Metal-organic frameworks based on flexible bis(imidazole) and dicarboxylic ligands and their applications as selective sensors for magnesium nitrate

Abstract Three new MOFs, namely {Co2(Bbi)2(A)2·H2O}n (1), {Co(Bbi) (B)2·4H2O)}n (2) and {Cd6(Bbi)1.5(L)6·5H2O}n (3) [Bbi = 1,1′-(1,4-butanediyl)bis(imidazole), H2L = (anthracene-9,10-endo-succinic acid), H2A = (benzopheno-4,4-dicarboxylic acid), H2B = (1,2-diethyl ether-4,4′-dibenzoic acid)], have been constructed through hydrothermal synthesis. 1 exhibits a double interpenetrating 3D to 3D cds topology network with point symbol of {65.8}. 2 forms a large 3D channel by ligand Bbi connected 2D adjacent waveform layers, displaying 4-connected net with sql topology defined by the point symbol of {44·62}. A rare hexa-nuclear Cd cluster can be observed in the structure of 3 with a Schlafli symbol of {42·6}2{43·103}{43·6·82}{43·63}{44·62}2{45·62·82·10}{46}4. TG analyses indicate the highly thermal stability of 1–3. More importantly, MOFs 1–3 can be developed as fluorescent sensors, which show high selectivity towards magnesium nitrate among various metal nitrates in CH3CN by fluorescence quenching, presenting as promising candidates for chemical sensing.