional groups on the benzene-1,4-dicarboxylate linker within the UiO-66 structure has been investigated on degradation of two cationic (methylene blue and rhodamine B) and two anionic (Congo red, and Alizarin red S) dyes under UV and visible light irradiation at room temperature. Analysis of the dye adsorption in the absence of light is accounted for using pseudo-first order kinetics, and the Ce-UiO-66-NH₂, Ce-UiO-66-OH, and Ce-UiO-66-H materials display a considerable photocatalytic activity to degrade Alizarin red S and Congo red rapidly between 1 and 3 minutes. The materials show excellent photostability and recyclability under UV and visible light, with no loss of crystallinity seen by PXRD and activity maintained over 5 cycles, with 16 hours photostability for Ce-UiO-66-NH₂.