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In this paper, the functionalized ligand 2-(imidazole-1-yl)terephthalic acid was obtained by grafting an imidazole group onto 2-bromoterephthalic acid. Then, defective MOFs were synthesized with Hf ions and the ligand in the presence of monocarboxylic acid acting as a modulator, and NHC (nitrogen heterocyclic carbene)–CO2 adducts were grafted onto the Hf-based MOFs to catalyze the cycloaddition reaction of epoxides with CO2 to produce cyclic carbonates under green conditions of ambient pressure and being solvent- and cocatalyst-free. The mesopore defects created by the modulator and DMC (dimethyl carbonate) solvothermal etching, the enhanced Lewis acidity of the Hf clusters and the grafted NHC–CO2 adducts can improve synergistically the catalytic performance of the MOFs via decreasing activation energy, promoting mass transfer and providing more active catalytic sites. The results show that the highest conversion rate reaches 81.64% at 100 °C and 10 h for the cycloaddition reaction of CO2 with epichlorohydrin. Finally, a possible reaction mechanism was proposed based on characterization and catalytic measurement. [ABSTRACT FROM AUTHOR]

In the current paper, we have successfully synthesized three new mercury coordination polymers with fascinating structures and properties via a flexible sulfur donor ligand, namely, {[Hg(μ2-Cl)(μ2-Ls)]} n [BF4] n (1), {[Hg(μ2-Cl)(μ2-Ls)]} n [ClO4] n (2), and [Hg(SCN)2(μ2-Ls)] n (3) [Ls = 1,1-bis(3-methyl-4-imidazoline-2-thione)methane]. These complexes have been characterized by means of different techniques such as single crystal X-ray crystallography, FT-IR, elemental analysis (CHNS), UV-Vis, PXRD, BET, and TGA. Suitable single crystals of all complexes were obtained using the branch tube method with a very high yield and good stability due to the high affinity of mercury to bind to the thione groups. The cationic moieties of polymers 1 and 2 were isostructural, with a HgCl2S2 coordination core structure. The voids of the quasi-hexagonal packing of the columnar chains were occupied by unbonded tetrahedral BF4− ions in 1 and perchlorate anions in polymer 2. Polymer 3 has a less distorted tetrahedral geometry than 1 and 2, with a HgS4 core structure. By considering the thiophilicity of mercury, a thioamide-based Ls ligand was used to detoxify Hg(II) into insoluble polymers 1–3. The results of an MTT assay for (HepG2) liver cells confirmed the excellent cytoprotective effect of this ligand against mercury. Based on IC50 calculations, their toxicity was in order of polymer 1 > polymer 2 > polymer 3. These polymers were also considered as adsorbents for the reversible removal of iodine from solution and the kinetics of the process has been studied in detail. Interestingly, all of them showed an excellent stability and high capacity, in order of 763.53 mg g−1, 877.10 mg g−1, and 905.31 mg g−1 for polymers 1–3, respectively. [ABSTRACT FROM AUTHOR]

Nowadays, nitrogen rich compounds are the key research objects for high-energy materials. In this paper, a novel nitrogen rich energetic compound (NABTI) and its salt (4) with bis(tetrazole)imidazole as the skeleton were synthesized by simple steps. Their detailed structural data and stability parameters were obtained through experiments, and the internal relationship between them was theoretically analyzed. The results show that they both have regular planar configurations and layer-by-layer packing patterns, and the 3D hydrogen-bonding network and π–π interactions inside the crystals weaken their sensitivity to mechanical stimuli. As the most direct parameter reflecting the energy level, the detonation velocity (D) and detonation pressure (P) of the compounds in the study were calculated through the EXPLOV5 software package. The calculation results showed that NABTI exhibited a better detonation performance (D = 8329 m s−1 and P = 31.4 GPa) than the same type (triazole–tetrazole, NATT) of compound. The advantages of NABTI, such as high nitrogen content, high energy and simple synthesis, fully demonstrate its practicality. [ABSTRACT FROM AUTHOR]

In this study, a novel and highly efficient "turn-off" fluorescence imidazole-based sensor (BIB) with a symmetric structure was synthesized by a four-step reaction, from o-phenylenediamine, 6-bromo-2-pyridinecarboxaldehyde, and 1-bromohexane. The sensing mechanism was confirmed via fluorescence titration, HRMS, and 1HNMR techiniques. The results showed that the binding ratio of BIB and Ag+ was 1 : 1 in a DMF-HEPES (pH 7.4) solution (9 : 1, v/v). The fluorescence response of BIB exhibited a good linear response within the Ag+ concentration ranging from 2 × 10−7 to 8 × 10−6 mol L−1, and the limit of detection was calculated to be 4.591 × 10−8 mol L−1. BIB was successfully applied to the detection of Ag+ in water samples with recoveries of 97.25–109.50% and relative standard deviations (RSD) of 1.14–2.45%. In addition, BIB can successfully be applied to qualitatively and quantitatively identify Ag+ in water by test paper strips of BIB, which is fast and convenient. This provides a possible potential for the rapid monitoring of metal ions by sensors in environmental research. [ABSTRACT FROM AUTHOR]

Responsive photonic crystals have attracted extensive attention due to their features of transforming external stimuli into a variation of optical signals or structural colors. In recent years, the accumulation of heavy metal ions has become a serious threat to human health and the environment. Thus, a simple and rapid method for the accurate detection of metal ions is of great importance. Herein, an imidazole-based-silica inverse opal photonic crystal (IOPC) sensor is prepared. Three different particle sizes of SiO2 photonic crystals were used as templates for the preparation of an IOPC. The results show that the template presents a high specific surface area and interconnected nanopores. When the nanopores adsorb copper ions, the functional monomer imidazole will chelate with copper ions to form a flat quadrilateral structure. Then the nanopores of the IOPC shrink, which will result in the red shifting of the diffraction peak to complete the visual response sensing. When immersed in different concentrations of metal ions, the structural color of the IOPC changes, making it a visual sensor. In addition, it is proved that the imidazole-modified IOPC is specifically responsive to Cu2+, and the structural color of the sensor will shift from green to yellow after sensing. The detection limit is as low as 1 × 10−6 mol L−1, and the maximum offset of the diffraction peak can reach 50 nm. Therefore, the IOPC prepared here provides an ideal platform for the fast and high selective detection of Cu2+, and it has potential applications in the rapid detection of other heavy metal ions. [ABSTRACT FROM AUTHOR]