Construction of Two Stable Co(II)-Based Hydrogen-Bonded Organic Frameworks as a Luminescent Probe for Recognition of Fe and CrO in HO.

A pair of cobalt(II)-based hydrogen-bonded organic frameworks (HOFs), [Co(pca)(bmimb)] () and [Co(pca)(bimb)] (), where Hpca = -chlorobenzoic acid, bmimb = 1,3-bis((2-methylimidazol-1-yl)methyl)benzene, and bimb = 1,4-bis(imidazol-1-ylmethyl)benzene were hydrothermally synthesized and characterized through infrared spectroscopy (IR), elemental and thermal analysis (EA), power X-ray diffraction (PXRD), and single-crystal X-ray diffraction (SCXRD) analyses. X-ray diffraction structural analysis revealed that has a one-dimensional (1D) infinite chain network through the deprotonated pca monodentate chelation and with a μ-bmimb bridge Co(II) atom, and is a binuclear Co(II) complex construction with a pair of symmetry-related pca and bimb ligands. For both and , each cobalt atom has four coordinated twisted tetrahedral configurations with a NO donor set. Then, and are further extended into three-dimensional (3D) or two-dimensional (2D) hydrogen-bonded organic frameworks through C-H···Cl interactions. Topologically, HOFs and can be simplified as a 4-connected topology with a Schläfli symbol {6·8} and a 4-connected topology with a Schläfli symbol {4·6}, respectively. The fluorescent sensing application of was investigated; exhibits high sensitivity recognition for Fe (: 10970 M and detection limit: 19 μM) and CrO (: 12960 M and detection limit: 20 μM). This work provides a feasible detection platform of HOFs for highly sensitive discrimination of Fe and CrO in aqueous media.