Zixi Kang

Metal–organic frameworks based luminescent materials for nitroaromatics sensing

Metal–organic frameworks (MOFs), composed of organic ligands and metal nodes, are well known for their high and permanent porosity, crystalline nature and versatile potential applications, which promoted them to be one of the most rapidly developing research focuses in chemical and materials science. During the various applications of MOFs, the photoluminescence properties of MOFs have received growing attention, especially for nitroaromatics (NACs) sensing, due to the consideration of homeland security, environmental cleaning and military issues. In this highlight, we summarize the progress in recent research in NACs sensing based on LMOFs cataloged by sensing techniques in the past three years, and then we describe the sensing applications for nano-MOF type materials and MOF film, together with MOF film applications.

Recent advances and challenges of metal–organic framework membranes for gas separation

Gas separation is one of the most critical and challenging steps for industrial processes, and metal–organic framework (MOF) membranes are potential candidates for this application. This review mainly focuses on the recent advances in improving the performance of MOF membranes, involving the issues faced with MOF designation and growth for practical applications. First, we discussed three strategies for permeability and selectivity enhancement of MOF membranes, in terms of obtaining ultra-thin two-dimensional (2D) MOF nanosheets, fine-tuning the pore size of the MOF framework and integrating with other species. Second, we reviewed the recent potential resolutions to the problems of MOF membranes for future practical applications including scale-up preparation and stability improvement. Finally, we summarized our work by providing some general conclusions on the state-of-the-art and an outlook on some development directions of molecule-sieving membranes.

Tuning the Dimensionality of Interpenetration in a Pair of Framework-Catenation Isomers To Achieve Selective Adsorption of CO2 and Fluorescent Sensing of Metal Ions

A pair of framework-catenation isomers (UPC-19 and UPC-20) based on an anthracene-functionality dicarboxylate ligand were synthesized and characterized for the first time through tuning of the dimensionality of interpenetration. The interpenetration dimensionality significantly influences the properties including the porosity, gas-uptake capacity, and fluorescent sensing ability: UPC-19 with 5-fold interpenetration is nonporous, whereas the 3-fold interpenetration form of UPC-20 is porous and exhibits selective adsorption of CO2 and fluorescent sensing of Cu(2+) and Fe(3+) through fluorescence quenching.

Green Fabrication of Ultrathin Co3O4 Nanosheets from Metal–Organic Framework for Robust High-Rate Supercapacitors

Two-dimensional cobalt oxide (Co3O4) is a promising candidate for robust electrochemical capacitors with high performance. Herein, we use 2,3,5,6-tetramethyl-1,4-diisophthalate as a recyclable ligand to construct a Co-based metal-organic framework of UPC-9, and subsequently, we obtain ultrathin hierarchical Co3O4 hexagonal nanosheets with a thickness of 3.5 nm through a hydrolysis and calcination process. A remarkable and excellent specific capacitance of 1121 F·g-1 at a current density of 1 A·g-1 and 873 F·g-1 at a current density of 25 A·g-1 were achieved for the as-prepared asymmetric supercapacitor, which can be attributed to the ultrathin 2D morphology and the rich macroporous and mesoporous structures of the ultrathin Co3O4 nanosheets. This synthesis strategy is environmentally benign and economically viable due to the fact that the costly organic ligand molecules are recycled, reducing the materials cost as well as the environmental cost for the synthesis process.

Solvent modulated assembly of two Zn metal–organic frameworks: syntheses, luminescence, and gas adsorption properties

A 2D wave-like layered framework based on benzotriazole-5-carboxylic acid (H2btca), 2,2′-bipy and zinc ions – [Zn(btca)(2,2′-bipy)]n (1) – has been resoundingly designed and synthesized by a solvothermal method. By changing the solvent from DMF to DMA, a 3D porous framework – [Zn2(btca)2(bpy)(H2O)]n·n(DMA) (2) – was obtained. Complexes 1 and 2 have been determined by single-crystal X-ray diffraction analysis and further characterized by powder X-ray diffraction (PXRD), elemental analysis, IR spectroscopy, and thermogravimetric (TG) analysis. Complex 1 shows an AA packing 2D layered structure and complex 2 displays a 3D open honeycomb framework with a (3,4)-connected 2-nodal fsc topology. Moreover, gas adsorption of 2a (the activated form of 2) and the luminescence properties of 1, 2 and 2a have also been investigated intensively.

In situ confinement of free linkers within a stable MOF membrane for highly improved gas separation properties

A stable MOF membrane with guest molecules encapsulated in the pores by in situ synthesis has been successfully fabricated. The in situ confinement of linkers in the channels of the MOF membrane improves its gas separation properties, which may provide a general method for fine-tuning the pore size of MOF membranes and develop the functional applications of porous MOF materials.

A yolk–shelled Co9S8/MoS2–CN nanocomposite derived from a metal–organic framework as a high performance anode for sodium ion batteries

Sodium-ion batteries (SIBs) are considered as a promising energy storage device, and anode materials are proved to essentially affect their electrochemical performance. In this work, a yolk–shell structured Co9S8/MoS2 polyhedron with N-doped carbon composite (Co9S8/MoS2–CN) was designed and synthesized through a step by step process using ZIF-67 as the precursor. And this composite is demonstrated to be an excellent electrode candidate material for SIBs due to the magnificent yolk–shelled structures, in situ CN coating and the synergistic effect of the binary sulfides. The Co9S8/MoS2–CN composite electrode shows highly stable cycling performance and delivers a reversible discharge capacity of 438 mA h g−1 within 150 cycles at a current density of 1.0 A g−1, which is much higher than that of Co9S8–CN or MoS2 electrodes. Even at a high current density of 2.0 A g−1, it can also deliver an impressively stable capacity of 421 mA h g−1 within 250 cycles.

In situ generation of intercalated membranes for efficient gas separation

Membranes with well-defined pore structure which have thin active layers may be promising materials for efficient gas separation. Graphene oxide (GO) materials have potential applications in the field of membrane separation. Here we describe a strategy for the construction of ultra-thin and flexible HKUST-1@GO intercalated membranes, where HKUST-1 is a copper-based metal–organic framework with coordinatively unsaturated metal sites, with simultaneous and synergistic modulation of permeance and selectivity to achieve high H2/CO2 separation. CuO nanosheets@GO membranes are fabricated layer-by-layer via repeated filtration cycles, then transformed to HKUST-1@GO membranes upon in situ reaction with linkers. The HKUST-1@GO membranes show enhanced performance for gas separation of H2/CO2 mixture. The number of filtration cycles is optimized to obtain H2 permeance of 5.77 × 10−7 mol m−2 s−1 Pa−1 and H2/CO2 selectivity of 73.2. Our work provides a facile strategy for the construction of membranes based on metal–organic frameworks and GO, which may be applied in the preparation of flexible membranes for gas separation applications.Graphene oxide membranes are promising materials for the separation of low molecular weight gases. Here, composite membranes comprising metal organic frameworks and graphene oxide show improved selectivity for the separation of hydrogen and carbon dioxide over graphene oxide alone.