Bin Tan

Largest discrete supertetrahedral clusters synthesized in ionic liquids

Four discrete T5 cluster compounds with Cu–M–S constituents (M = In for compound 1, Ga for 2–4) have been synthesized in an ionic liquid (IL) [Bmmim]Cl (Bmmim = 1-butyl-2,3-dimethyl-imidazolium), which represent the largest molecular clusters in a Tn series. The in situ decomposition of the IL generates the Bim ligand (Bim = 1-butyl-2-methyl-imidazole) that directly coordinates to some of the corner Ga3+ ions of the T5 clusters in 3–4, leading to the formation of the first inorganic–organic hybrid T5 clusters. 2–4 show significantly broad photoluminescent emission bands ranging from 500 to 800 nm with a full width at half maximum (fwhm) at about 180 nm. This research provides a new method for synthesizing molecular metal chalcogenides that uses ILs as a reactive solvent and stabilizer.

A magnesium MOF as a sensitive fluorescence sensor for CS2 and nitroaromatic compounds

Presented here are the hydrothermal synthesis, structural characterization, and luminescent and gas adsorption properties of a magnesium metal–organic framework compound, namely Mg5(OH)2(BTEC)2(H2O)4·11H2O (1, H4BTEC = 1,2,4,5-benzenetetracarboxylic acid). The structure of 1 features a three-dimensional network constructed from the linkage of BTEC ligands and rare pentanuclear magnesium clusters as secondary building units, giving rise to the 1D channels along the a axis. Luminescence studies revealed that compound 1 demonstrated high fluorescence sensing of carbon disulfide (CS2) and nitroaromatic compounds, that is, the fluorescence intensities were almost completely quenched only at the concentrations of 0.8 vol% of CS2 and 0.04 vol% of nitrobenzene.

Ionothermal syntheses, crystal structures and properties of three-dimensional rare earth metal–organic frameworks with 1,4-naphthalenedicarboxylic acid

Twelve isostructural rare earth metal-organic frameworks, namely, [Hmim][RE(2)Cl(1,4-NDC)(3)] (RE = La (1), Ce (2), Pr (3), Nd (4), Sm (5), Eu (6), Gd (7), Tb (8), Dy (9), Ho (10), Er (11), Y (12), Hmim = 1-hexyl-3-methylimidazolium, 1,4-NDCH(2) = 1,4-naphthalenedicarboxylic acid), have been ionothermally synthesized and structurally characterized. The structures feature three-dimensionally anionic frameworks of [RE(2)Cl(1,4-NDC)(3)](n)(n-) with channels in which the Hmim(+) cations are located. The current results are the first ionothermal synthesis of rare earth metal-organic frameworks based on 1,4-NDCH(2) which possess a previously unknown (4,7)-connected 3-nodal network with the Schläfli symbol of (3(2)·4(2)·5(2))(3(2)·4(9)·5(2)·6(8))(2)(4(3)·6(3))(2). Luminescent and magnetic properties of some of the title compounds have been studied. Thermogravimetric analyses indicated that all these compounds were thermally stable up to ca. 250 °C.

Introduction of lewis acidic and redox-active sites into a porous framework for ammonia capture with visual color response.

Based on the Lewis acidic site and redox ability of bipyridinium ligand, a porous framework with an adsorption advantage for ammonia over water and color response ability has been constructed. The compound is highly stable and flexible to external stimuli, exhibiting reversible single-crystal-to-single-crystal transformations, in response to temperature change and NH3 capture. More attractively, the title compound shows obvious color change from yellow to dark blue when exposed to ammonia vapor within just a few seconds, indicating a strong ability to function as a visual colorimetric absorbent for ammonia.

Polycatenation‐Driven Self‐Assembly of Nanoporous Frameworks Based on a 1D Ribbon of Rings: Regular Structural Evolution, Interpenetration Transformation, and Photochemical Modification

A series of nanoporous frameworks constructed by a polycatenated isoreticular 1D ribbon of rings have been developed. The orientation of catenated ribbons can be fine tuned by varying counter anions, which allows both pore size and shape to be systematically adjusted in a pre-synthetic process. Distinct from conventional pore construction modes in which the organic linkers are alternately connected by metal nodes into a 3D periodic arrangement, the present polycatenation approach represents an alternative for constructing soft porous materials with tunable pore metrics and functions. Furthermore, these porous structures can interconvert into each other based on an anion-exchange process, accompanied by the transformation of the interpenetrating structures in different dimensional networks, which is unusual in porous frameworks. In addition, such a porous framework can be post-synthetically modified by a photoinduced [2+2] cycloaddition reaction, which not only achieves the surface modification (from conjugated to non-conjugated inner surface), but also triggers the structural transformation from low dimension to high dimension. Such a post-modification process reinforces the pore architecture through a covalent locking effect and has a great impact on the adsorption properties.

Anion-induced structural transformation involving interpenetration control and luminescence switching

Three metal–organic coordination compounds with different interpenetrating modes, [Cd(BCbpy)(BDC)]·3H2O (1), [Cd2(BCbpy)2(BDC)Cl2][Cd(BCbpy)2(BDC)]·18H2O (2), and [Cd(BCbpy)Cl2]·3H2O (3) (HBCbpyCl = 1-(4-carboxybenzyl)-4,4-bipyridinium chloride, H2BDC = 1,4-benzenedicarboxylic acid), have been synthesized and structurally characterized. Compound 1 exhibits a 2D + 2D → 2D interpenetrating array with the coexistence of polyrotaxane and polycatenane structures. Compound 2 is an unprecedented example of a 2D + 2D + 1D → 2D interpenetrating structure which involves 2D + 2D → 2D parallel interpenetration and a 2D + 1D → 2D polyrotaxane. In the case of compound 3, the absence of the rod-like BDC ligand prevents threading through the ring-like units, no polyrotaxane structure is formed, and the compound features infinite 1D ring-containing chains arranged in parallel without any interpenetration. Interestingly, the structural transformation can be achieved through a solvent-mediated anion exchange process when compound 1 or 2 is exposed to the aqueous solution containing chloride ions. Upon progressive replacement of the BDC2− ligands by chloride ions, the complicated network topology is simplified and undergoes an evolution from interpenetration to non-interpenetration, accompanied by a visually observed on–off–on fluorescence switching.

π-Conjugation-directed highly selective adsorption of benzene over cyclohexane

Crystalline materials with large tailor-made channels have been made by an isoreticular synthesis strategy, which includes a successful adjustment of the π-conjugation over a framework skeleton allowing target recognition for aromatic molecules. The selective absorption of benzene over cyclohexane has been achieved, with a significant increase in benzene uptake with the improvement of the degree of π-conjugation.

Dual-Emission Luminescence of Magnesium Coordination Polymers Based on Mixed Organic Ligands.

Presented herein are two luminescent magnesium coordination polymers (Mg-CPs), namely [Mg2 (H2O)2 (2-NDC)4 (1,10-phen)2] (1) and [Mg2 (H2O)(1,4-NDC)2 (1,10-phen)] (2), in which 2-NDCH=2-naphthalenecarboxylic acid, 1,4-NDCH2 =1,4-naphthalene dicarboxylic acid, and 1,10-phen=1,10-phenanthroline. Based on the mixed ligands, the title compounds exhibit linker-based photoluminescence (PL) properties thanks to the unique configuration of the Mg(2+) ions. The two compounds show interesting dual emission on excitation of the different luminophores of the mixed linkers. In particular, the emissions of compound 2 could be tuned from green to yellow simply by varying the excitation energies. Furthermore, 2 could be excited by using a commercial λ=450 nm blue LED chip to generate white-light emission, which allows the fabrication of a white-light-emitting diode (WLED) with 20 lm W(-1) luminous efficacy. This work may provide a new method for designing tunable PL CPs by using the low-cost and abundant magnesium ion.

Targeted Functionalization of Porous Materials for Separation of Alcohol/Water Mixtures by Modular Assembly

Three isoreticular hydrogen-bonded frameworks with functionalized pore structures were constructed by a modular self-assembly process in which a series of amino acids with various substituents serve as facile exchange subassemblies to decorate the pore wall. The ordered amino acid side-chain groups in the pore channels play an important role in determining the adsorption behavior of the framework materials, and ensure exclusive adsorption of methanol/water over ethanol. Gas-chromatographic separation experiments demonstrated that alcohols can be efficiently separated from ternary water/methanol/ethanol mixtures and revealed a key influence of the adsorbate-host framework interaction on the practical separation performance of mixtures.

A photoactive porous metal–organic complex: synthesis, crystal morphology and the influence of photocycloaddition on fluorescence properties and adsorption behavior

A photoactive porous metal–organic complex has been constructed based on an olefin-containing pyridinium derivative, 1-(3-carboxybenzyl)-4-[2-(4-pyridyl)-vinyl]-pyridinium chloride (m-HBCbpe·Cl). The double bond in the BCbpe ligand has been successfully aligned in a photoactive orientation through cation–π interactions, thus enabling the complex to undergo a photochemical [2 + 2] cycloaddition reaction in 100% yield upon UV-light irradiation. Sudden cracking of the crystal can be observed during this process. Interestingly, photocycloaddition not only induces fluorescence switching from no luminescence to strong yellow luminescence emission under UV light, but also triggers a structural change which has a significant impact on CO2 adsorption.