Rui-Qin Zhong

A Porous Metal−Organic Replica of α-PbO2 for Capture of Nerve Agent Surrogate

A novel metal-organic replica of α-PbO(2) exhibits high capacity for capture of nerve agent surrogate.

Improved Hydrogen Release from Ammonia–Borane with ZIF-8

The promotion for hydrogen release from ammonia-borane (AB) was observed in the presence of ZIF-8. Even at concentrations of ZIF-8 as low as 0.25 mol %, a reduction of the onset temperature for dehydrogenation accompanies an increase in both the rate and amount of hydrogen released from AB.

Selective adsorption of CO2/CH4 and CO2/N2 within a charged metal–organic framework

Presented here is a new ultramicroporous metal–organic framework (MOF) formulated as [Zn3L2(HCOO)1.5][(CH3)2NH2]1.5·xDMF, 1 (H3L = 9-(4-carboxy-phenyl)-9H-carbazole-3,6-dicarboxylic acid), DMF = N,N-dimethylformamide, consisting of an anionic framework and two types of interlaced one-dimensional channels with 0.42 and 0.79 nm diameters respectively, in which the larger channels accommodate protonated dimethylamine as the counter cations. Gas sorption analysis of N2, CO2 and CH4 was investigated and the isotherms exhibit reversible thermodynamic behaviours without hysteresis desorption, evidencing framework rigidity and permanent porosity of solvent-free 1. The synergistic effect of the open ultramicropores and dimethylamine cations may lead to high efficiency separation of CO2 from CH4 and N2. According to the Toth model, the selectivity of CO2/CH4 and CO2/N2 was calculated to be 96 and 37, respectively. This effort will give rise to a new conception to tailor the charged MOF for high efficiency CO2 adsorption and separation.

Metal–organic coordination architectures with 3-pyridin-3-yl-benzoate: crystal structures, fluorescent emission and magnetic properties

Reactions of 3-pyridin-3-yl-benzoic acid (HL) with metal nitrates under hydrothermal conditions yield seven new coordination polymers: Ni(L)2(H2O)2 (1), [Ni(L)2](H2O) (2), Co(L)2(H2O)2 (3), [Zn(L)2](H2O) (4), Cu(L)2 (5), Cd(L)2 (6) and Gd2(L)6(H2O)4 (7). A systematic investigation on coordination chemistry of the ligand and the significant function of supramolecular interactions in managing the resultant crystalline networks has been carried out. On the basis of the X-ray diffraction analysis of these complexes, the results show that complexes 1–5 and 7 form similar one-dimensional (1D) double-chain coordination arrays, among which 1 and 3, as well as 2 and 4, are isostructural. Remarkably, distinct network architectures are further constructed with the aid of weak secondary interactions. Amongst them, complexes 1, 3 and 5 exhibit the classical α-polonium networks, while complexes 2 and 4 present the (3,4)-connected two-dimensional layers. In 7, the intermolecular π–π stacking interactions lead to the formation of a double-strand structure. The CdII complex 6 assembles into a three-dimensional metal–organic framework exhibiting a unique 6-connected roa topology. The trans-configuration of L ligand is only found in the case of 6, whereas the cis-ligands are generally observed in these complexes. The fluorescent emission properties of 4 and 6 as well as the magnetic property of 7 have also been investigated.

Observation of helical water chains reversibly inlayed in magnesium imidazole-4,5-dicarboxylate

A helical water chain, reversibly inlayed in a magnesium imidazole-4,5-dicarboxlylate, was characterized by single-crystal X-ray diffraction, thermogravimetric analysis, as well as temperature-variable Fourier transform infrared spectroscopy and powder X-ray diffraction techniques.

Solvent-induced deviation in square-grid layers of microporous Cu(II) isophthalates: layer stacking and gas adsorption properties

Solvothermal reactions of Cu(II) nitrate with isophthalic acid (H2IPT) in various solvents create five novel metal coordination polymers, [Cu(IPT)(H2O)](H2O)2 (1), Cu(IPT)(C2H5OH) (2), Cu2(IPT)2(DEF)(H2O) (3) (DEF = N,N′-diethylformamide), [Cu4(IPT)4(DMF)2(C2H5OH)(H2O)](DMF)2 (4) (DMF = N,N′-dimethylformamide), and [Cu2(IPT)2(CH3CN)(H2O)](H2O)2.25 (5), respectively. Structural analyses exhibit that they all form 2D non-interpenetrated square-grid layers based on paddle-wheel Cu2clusters as nodes and isophthalate as linkers, in which various guest molecules are trapped via either the coordination to open Lewis acid copper sites or inclusion in open channels. The different chemical affinities of the 2D square-grid layers toward various solvent molecules result in guest-induced deviation of these 2D layers and diverse porosities in their frameworks, as realized by the distinct gas adsorption properties.

Physical, structural, and dehydrogenation properties of ammonia borane in ionic liquids

Ionic liquids (ILs) are excellent solvents for the dehydrogenation of ammonia borane (AB); however, the basic properties that allow efficient dehydrogenation are still unclear. In this report, density, viscosity, melting/freezing/glass transition temperature, solubility, and the dehydrogenation properties, including impurity gas quantification, of AB-imidazolium-based IL solutions were studied. Note that ILs can solubilize 32–35 wt% of AB, and the liquid AB–IL solutions have densities of ∼0.9 g cm−3, viscosities similar to motor oil (100–250 cP), and glass transition temperatures below −50 °C. AB–ILs are stable at room temperature for several weeks with minimal hydrogen generation, although some hydrolysis occurs immediately upon mixing as a result of trace water content. Between 80 and 130 °C, more than 2 mol H2/AB are desorbed from AB–ILs with limited impurity emissions. Furthermore, there is no reaction between AB and ILs upon dehydrogenation, and structural analysis reveals a complex solid solution.

Lanthanide contraction effects on the structures, thermostabilities, and CO2 adsorption and separation behaviors of isostructural lanthanide–organic frameworks

A systematic investigation of the CO2 adsorption and separation behaviours of fourteen isostructural lanthanide–organic frameworks (LOFs) of lanthanide benzenetricarboxylate (LnBTC) is executed, where Ln = Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm and Yb. These LOFs are facilely synthesized and randomly scaled by heating a mixture of 1,3,5-benzenetricarboxylic acid and lanthanide nitrate solution with reaction time less than 1 h. Structure refinement reveals that these LOFs exhibit three-dimensional networks with one-dimensional channels and open metal sites on the pore walls. Thermogravimetric analyses verify that these LOFs are stable up to 540 °C. Influenced by the opposing effects of ionic radius and molecular mass from Y(III)–Yb(III), the LOFs with the highest CO2 uptakes are YBTC at 273 K and PrBTC at 298 K at atmospheric pressure. Moreover, the real CO2 separation from binary gas mixtures of CO2–N2 and CO2–CH4 further indicates that the lanthanide contraction plays the most important role in tuning the adsorption and separation performance of the resulting materials. This work may give rise to the potential application of highly thermostable porous LOF materials in carbon dioxide capture from flue gas and natural gas, in order to reduce greenhouse emissions and improve energy efficiency.

Self-preservation and structural transition of gas hydrates during dissociation below the ice point: an in situ study using Raman spectroscopy

The hydrate structure type and dissociation behavior for pure methane and methane-ethane hydrates at temperatures below the ice point and atmospheric pressure were investigated using in situ Raman spectroscopic analysis. The self-preservation effect of sI methane hydrate is significant at lower temperatures (268.15 to 270.15 K), as determined by the stable C-H region Raman peaks and AL/AS value (Ratio of total peak area corresponding to occupancies of guest molecules in large cavities to small cavities) being around 3.0. However, it was reduced at higher temperatures (271.15 K and 272.15 K), as shown from the dramatic change in Raman spectra and fluctuations in AL/AS values. The self-preservation effect for methane-ethane double hydrate is observed at temperatures lower than 271.15 K. The structure transition from sI to sII occurred during the methane-ethane hydrate decomposition process, which was clearly identified by the shift in peak positions and the change in relative peak intensities at temperatures from 269.15 K to 271.15 K. Further investigation shows that the selectivity for self-preservation of methane over ethane leads to the structure transition; this kind of selectivity increases with decreasing temperature. This work provides new insight into the kinetic behavior of hydrate dissociation below the ice point.

Experimental and theoretical investigation of a stable zinc-based metal–organic framework for CO2 removal from syngas

A stable Zn-based metal–organic framework has been synthesized and applied for CO2 removal from syngas composed of CO and H2 for the first time. Further study using the combination of Monte Carlo simulation and ideal adsorbed solution theory method demonstrates the CO2 adsorption behavior and separation performance which have been further confirmed by breakthrough experiments.