The synthesis and combined electrical–magnetic and toxic dye sequestration properties of a Cr(iii)-metallogel

Abstract

Materials based on typical inorganic compounds, along with their embodied metal-specific features like redox, magnetic, catalytic and spectroscopic properties, in their as-synthesized economical, end-user friendly and commercially viable gel states, have manifold practical and strategic advantages. Along these lines, the work presented herein aims to explore the usefulness of porous gel-based inorganic compounds, in their original as-synthesized states, for probing their combined electrical, magnetic and adsorption properties. Accordingly, we have synthesized and thoroughly characterized a benzene dicarboxylic acid based Cr(III)-metallogel for magnetic and electrical device fabrication. The metallogel shows an interesting NMOP morphology and is thoroughly characterized using various microscopic and spectroscopic techniques. Furthermore, rheological studies on the resultant metallogel reveal its interesting thixotropic behaviour. The Cr-gel has been successfully utilized for fabricating an electrical Schottky barrier diode with a befitting conductivity value of 1.61 × 10⁻² S cm⁻¹. Moreover, the free immobilized azide group, featuring in-built charge-separated resonance structures, acts as a proton carrier facilitator-cum-transporter and shows an impressive proton conductivity value of 3.3 × 10⁻⁴ S cm⁻¹ at 95% relative humidity and 85 °C. The presence of paramagnetic chromium ions also renders a special physicochemical property, namely magnetism, to the system. The porous and magnetic nature of the as-synthesized metallogel was also evaluated. DC magnetic susceptibility data confirm the antiferromagnetic nature of the material. Gas sorption studies, on the other hand, confirm the porous nature and show the selective CO₂ uptake ability of the xerogel. Subsequently, the as-synthesized, by default porous, magnetic metallogel was utilized as an adsorbent for removing toxic organic dyes like methylene blue, rhodamine B and crystal violet. Interestingly, the as-prepared metallogel also enables the substantial release of the adsorbed dye molecules for re-use. To the best of our knowledge, this kind of electrical–magnetic Cr-gel based wastewater treatment technique was not reported hitherto in the literature but has a huge potential application in adsorbent based environmental remediation as well as in magnetic or electrical device fabrication.