Metal–organic framework@silica as a stationary phase sorbent for rapid and cost-effective removal of hexavalent chromium

Abstract

A one-pot synthesis in quantitative yield is described to construct a composite of the amino-derivative Zr carboxylate metal–organic framework (MOF) and silica gel (UiO-66-NH₂@silica). The silica gel was utilized as a porous solid support to enable enhanced column packing efficiency and increase the sorbent–solute contact time. The control experiment conducted on bare silica unambiguously established the active role of the amino-functionalized MOF as the ion-exchange element in the novel composite. The column prepared from this composite shows excellent hexavalent chromium uptake (Cr₂O₇²⁻ uptake of 277.4 mg g⁻¹). Remarkably, this ion exchange column is capable of eliminating Cr(VI) ions even in the presence of competing anions including chloride, bromide, nitrate and sulphate, thus indicating its potential for applications in municipal as well as industrial waste water treatment.