Abstract
A pair of cobalt(II)-based hydrogen-bonded organic frameworks (HOFs), [Co(pca)2(bmimb)]n (1) and [Co2(pca)4(bimb)2] (2), where Hpca = p-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 1 has a one-dimensional (1D) infinite chain network through the deprotonated pca− monodentate chelation and with a μ2-bmimb bridge Co(II) atom, and 2 is a binuclear Co(II) complex construction with a pair of symmetry-related pca− and bimb ligands. For both 1 and 2, each cobalt atom has four coordinated twisted tetrahedral configurations with a N2O2 donor set. Then, 1 and 2 are further extended into three-dimensional (3D) or two-dimensional (2D) hydrogen-bonded organic frameworks through C–H···Cl interactions. Topologically, HOFs 1 and 2 can be simplified as a 4-connected qtz topology with a Schläfli symbol {64·82} and a 4-connected sql topology with a Schläfli symbol {44·62}, respectively. The fluorescent sensing application of 1 was investigated; 1 exhibits high sensitivity recognition for Fe3+ (Ksv: 10970 M−1 and detection limit: 19 μM) and Cr2O72− (Ksv: 12960 M−1 and detection limit: 20 μM). This work provides a feasible detection platform of HOFs for highly sensitive discrimination of Fe3+ and Cr2O72− in aqueous media.
Highlights
A new class of materials named hydrogen-bonded organic frameworks (HOFs) has emerged as an exciting class of compounds stabilized by non-covalent hydrogenbonding and π−π stacking interactions [1,2,3,4,5]
The metal-organic frameworks (MOFs) and covalent-organic frameworks (COFs) are usually connected by coordination bonds or covalent bonds between atoms and show relatively high stabilities [12,13,14,15,16,17,18,19,20], while the HOFs are linked by weak non-covalent interactions, such as hydrogen bonds and π−π stacking interactions, and exhibit relatively low stabilities [21,22,23,24,25]
Each Co ion is tetra-coordinated with two O atoms (O1 and O1i, symmetry code i seen in Table S2) and two N atoms (N1 and N1i) from two symmetry-related pac− and bmimb ligands, resulting in a slightly distorted tetrahedron geometry (Figure 1b)
Summary
A new class of materials named hydrogen-bonded organic frameworks (HOFs) has emerged as an exciting class of compounds stabilized by non-covalent hydrogenbonding and π−π stacking interactions [1,2,3,4,5]. The metal-organic frameworks (MOFs) and covalent-organic frameworks (COFs) are usually connected by coordination bonds or covalent bonds between atoms and show relatively high stabilities [12,13,14,15,16,17,18,19,20], while the HOFs are linked by weak non-covalent interactions, such as hydrogen bonds and π−π stacking interactions, and exhibit relatively low stabilities [21,22,23,24,25]. For HOFs, the solvent guests play important roles in the construction of the supermolecular network system. Once the solvent guests are removed, the supermolecular system is usually broken, and the HOFs collapse. It is unsurprising that, thousands of HOFs have been reported in the literature during the last two decades, examples of HOFs with permanent stable are very rare [26,27]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
