Syntheses, structures, surface analysis, DFT and fluorescence properties of three new Cd(II)-MOFs assembled with semi-rigid polycarboxylate

Abstract

Three Cd(II)-based metal-organic frameworks (MOFs), namely, [Cd(HL1)(4,4′-bipb)]n(1), [Cd2(L2)(4,4′-bipb)2(H2O)3]n (2), {[Cd2(L3)(4,4′-bipb)(H2O)2]·(4,4′-bipb)0.5}n (3), where H3L1, H4L2, H4L3, and 4,4′-bipb are semi-rigid 2-(4-carboxyphenoxy) terephthalic acid, 3-(2,4-dicarboxyphenoxy)phthalic acid, 3,3′-(1,3- phenylenebis(oxy))diphthalic acid, and 1,4-bis(pyridin-4-yl)benzene, respectively, are synthesized in the presence of 4,4′-bipb and Cd(II) ions by hydrothermal method. 1 displays a 2,6-connected 3D topological structure. 2 features a 3D framework with 4,5,5-connected topology. 3 shows a 4,4,4-connected 3D topology. The fluorescence properties of 1–3 were determined in a dilute aqueous suspension at room temperature. The initial fluorescence intensity of 1 and 2 was almost completely quenched after the addition of Fe(NO3)3 solution. It is confirmed that after the addition of AgNO3 solution, the fluorescence intensity of 3 was quenched significantly, but the fluorescence intensity is increased after the Al(NO3)3 and Fe(NO3)3 solutions are added.