Yan-Xi Tan

Hybrid Zeolitic Imidazolate Frameworks with Catalytically Active TO4 Building Blocks

Crystalline porous materials with diverse chemical compositions (e.g., inorganic porous materials, inorganic–organic hybrid frameworks, and covalent organic frameworks) and framework topologies have been intensively studied in the past 60 years. They have wide applications in fields such as heterogeneous catalysis, gas storage, and separation. Moreover, some currently emerging areas related to health, energy use, and environmental conservation and remediation are still looking for the development of new porous materials. Zeolites are among the most well known porous materials because of their typical 4-connected open frameworks with TO4 (T= Si , Al, or P etc.) building blocks and outstanding catalytic or gas separation properties. Recently, the search for new zeolite-like structures was extended to metal–organic frameworks (MOFs), and these explorations in part produced a variety of zeolitic imidazolate frameworks (ZIFs) in which the tetrahedrally coordinated divalent cations (M=Zn or Co) are connected by the uninegative imidazolate ligands (im ). The rich chemistry associated with the organic imidazolate building blocks in ZIFs leads to some exceptional properties, such as large surface area and high gas uptake capacities. A question that emerges is: “Are there material with properties intermediate of those of zeolites and ZIFs?”. It is true that there is a hybrid state that remains unknown to date. In this work, we were seeking to integrate compositional and structural features of zeolites and ZIFs by combining TO4 tetrahedra with zinc–imidazolate units. Such a combination is trusted to bear both merits of zeolites and ZIFs, for example, possession of catalytic active TO4 sits of zeolites and high porosity of ZIFs. Herein, we report this kind of hybrid zeolitic imidazolate framework [denoted HZIFs; general formula: M4(im)6TO4] with catalytically active TO4 (T=Mo 6+ or W) building blocks and high thermal stability (up to 550 8C), which presents a new class of porous materials filling the gap between zeolites and ZIFs. The HZIFs reported herein are constructed from two kinds of tetrahedral building blocks and contain two kinds of connectivity, and combine structural features of both zeolites and ZIFs (Scheme 1). The TO4 units used in HZIFs are not traditional SiO4 or AlO4 units in aluminosilicate zeolites, but

Interrupted zeolite LTA and ATN-type boron imidazolate frameworks.

Zeolite A (LTA) is of much interest in zeolite family because of its large-scale industrial applications. Making Zeolite A (a typical 4-connected tetrahedral framework material) with a lower connectivity (3-connected) might lead to new open architecture with expanded ring size and enhanced functionality. The first interrupted Zeolite A with 3-connected network has been experimentally realized here by a boron imidazolate (im) framework material (BIF-20) with 3-coordinate BH(mim)(3)(-) building units. Additionally, a new strategy toward the construction of functional microporous metal-organic frameworks with interrupted zeolite-type topologies is presented by both 3-connected boron imidazolate frameworks (BIF-20 and BIF-21). BIF-20 has an unusual tetrahedral framework with both debonded α and β cages, and exhibits high H(2) uptake capacity.

Pore partition effect on gas sorption properties of an anionic metal–organic framework with exposed Cu2+ coordination sites

Presented here is an anionic nanoporous framework material with mobile guest cations which can perform ion exchanges with different tetraalkylammonium cations, and the resulting tunable pore structures exhibit interesting pore partition effects on gas storage and separation.

Gas sorption, second-order nonlinear optics, and luminescence properties of a series of lanthanide-organic frameworks based on nanosized tris((4-carboxyl)phenylduryl)amine ligand.

By controlling the pH value of the reaction system, two sets of lanthanide (Ln)-tris((4-carboxyl)phenylduryl)amine (Ln = Ce, Pr, Nd, Sm) frameworks have been generated. Four isostructural noninterpenetrating frameworks (FIR-8 to FIR-11) are constructed from rod-shaped secondary building units and four other isostructural frameworks (FIR-12 to FIR-15) based on single Ln nodes are described as 8-fold interpenetrating dia-type nets. Gas sorption measurements for FIR-8 give a Langmuir surface area of 633.8 m(2)·g(-1) and a H2 uptake of 165.2 cm(3)·g(-1) at 77 K and 1 atm. However, FIR-12 with smaller pores can hardly adsorb any N2 and H2. Because both FIR-8 and FIR-12 crystallize in acentric space group, the second-harmonic generation (SHG) measurements indicate that both of them display strong powder SHG efficiencies, which are approximately 8 and 3 times as strong as that of a potassium dihydrogen phosphate powder. In addition, the fluorescent emissions of all compounds in the solid state are also investigated in detail.

Microporous Zinc Tris[(4-carboxyl)phenylduryl]amine Framework with an Unusual Topological Net for Gas Storage and Separation

By employment of a new tris[(4-carboxyl)phenylduryl]amine ligand to assembly with the Zn(2+) ion, a new topological net built from four coordinatively linked ths nets is first evidenced in the 2-fold-interpenetrating framework FIR-1, which shows potential applications in gas storage and separation.

Highly Selective and Sensitive Trimethylamine Gas Sensor Based on Cobalt Imidazolate Framework Material

A cobalt imidazolate (im) framework material [Co(im)2]n was employed to use as a trimethylamine (TMA) gas sensor and the [Co(im)2]n sensor can be easily fabricated by using Ag-Pd interdigitated electrodes. Gas sensing measurement indicated that the [Co(im)2]n sensor shows excellent selectivity, high gas response and a low detection limit level of 2 ppm to TMA at 75 °C. The good selectivity and high response to TMA of the sensor based on [Co(im)2]n may be attributed to the weak interaction between the TMA molecules and the [Co(im)2]n framework. That may provide an ideal candidate for detecting freshness of fish and seafood.

Comparative study of activation methods on tuning gas sorption properties of a metal-organic framework with nanosized ligands.

Presented here is a new porous metal-organic framework based on a nanosized tris((4-carboxyl)phenylduryl)amine ligand, which features a 2-fold interpenetrating hms network and shows distinct gas adsorption behaviors dependent on different activation methods.

Guest inducing fluorescence switching in lanthanide–tris((4-carboxyl)phenylduryl)amine frameworks integrating porosity and flexibility

By employing the nanosized tris((4-carboxyl)phenylduryl)amine ligand to assemble with Ln3+ ions, a series of 2-fold interpenetrating lanthanide–organic frameworks (LnOFs; Ln = Y, Eu–Yb; FIR-16 to FIR-24) and heterometallic EuxTby–LnOFs (x + y = 2; FIR-25 to FIR-27) possessing the novel (3,6)-connected topology have been generated. FIR-17 with a high surface area of 941 m2 g−1 is an interesting flexible framework. Reversible fluorescence switching upon the presence or removal of guest molecules with different sizes is observed by using FIR-17 as a promising solvent sensor. This work presents an outstanding integration of photoluminescent properties and porosity for flexible lanthanide–organic frameworks.

Homochiral porous metal–organic frameworks containing only achiral building blocks for enantioselective separation

Enantioselective separation of racemic 1-phenethanol via hydrogen bonding interactions is realized in two enantiomorphous robust metal–organic frameworks (MOFs) with permanent porosity for high hydrogen uptake and reversible guest exchange function through a single-crystal-to-single-crystal fashion, which opens a new route toward enantioselective separation by employing low-cost homochiral MOFs containing only achiral building blocks.

A water-stable zeolite-like metal–organic framework for selective separation of organic dyes

Presented here is a water-stable zeolite-like metal–organic framework material AgIn(ina)4 (1; ina = isonicotinate) integrating two special tetrahedral building units ([AgN4]+ and [In(COO)4]−), which can rapidly adsorb methyl orange (MO) over methylene blue (MB) from water in 6 minutes and release MO in an easy way.