Channel regulation through solvents for Cd‐MOFs based on p‐methoxyphenyl imidazole dicarboxylate: Synthesis, crystal structure, fluorescence, and explosive identification

Abstract

Under different solvent systems, the reaction of Cd(NO 3 ) 2 Á4H 2 O with 2-pmethoxyphenyl-1H-imidazole-4,5-dicarboxylic acid (p-H 3 MOPhIDC) ligand produce two new Cd-MOFs, [Cd(p-HMOPhIDC)(C 2 H 5 OH)] n (1) and [Cd 2 (p-HMOPhIDC) 2 (Py)(C 2 H 5 OH)] n (2). Structural analysis shows that although the two Cd-MOFs have the same six-coordinated distorted octahedron geometry of the Cd(II) centers and the similar framework structure, they have different coordinated polymerization unit symmetry and internal environment in the channels. Among them, the polymerization unit in the channel of Cd-MOFs 1 is centrosymmetric, while the polymerization unit in the channel of Cd-MOFs 2 is asymmetric. Compared with the free p-H 3 MOPhIDC ligand, the fluorescence peaks of the two Cd-MOFs in the solid-state have undergone a slightly red shiftand enhancement. This is due to the increased rigidity of the ligand after the coordination of the metal ions with the ligand, which reduces the energy loss of thermal vibration. The fluorescence enhancement of Cd-MOFs 1 is greater than that of 2, which is related to the symmetry of the coordination polymerization units in the two Cd-MOFs channels. In addition, Cd-MOFs 2 can highly sensitive sense 2,4-dinitrotoluen (DNP) and 2,4,6-trinitrophenol (TNP) through luminescence quenching effect, whereas 1 cannot. This result is due to the difference in the environment within their channels.

Stable Cd Metal–Organic Framework as a Multiresponsive Luminescent Biosensor for Rapid, Accurate, and Recyclable Detection of Hippuric Acid, Nucleoside Phosphates, and Fe3+ in Urine and Serum

“…Crystal Structure. Single-crystal X-ray diffraction analysis shows that the complex 1 crystallizes in the monoclinic 38,39 As shown in Figure 1a, each L 2− ligand connects three Cd 2+ ions, and each Cd 2+ ion in turn is linked by three L 2− ligands, forming a 2D honeycomb layer with hexagonal windows. The adjacent layers are alternately linked by pillared bpbix ligands with two different conformations to afford a pillared-layer 3D framework structure with 1D parallelogram channels (13.6 × 7.7 Å 2 ) along the b axis (Figure 1b).…”

“…Each Cd 2+ ion is hexa-coordinated by three carboxylate O atoms (O1, O3A, and O4A) from two different L 2– ligands, one pyridyl N atom (N1B) from the other L 2– ligand, and two apical imidazolyl N atoms (N4 and N6) from two different pillaring bpbix ligands, displaying a distorted [CdO 3 N 3 ] octahedral geometry (Figure S2). The Cd–O/N bond lengths [2.206(3)–2.481(3) Å] fall into the normal range. , …”