Highly sensitive detection of nitrobenzene by a series of fluorescent 2D zinc(ii) metal-organic frameworks with a flexible triangular ligand.

Four fluorescent zinc(ii) metal-organic frameworks, namely [Zn(HCIA)(4,4'-bipy)] (1), [Zn2(CIA)(OH)(1,4-bibz)1.5]·H2O (2), [Zn(CIA)(OH) (4,4'-bbpy)] (3), and [Zn2(HCIA) (4,4'-bimp)]·H2O (4), were prepared hydrothermally with a flexible triangular ligand (H3CIA) and a series of linear N-donor ligands (H3CIA = 5-(2-carboxybenzyloxy) isophthalic acid, 4,4'-bipy = 4,4'-bipydine, 1,4-bibz = 1,4-bis(1-imidazoly)benzene; 4,4'-bbpy = 4,4'-bis (imidazolyl) biphenyl; 4,4'-bimp = 4,4'-bis (imidazole-1-ylethyl) biphenyl). Structural analyses revealed that complex 1 exhibited a 2D brick-like network structure based on the basic bimetallic ring, 2 was also a 2D interspersed structure from the 1D tubular structure, compound 3 possessed a 2D (4,4) network with 4,4'-bbpy occupying the holes, and complex 4 displayed a 2D network from the 1D ladder-like chain. The thermal stabilities and fluorescent properties of these complexes were investigated in the solid state. The fluorescent sensing experiments revealed that all Zn-MOFs could highly sensitively detect nitrobenzene in aqueous solution, which indicated that these materials can be used as fluorescent probes for the detection of nitrobenzene.