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(PA2–)(4,4′-bpy)](H2O)}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 Cr2O72– 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.