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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]

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]

Zeolitic imidazolate frameworks (ZIFs) have attracted considerable attention for many potential applications because they have a unique porous structure and excellent thermal and chemical stabilities. In recent years, significant efforts have been made to develop different methods for the controllable synthesis of ZIFs with desirable crystal structure and morphologies, and for decreasing the excessive amounts of organic ligands and solvents used in the synthesis process to reduce the costs and environmental impacts. This paper highlights the strategies recently reported, including the controllable synthesis of ZIFs with desirable morphologies and pore structure using a surfactant and a template in aqueous solution, the synthesis of ZIF particles and nanocrystals in base solution, and the dry gel and mechanochemical syntheses of ZIFs with minimal solvent usage. [ABSTRACT FROM AUTHOR]

A new series of uranium organophosphinates has been hydrothermally synthesized by using hydroxymethyl phenylphosphinic acid (HMPPA, HL) in the presence of imidazole derivatives, namely, UO2(L)2 (HMPP-U1), (UO2)2(L)4(dib) (HMPP-U2), (UO2)2(L)2(ox)(dib) (HMPP-U3), (Hbpi)2[(UO2)4(L)6(ox)2] (HMPP-U4) and (UO2)2(L)2(ox)(bpbi)2 (HMPP-U5) (ox = oxalate, dib = 1,4-di(1H-imidazol-1-yl)benzene, bpi = 1-(biphenyl-4-yl)-1H-imidazole, bpbi = 1-([1,1'-biphenyl]-4-yl)-1H-benzo[d]imidazole). HMPP-U1 was directly synthesized through hydrothermal reaction between HMPPA and UO22+, featuring a single chain structure constructed from sole UO6 tetragonal bipyramids bridged by HMPP ligands. With further introduction of imidazole derivatives, a layered structure of HMPP-U2 is formed, in which dib molecules are coordinated to uranyl centers as bidentate coligands. By adding glycol into the synthesis, a common dimeric building unit is isolated, which comprises two U-centered pentagonal bipyramids linked by an in situ generated oxalate group. In HMPP-U3, a one-dimensional structure comprising such dimeric uranyl entities and HMPP ligands is pillared by dib, forming a layered assembly. HMPP-U4 incorporates the dimeric uranyl units connected by HMPP ligands, leading to a two-dimensional arrangement with bpi as the template. HMPP-U5 features a one-dimensional structure composed of the uranyl dimers and HMPP ligands. The bpbi molecules serving as coligands are coordinated to the chain. The syntheses and structures as well as the correlations and discrepancies of these uranyl organophosphinates are discussed in this paper. [ABSTRACT FROM AUTHOR]