Ai-Xin Zhu

Strong and Dynamic CO2 Sorption in a Flexible Porous Framework Possessing Guest Chelating Claws

Using a bis-triazolate ligand and tetrahedral Zn(II) ion, we synthesized a flexible porous coordination polymer functionalized with pairs of uncoordinated triazolate N-donors that can be used as guest chelating sites to give very high CO(2) adsorption enthalpy and CO(2)/N(2) selectivity. The dynamic CO(2) sorption behavior could be monitored well by single-crystal X-ray diffraction.

Pore Surface Tailored SOD‐Type Metal‐Organic Zeolites

Natural and synthetic zeolites are important microporous materials. [ 1 ] The highly ordered structures and tunable compositions of aluminosilicate frameworks are responsible for their extraordinary performances. After the discovery of zeolitic metal imidazolate frameworks, ranging from zeolite-like cobalt imidazolates [ 2 ] to the SOD-, ANA-, and RHO-type (three-letter codes of zeolite topologies) zinc benziimidazolate [ 3 ] and 2-alkylimidazolates, [ 4 ] these novel porous coordination polymers (PCPs) have blossomed in the past few years. [ 5 ] The similarity of the bended exo-bidentate coordination mode of imidazolate with that of the O atom in aluminosilicates has been considered as a determinative construction principle ( Figure 1 ). The rich structure-directing role of imidazolate side groups provides an additional variable for enumeration of new zeolitic structures. [ 3–5 ] Nevertheless, there seems to be some inherent difference between the inorganic and metal-organic counterparts. For example, inorganic zeolites are negatively charged aluminosilicate frameworks and their pore surface property can be routinely tailored by adjusting the Al/Si ratio and/or cation exchange. In contrast, PCPs (including metal-organic zeolites) are well-known to be completely ordered materials. Among the large family of known metal-organic zeolites, SOD-[Zn(mim) 2 ] (Hmim = 2-methylimidazole [ 4 ] ) is noteworthy for its high porosity and exceptional stability. The synthesis, porous property, sorption mechanism, and application of MAF-4 (the metal azolate framework 4) have attracted much attention. [ 6 ] However, MAF-4 only adsorbs many important gases, such as H 2 , CO 2 , and C 2 H 2 weakly, due to the lack of a strong adsorption site on its pore surface. While new functionalities of MAF-4 are still emerging, efforts have been devoted to the structural modifi cation of this prototype framework. Because imidazolates are almost the shortest linkers in PCPs, variation of the metal ion and/or substituent groups on the imidazolate linker can largely alter porosity (size or volume), change the framework, [ 5e–h ] and even alter the whole network topology. Metal ion substitution can effectively change the pore surface properties of PCPs functionalized with coordinatively unsaturated metal centers. [ 7 ] However, the tetrahedral

Isomeric Zinc(II) Triazolate Frameworks with 3-Connected Networks : Syntheses, Structures, and Sorption Properties

Two pairs of supramolecular isomers based on ternary zinc(II)/triazolate/X (triazolate = 3,5-dimethyl-1,2,4-triazolate (Hdmtz), X = HCOO(-), F(-)) metal azolate frameworks, namely, [Zn(dmtz)(HCOO)] x H(2)O (MAF-X3, 1a), [Zn(dmtz)(HCOO)] x (1/6Me(2)NH)(1/4H(2)O) (MAF-X4, 1b), [Zn(dmtz)F] (MAF-X5, 2a), and [Zn(dmtz)F] (MAF-X6, 2b), have been synthesized via variations of the reaction conditions. The 3-connected Zn(dmtz) networks in 1a, 1b, 2a, and 2b can be described as rarely observed 4.8(2), 4.12(2), (8,3)-b, and 8(2).10-a, respectively. Besides the mu(3)-dmtz, tetrahedral and trigonal-bipyramidal/square-pyramidal coordination of the Zn ions are accomplished by monodentate formate and mu-F, respectively. While 1a and 2b are nonporous structures, 1b and 2a exhibits 1D nanotubular hydrophilic (d 3.2 A) and hydrophobic (d 3.6 A) channels, respectively. Thermogravimetric analysis shows that the stabilities of 2a and 2b are much better than those of 1a and 1b, which may be ascribed to different coordination numbers of zinc atoms. Moreover, 1b and 2a with different pore properties show selective sorption behavior.

Self-catalysed aerobic oxidization of organic linker in porous crystal for on-demand regulation of sorption behaviours.

Control over the structure and property of synthetic materials is crucial for practical applications. Here we report a facile, green and controllable solid-gas reaction strategy for on-demand modification of porous coordination polymer. Copper(I) and a methylene-bridged bis-triazolate ligand are combined to construct a porous crystal consisting of both enzyme-like O2-activation site and oxidizable organic substrate. Thermogravimetry, single-crystal X-ray diffraction, electron paramagnetic resonance and infrared spectroscopy showed that the methylene groups can be oxidized by O2/air even at room temperature via formation of the highly active Cu(II)-O2(˙-) intermediate, to form carbonyl groups with enhance rigidity and polarity, without destroying the copper(I) triazolate framework. Since the oxidation degree or reaction progress can be easily monitored by the change of sample weight, gas sorption property of the crystal can be continuously and drastically (up to 4 orders of magnitude) tuned to give very high and even invertible selectivity for CO2, CH4 and C2H6.

Pentanuclear and Heptanuclear Helicates By Self-Assembly of d10 Metal Ions and a Rigid Aromatic Bis-Bidentate Chelator

The self-assembly of Zn(II) and Cd(II) ions with a bis-bidentate ligand 3,5-bis(benzimidazol-2-yl)pyrazole (H 3L) was studied by Electrospray ionization mass spectrometry, (1)H NMR measurements, and single-crystal X-ray diffraction analyses. Reaction of Zn(ClO 4) 2.6H 2O and Cd(ClO 4) 2.6H 2O with H 3L in DMF gave two pentanuclear complexes [(Zn 5(mu 3-O)(H 2L) 6)(ClO 4) 2.DMF.9.5H 2O ( 1) and [Cd 5(mu 3-O)(H 2L) 6](ClO 4)(OH).4.75DMF.0.25EtOH.10.5H 2O ( 2), in which the trigonal-bipyramidal core structures are bridged by mu 3-oxo and pyrazolate rings of the monodeprotonated H 2L. When Na 3PO 4.12H 2O was used in the reaction system of CdBr 2.4H 2O and H 3L, [Cd 5(mu 3-O)(H 2L) 6]Br 2.4.5DMF.6.5H 2O ( 3) and [Cd 7(mu 6-PO 4)(mu-Br) 3(H 2L) 6](HPO 4).DMF.10H 2O ( 4) were isolated. 3 displays the same core structure as that of 2, whereas 4 exhibits a turbinate, heptanuclear core which is bridged by a mu 6-PO 4, three mu-Br, and three pyrazolate rings. All of the pentanuclear and heptanuclear cores are surrounded by three pairs of bis-bidentate H 2L (-) ligands with offset pi-pi stacking, showing propeller-like molecular structures and triple-stand helicates. Electrospray ionization mass spectrometry studies and (1)H NMR measurements demonstrate that the pentanuclear complexes have different stability in the solution, depending on the metal ions and the counteranions. Furthermore, both 1 and 2 emit blue fluorescence with nanosecond luminescent lifetimes in DMF at room temperature.

Single-crystal X-ray diffraction and Raman spectroscopy studies of isobaric N2 adsorption in SOD-type metal–organic zeolites

The two-step N(2) adsorption behaviour of sodalite-type Zn(II) 2-methylimidazolate and 3-methyl-1,2,4-triazolate has been comprehensively and accurately elucidated.

A luminescent cadmium(II) metal–organic framework based on a triazolate–carboxylate ligand exhibiting selective gas adsorption and guest-dependent photoluminescence properties

A luminescent cadmium metal–organic framework functionalized with uncoordinated triazolate N-donors has been constructed by using a triazolate–carboxylate bifunctional organic ligand. It exhibits selective adsorption of CO2 over N2 behavior, and interesting guest-dependent photoluminescence properties.

A series of Zn(II) and Cd(II) coordination compounds based on 4-(4H-1,2,4-triazol-4-yl)benzoic acid: synthesis, structure and photoluminescence properties

Seven coordination compounds, namely [Zn(4-tba)2(H2O)2] (1), [Zn(4-tba)Cl]·CH3OH (2), [Zn(4-tba)2] (3), [Zn(4-tba)2]·DMA·3.5H2O (4), [Cd(4-tba)2]·DMF·3.6H2O (5), [Cd(4-tba)2] (6) and [Cd5Cl4(4-tba)6]·1.5DMF·4H2O (7) (4-Htba = 4-(4H-1,2,4-triazol-4-yl)benzoic acid, DMA = N,N-dimethylacetamide and DMF = N,N-dimethylformamide), have been synthesized under hydro/solvothermal conditions by using a triazolate–carboxylate bifunctional organic ligand, 4-Htba. Complexes 1 and 2 exhibit a mononuclear motif and a two-dimensional (2D) network with sql topology, respectively, whereas 3–6 display different interpenetrating structures. Compound 3 shows a 2-fold interpenetrating 2D net with sql topology, 4 and 5 display uninodal 4-connected 4-fold interpenetrating 3D nets with dia (66) topology belonging to class Ia and class IIIa, respectively, and compound 6 exhibits a 5-fold interpenetrating dia net. Complex 7 exhibits a non-interpenetrating 3D framework constructed from decanuclear cadmium–chloride chain units and 4-tba ligands with various coordination modes. All the complexes were characterized using single-crystal X-ray diffraction, powder X-ray diffraction (PXRD), IR spectroscopy and elemental analyses. In addition, the thermogravimetric analysis and solid-state photoluminescence results for 1–7 were also investigated.

Two luminescent lanthanide–organic frameworks containing bithiophene groups for the selective detection of nitrobenzene and Fe3+

Two lanthanide–organic frameworks formulated as [Eu2(DMTDC)3(DEF)4]·DEF·6H2O (1) and [Tb2(DMTDC)3(DEF)4]·DEF·6H2O (2) (H2DMTDC = 3,4-dimethylthieno[2,3-b]thiophene-2,5-dicarboxylic acid and DEF = N,N-diethylformamide) have been synthesized under solvothermal conditions by using a bithiophene dicarboxylate organic ligand, H2DMTDC. Compounds 1 and 2 are isomorphous and feature 3D frameworks with uninodal six-connected pcu α-Po topology structures. The systematic luminescence experiments reveal that 1 and 2 can be used as fast-response fluorescence sensors for the sensitive detection of nitrobenzene and Fe3+ ions with favorable recyclability through fluorescence quenching.

Retraction: Chemical etching of a cobalt-based metal–organic framework for enhancing the electrocatalytic oxygen evolution reaction

Retraction of ‘Chemical etching of a cobalt-based metal–organic framework for enhancing the electrocatalytic oxygen evolution reaction’ by Ai-Xin Zhu et al., J. Mater. Chem. A, 2017, DOI: 10.1039/c7ta02103h.