We report the in situ formation of Ni-based supramolecular organogel and organic−aqueous gels using amine appended triazole ligand, having varying morphology and rheological properties. These gels are self-healable and moldable or injectable respectively depending on the absence or presence of water in the gelation medium. Our studies reveal that the formation and rupture of hydrogen bonds assisted by the solvent movement is responsible for the self-healing nature of the gels. The porous structure of the gel has been observed from the migration of dye molecules on the self-healed gel. In addition, the gels show dual function of reversible adsorption of toxic gases and sequestration of heavy metal ions, especially palladium via gel-to-gel transformation. It is imperative to stress that such transformation is extremely rare for small molecule based metallogels. The dynamic nature of Ni−N triazole interactions has been utilized in achieving the reversible gas/vapor responsive behavior of the metallogels, which could be suitable in developing colorimetric probes for the detection of toxic gases and heavy metal ions. Such multifunctional gels are exceptional in contemporary literature and are expected to find utility in fabricating smart multistimuli-responsive gel-based materials in the future.

Supramolecular gels and metallogels involving dynamic and reversible noncovalent interactions are touted as alternatives to gels based on polymeric materials for practical purposes and for an obvious edge in tailorability. A stimuliresponsive Co(II) containing a low-molecular-weight metalloorganogel (CoGel) has been synthesized on a nitrogen-rich triazole platform. CoGel shows autonomous self-healing ability owing to the presence of extensive hydrogen bonding between exocyclic amines of the triazole moiety and the entrapped solvent molecules. CoGel-derived Co-xerogel (xerogel1), having a crumpled sheet-like morphology and a large effective surface area, has been calcined in air to obtain sea-urchin-like Co 3 O 4 . This Co 3 O 4 has been compared with xerogel1 to understand the beneficial effect of the presence of exposed Co(II)-sites, and also, the presence of a ligand that stabilizes both Co 2+ and Co 3+ states, in designing efficient and stable electrocatalysts for oxygen evolution reaction (OER). Both xerogel1 and Co 3 O 4 have shown excellent activity for electrocatalytic OER in acidic and in alkaline media. Combined electrochemical studies revealed that Co 3 O 4 was more stable compared to xerogel1 and, consequently, delivered better activity in an acidic medium, whereas the trend was just reversed in an alkaline medium where xerogel1 was found to be a better catalyst. The xerogel1 in alkaline OER showed a high Faradaic efficiency (FE) of 91.72%, as observed from a rotating ring disc electrode (RRDE) experiment. Moreover, a time course study of O 2 evolution carried out by gas chromatography resulted in a FE in accordance with that observed from the RRDE experiment. Our results are comparable to reported cobalt-based electrocatalysts and introduce possibilities of developing efficient electrocatalytic systems in the future.

The effect of systematic heteroatom doping on carbon-coated metal nanoparticles in enhancing electrocatalytic OER activity was explored using a series of homogeneously dispersed cobalt nanoparticles encased in N,O-dual self-doped carbon onions.