A new set of Cd(ii)-coordination polymers with mixed ligands of dicarboxylate and pyridyl substituted diaminotriazine: selective sorption towards CO2 and cationic dyes

Abstract

On the basis of a mixed ligand system of L(NH₂)₂ (6-(pyridin-4-yl)-1,3,5-triazine-2,4-diamine) and dicarboxylic acids, three new Cd(II) coordination polymers viz. {[Cd_0.5(tdc)_0.5(L(NH₂)₂)_0.5(H₂O)]·DMF·H₂O}_n (1), {[Cd_0.5(bdc)_0.5(L(NH₂)₂)(H₂O)]·DMF·H₂O}_n (2), and {[Cd(ipa)(L(NH₂)₂)(DMF)]·H₂O}_n (3) (tdcH₂ = thiophene-2,5-dicarboxylic acid, bdcH₂ = benzene-1,4-dicarboxylic acid, ipaH₂ = benzene-1,3-dicarboxylic acid) were synthesized under diverse reaction conditions and characterized by single crystal X-ray diffraction, PXRD, elemental analysis, IR spectroscopy and TGA. While 1 and 2 revealed 1D chain structures, 3 acquired a 2D square net structural arrangement. Gas adsorption measurements of the desolvated framework 3 showed a moderate uptake of CO₂ under ambient conditions with good selectivity over N₂ and CH₄. The solid state luminescence properties were studied for all three coordination polymers. Moreover, a dye adsorption study on 3 exhibited selective adsorption towards a cationic dye.