Photocatalytic Reduction and Recognition of Cr(VI): New Zn(II)-Based Metal–Organic Framework as Catalytic Surface

Abstract

This report deals with the fabrication and utilization of a novel 2D zinc-based metal−organic framework (MOF) {[Zn(PA 2− )(4,4′-bpy)]-(H 2 O)} n (where PA = pamoic acid and 4,4′-bpy = 4,4′-bipyridine). The Zn-MOF has been synthesized via a solvothermal method and emanates green fluorescence. As Cr(VI) is a fatal and carcinogenic ion, it is extremely important to discern and remove it from nature. The bright green fluorescence of Zn-MOF can be quenched upon interaction with a Cr 2 O 7 2− ion, which implies the MOF's applicability as a Cr(VI) detector through turn-off fluorescence signaling. On the contrary, among various strategies to remove Cr(VI), the photocatalytic reduction of Cr(VI) to Cr(III) is acknowledged as the most effective one. Delightfully, apart from being a Cr(VI) sensor, this same Zn-MOF can be further recruited as a photocatalyst to convert Cr(VI) to Cr(III). The catalytic reduction is triggered by natural sunlight, acidic pH, and a hole scavenger. In addition, good stability and reusability of the Zn-MOF satisfies the quest for a potential photocatalyst for conversion of Cr(VI) to Cr(III). The limit of detection for fluorometric recognition of Cr(VI) was found to be 4.12 μM, and almost a complete reduction of toxic Cr(VI) ion was achieved.

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

“…Previous studies reported that pH values had great influence on reducing Cr( vi ) by photocatalysis. 52–56 In order to obtain the optimal reaction conditions, control experiments were performed with different pH conditions. When the pH value decreases from 4 to 1, the photocatalytic efficiency of PCN-134 and PCN-138 was improved.…”

The enhanced visible-light-induced photocatalytic activities of bimetallic Mn–Fe MOFs for the highly efficient reductive removal of Cr(vi)

“…Knowing that Cr( vi ) reduction is favored at low pH conditions, 25 the preliminary tests for Cr( vi ) reduction were performed at pH = 2 at ambient temperature in darkness and sunlight, in the absence and presence of catalyst and with ethanol as hole scavenger (for more information on catalyst identification and data analysis, see ESI † and ref. 19 ).…”

Fabrication of a novel heteroepitaxial structure from an MOF-on-MOF architecture as a photocatalyst for highly efficient Cr(vi) reduction

“…The main reason for this broad-range absorption is the energy-transfer process to the metal ions from the ligands, which is a typical property of carboxylic acid-based MOFs. 47,48 Fig. 5b shows the (ahn) 2 versus hn curves of the MOFs.…”