Fine-tuning the balance between crystallization and gelation and enhancement of CO2 uptake on functionalized calcium based MOFs and metallogels

Abstract

The synthesis, structure, gas adsorption and catalytic properties of a new 3D porous, crystalline metal-organic framework (Ca-5TIA-MOF) as well as stable viscoelastic metallogels (Ca-5TIA-Gel) are reported. Remarkably, the preparation of both types of materials can be carried out starting from the same organic ligand (i.e. 5-(1,2,4-triazoleyl)isophthalic acid (5TIA)), divalent metal ion (i.e. Ca(II)) and organic solvent (i.e. DMF). In this particular case, the presence of water in the solvent system favors the formation of a crystalline MOF, whereas a pure organic solvent induces gelation. The characterization of the materials was carried out using a series of techniques including XRD, FT-IR, TGA, TEM, SEM, SAXS and dynamic rheology. Experimental PXRD peaks of both Ca-5TIA-xerogel and Ca-5TIA-MOF matched reasonably well with simulated PXRD, suggesting the presence of, at least, some common structural elements in the 3D networks of both xerogel and crystalline phases. Moreover, the nature of the metal counteranion was found to have a critical influence on the gelation phenomenon. To the best of our knowledge, this report describes unprecedented Ca-based LMW-metallogels, as well as the first porous Ca-based MOF, which shows adsorption capacity for CO 2 at 1 atm pressure. Interestingly, Ca-5TIA-xerogel presented 20% higher CO 2 -uptake than the crystalline Ca-5TIA-MOF at 1 atm and 298 K. Both Ca-5TIA-MOF and Ca-5TIA-Gel also displayed a modest catalytic activity towards the hydrosilylation of benzaldehyde, with slightly better performance for the gel phase material.

Versatile Barium and Calcium Imidazolium‐Dicarboxylate Heterogeneous Catalysts in Quinoline Synthesis

“…The group of Monge and Gutiérrez‐Puebla has employed the linker anthraquinone‐2,6‐disulfonate with calcium and barium to generate heterogeneous catalysts for styrene hydrogenation and diphenylsilylation of benzaldehyde . Additionally, calcium has been linked with 4,4′‐(hexafluoroisopropylidene)bis(benzoate) to prepare a catalyst for styrene hydrogenation, and connected with 5‐(1,2,4‐triazol‐4‐yl)isophthalate to obtain a catalyst for diphenylsilylation of benzaldehyde …”

Recent Advances in Supramolecular Gels and Catalysis

“…In addition to the above‐mentioned ligands modified with pyridine moieties, ligands with imidazolyl groups, carboxylic groups, and phosphines were also selected to coordinate with metal ions for metallogel fabrication . According to the results from You and co‐workers, a Pd‐metallogel derived from ligand 5 and Pd(OAc) 2 could efficiently trigger the phenylation of indole with phenyl boronic acid (Figure ) .…”

Coordination‐Driven Terpyridyl Phosphine Pd(II) Gels

“…Recently we and others use rigid bridging ligands to react with metal ions to obtain a novel class of coordination-driven metal-organic gels. [9,11,[46][47][48][49][50][51][52] These metal-organic gels have sponge-like porous structures and show potential applications in adsorption and catalysis. Herein we use this coordination-driven strategy to prepare Pd-phosphine gels from rigid terpyridyl phosphines so that Pd-phosphine catalytically active motifs are incorporated into the gels.…”