Synthesis and characterisation of strontium carboxylates formed at room temperature and under hydrothermal conditions

Tetrapolymer Network Hydrogels via Gum Ghatti-Grafted and N-H/C-H-Activated Allocation of Monomers for Composition-Dependent Superadsorption of Metal Ions

Herein, gum ghatti (GGTI)-g-[sodium acrylate (SA)-co-3-(N-(4-(4-methyl pentanoate))acrylamido)propanoate (NMPAP)-co-4-(acrylamido)-4-methyl pentanoate (AMP)-co-N-isopropylacrylamide (NIPA)] (i.e., GGTI-g-TetraP), a novel interpenetrating tetrapolymer network-based sustainable hydrogel, possessing extraordinary physicochemical properties and excellent recyclability, has been synthesized via grafting of GGTI and in situ strategic protrusion of NMPAP and AMP during the solution polymerization of SA and NIPA, through systematic multistage optimization of ingredients and temperature, for ligand-selective superadsorption of hazardous metal ions (M(II)), such as Sr(II), Hg(II), and Cu(II). The in situ allocation of NMPAP and AMP via N-H and C-H activations, grafting of GGTI into the SA-co-NMPAP-co-AMP-co-NIPA (TetraP) matrix, the effect of comonomer compositions on ligand-selective adsorption, crystallinity, thermal stabilities, surface properties, swellability, adsorption capacities (ACs), mechanical properties, and the superadsorption mechanism have been apprehended via extensive microstructural analyses of unloaded and/or loaded GGTI-g-TetraP1 and GGTI-g-TetraP2 bearing SA/NIPA in 8:1 and 2:1 ratios, respectively, using Fourier transform infrared (FTIR), 1H/13C/DEPT-135 NMR, X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis, differential scanning calorimetry, X-ray diffraction, field emission scanning electron microscopy, rheological analysis, and energy-dispersive X-ray spectrometry, along with measuring % gel content, pH at point of zero charge (pHPZC), and % graft ratio. The thermodynamically spontaneous chemisorption has been inferred from FTIR, XPS, fitting of kinetics data to pseudo-second-order model, and activation energies. The chemisorption data have exhibited excellent fitting to the Langmuir isotherm model. For Sr(II), Hg(II), and Cu(II), ACs were 1940.24/1748.36, 1759.50/1848.03, and 1903.64/1781.63 mg g-1, respectively, at 293 K, 0.02 g of GGTI-g-TetraP1/2, and initial concentration of M(II) = 500-1000 ppm.

A novel three-dimensional SrII coordination polymer based on benzene-1,2,4,5-tetracarboxylate: hydrothermal synthesis, crystal structure and spectroscopic and thermal studies

Coordination of the anions of benzenecarboxylic acids with metal cations leads to coordination polymers with various structural features. Very few examples of strontium-based structures have been reported. A new three-dimensional coordination polymer, namely poly[aqua(μ12-benzene-1,2,4,5-tetracarboxylato)distrontium(II)], [Sr2(C10H2O8)(H2O)] n , has been synthesized under hydrothermal conditions and characterized by thermal analysis, vibrational spectroscopy (Raman and IR), single-crystal X-ray diffraction and powder X-ray diffraction. The coordination geometries around the two independent SrII ions can be described as a distorted dodecahedron and a distorted monocapped square antiprism. The compound features a three-dimensional structure containing inorganic motifs, with two-dimensional layers connected through organic linkers, and possesses a topologic structure of a binodal (6,12) connected alb net with the Schläfli symbol {415}2{448.618}. The final product of thermal decomposition is strontium oxide (SrO).