Metal–Organic Gels Based on a Bisamide Tetracarboxyl Ligand for Carbon Dioxide, Sulfur Dioxide, and Selective Dye Uptake

Abstract

A metal-organic gel (metallogel) based on the new tetracarboxyl ligand N¹, N⁴-(diterephthalic acid)terephthalamide in combination with chromium(III) has been converted into its xero- and aerogel and demonstrated to have excellent specific sorption properties for dyes in its metallogel state, where fuchsine is adsorbed faster than the two other dyes, calcein and disulfine blue, and for water, sulfur dioxide and carbon dioxide in its xero- and aerogel state. The metallogel showed very good shape retention and could be extruded from molds in designed shapes. In a rheology experiment, the storage modulus was determined to be 1440 Pa, and the metallogel is elastic up to 3 Hz, breaking at strains higher than 0.3%. Additional metallogels utilizing the same ligand with a wide range of metal ions (Al(III), Fe(III), Co(III), In(III), and Hg(II)) have also been synthesized, and the aluminum and mixed aluminum-chromium derivative were also converted into its aerogel. The highly porous Cr, Al, and AlCr metal-organic aerogels proved stable against water vapor in a physisorption experiment and were used to model breakthrough curves for SO₂/CO₂ gas mixtures with the idealized adsorbed solution theory from their physisorption isotherms. The breakthrough simulation utilized SO₂/CO₂ equivalencies from a real world application and showed effective retention of SO₂ from the gas mixture. Furthermore, the materials in this work exhibit the highest SO₂ uptake values for metal-organic aerogels so far (up to 116.8 cm³ g^-1, or 23.4 wt %).