Chemical and Mechano Responsive Metal-Organic Gels of Bis(benzimidazole)-Based Ligands with Cd(II) and Cu(II) Halide Salts: Self Sustainability and Gas and Dye Sorptions

The pyridine-3,5-bis(benzimidazole-2-yl) ligand (L) with metal salts (Cu(II) or Cd(II)) has been found to gelate several aliphatic alcohols to generate multifunctional metal-organic gels (MOGs). The anions of the metal salt were found to play an important role in the gelation property; halides (chlorides or bromides) and sulphates were found to be more effective than other univalent ions such as nitrate, aceteate, perchlorate, and tetrafluoro borate. The microscopic investigation with FESEM, TEM, POM, and AFM confirmed the formation of interwinding 3D gel fibrous networks, which have immobilized the large volume of solvent. The coordination of the metal to the ligand L was found to play a vital role in the construction of gel fibers. Rheology studies on the MOGs revealed that these MOGs have significantly high mechanical strengths and therefore exhibit self-sustainability. The porous nature of the MOGs has been explored by gas sorption studies; xerogels show the type-III N-2-sorption isotherm. The MOGs have also shown a tendency as potent dye removal agents. These gels also exhibited thermo irreversibility but mechano reversibility. The sol-gel transformations were observed through applying external chemical stimuli, that is, by adding metal capturing agents.