Selective CO2 adsorption in four zinc(ii)-based metal organic frameworks constructed using a rigid N,N′-donor linker and various dicarboxylate ligands

Abstract

Four new Zn(II)-based metal organic frameworks (MOFs), namely, [Zn(tdc)(4-bpmh)]_n·n(H₂O) (1), [Zn(2-NH₂BDC)(4-bpmh)]_n·n(EtOH) (2), [Zn(NDC)(4-bpmh)]_n (3) and {[Zn(ADPA)(4-bpmh)(H₂O)](ClO₄)}_n·n(MeOH) (4) (tdc = 2,5-thiophene dicarboxylic acid, 2-NH₂BDC = 2-aminoterephthalic acid, NDC = 2,6-naphthalene dicarboxylic acid, ADPA = adipic acid, 4-bpmh = N,N-bis-pyridin-4-ylmethylene-hydrazine) have been synthesized through the slow diffusion technique using a 4-bpmh linker and different dicarboxylic acids. Structural analysis reveals that compounds 1–3 have 3D networks with diamondoid (dia) topologies whereas compound 4 has a 2D pillared-trilayer framework with sql/Shubnikov tetragonal plane net topology. Compounds 1–2 have 6-fold interpenetrated nets and compound 3 is a 7-fold interpenetrated net. Gas adsorption studies reveal that all the compounds 1–4 show selective adsorption of CO₂ over other gases (N₂, CH₄) at low temperature, and the uptake amount of compound 2 is almost double in comparison with those of compounds 1, 3 and 4.