Visible-Light-Driven Sonophotocatalysis for the Rapid Reduction of Aqueous Cr(VI) Based on Zirconium–Porphyrin Metal–Organic Frameworks with csq Topology

Abstract

Photochemical treatment of highly toxic Cr(VI) is a desirable and ecofriendly method to protect the environment and human beings. In this study, a MOF-based sonophotocatalytic system is established, in which visible-light-driven sonophotocatalytic reduction of toxic Cr(VI) to Cr(III) in water is investigated using zirconium−porphyrin metal−organic frameworks (MOFs) structured as PCN-222(M) [M = H 2 , Zn(II), Fe(III), Co(II)]. In the view of the synergistic effect of sonochemistry and photocatalysis, PCN-222(M) exhibited enhanced activities for Cr(VI) reduction compared with the photocatalytic process. Kinetic studies showed that apparent reaction rate constants in the sonophotocatalytic system of PCN-222(M) are 1.5−3.3 times higher than those in photocatalysis. Fluorescence and UV−vis absorption spectra measurements demonstrate that the sonophotocatalytic process promotes the transfer of photoinduced electrons from to Cr(VI), thus enhancing the catalytic performance. The innovative combination of porous MOFs and sonophotocatalytic technology might become a feasible strategy to improve the existing MOF-based photocatalytic systems.

Recent Progress in the Development of MOF-Based Photocatalysts for the Photoreduction of Cr(VI)

“…Chen et al reported a synergistic effect of sonochemistry and photocatalysis by applying PCN-222­(Fe III , Co II , Zn II ). The MOFs exhibited 1.5–3.3 times higher rate constants in the photoreduction of Cr (VI) assisted by sonication waves (20 kHz, 30–120 W) under visible-light irradiation.…”

“…Mechanism of the Cr (VI) photoreduction by PCN-222. Reprinted with permission from ref . Copyright 2021 American Chemical Society.…”

Visible-light-driven sonophotocatalysis for enhanced Cr(vi) reduction over mixed-linker zirconium-porphyrin MOFs

“…[43][44][45][46] However, MOF materials used for sonophotocatalytic Cr(VI) reduction are rarely reported until now. 47 In this work, two mixed-linker zirconiumporphyrin MOFs, namely PCN-134 and PCN-138, were synthesized and characterized. In the light of the good photophysical properties of the two zirconium-porphyrin MOFs, the performance of sonophotocatalytic reduction of aqueous Cr(VI) driven by visible light was comparatively studied.…”

Visible-light-driven photocatalytic CO2 reduction to formate over a zirconium-porphyrin metal–organic framework with shp-a topology

“…Metal-organic frameworks (MOFs), a special kind of porous hybrid materials, have received significant attention in the photochemical conversion field due to their modular nature and facile tunability. [10][11][12][13][14][15] More importantly, the photophysical properties of MOFs can be conveniently regulated at the molecular level with the help of abundant inorganic and organic building blocks. [16][17][18] In recent years, MOFs as heterogeneous catalysts have made notable progress in photoreduction of CO 2 to high added-value products.…”