Ben Xu

Fluorescence turn-on detection of uric acid by a water-stable metal–organic nanotube with high selectivity and sensitivity

Herein we provide a new strategy for fluorescence detection of uric acid (UA) using a metal–organic nanotube of CD-MONT-2 for the first time. This novel fluorescent probe exhibits high selectivity and sensitivity for UA with a very good detection limit of 4.3 μM. The results of density functional theory calculations and 1H NMR spectra show that the turn-on sensing mechanism arises from the host–guest interactions of capsule-like CD-MONT-2 with UA to result in electron transfer between UA and CD-MONT-2′. Furthermore, CD-MONT-2′ exhibits very fast adsorption of UA molecules in aqueous solution as confirmed by UV-Vis spectra and HPLC analysis, making it a potential candidate for application in the removal of UA from the human blood.

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.

Pore‐Environment Engineering with Multiple Metal Sites in Rare‐Earth Porphyrinic Metal–Organic Frameworks

Multi-component metal-organic frameworks (MOFs) with precisely controlled pore environments are highly desired owing to their potential applications in gas adsorption, separation, cooperative catalysis, and biomimetics. A series of multi-component MOFs, namely PCN-900(RE), were constructed from a combination of tetratopic porphyrinic linkers, linear linkers, and rare-earth hexanuclear clusters (RE6 ) under the guidance of thermodynamics. These MOFs exhibit high surface areas (up to 2523 cm2  g-1 ) and unlimited tunability by modification of metal nodes and/or linker components. Post-synthetic exchange of linear linkers and metalation of two organic linkers were realized, allowing the incorporation of a wide range of functional moieties. Two different metal sites were sequentially placed on the linear linker and the tetratopic porphyrinic linker, respectively, giving rise to an ideal platform for heterogeneous catalysis.

A MOF-derived coral-like NiSe@NC nanohybrid: an efficient electrocatalyst for the hydrogen evolution reaction at all pH values

A coral-like NiSe@NC nanohybrid as an effective electrocatalyst for the hydrogen evolution reaction (HER) at all pH values, constructed via the in situ selenation of a Ni-MOFs precursor, is reported. The electrocatalyst shows overpotentials of 123 mV, 250 mV and 300 mV in 0.5 M H2SO4, 1.0 M KOH and 1.0 M PBS, respectively, to afford a current density of 10 mA cm-2. Meanwhile, NiSe@NC also exhibits a small Tafel slope and superior long-term stability over a wide pH range. The excellent electrocatalytic performance should be ascribed to the unique coral-like structure with a large BET specific surface area (125.4 m2 g-1) and mesoporous features, as well as synergistic effects between NiSe nanocrystals and highly conductive N-doped porous carbon.

Bimetallic-MOF Derived Accordion-like Ternary Composite for High-Performance Supercapacitors

Supercapacitors are regarded to be highly probable candidates for next-generation energy storage devices. Herein, a bimetallic Co/Ni MOF is used as a sacrificial template through an alkaline hydrolysis and selective oxidation process to prepare an accordion-like ternary NiCo2O4/β-Ni xCo1- x(OH)2/α-Ni xCo1- x(OH)2 composite, which is composed of Co/Ni(OH)2 nanosheets with large specific surface as the frame and NiCo2O4 nanoparticles with high conductivity as the insertion, for supercapacitor application. This material exhibits both high specific capacitance (1315 F·g-1 at 5 A·g-1) and excellent cycle performance (retained 90.7% after 10 000 cycles). This hydrolysis-oxidation process, alkali hydrolysis followed by oxidation with H2O2, offers a novel approach to fabricate the Ni/Co-based electrode materials with enhanced supercapacitor performance.

Optimizing crystallinity and porosity of hierarchical Ni(OH)2 through conformal transformation of metal–organic framework template for supercapacitor applications

MOFs (metal–organic frameworks) are widely utilized as both the templates and precursors to prepare nanomaterials as supercapacitor electrodes. However, traditional thermolysis routes are difficult to control and usually lead to collapse of the MOF skeletons, which hinders wider applications. Herein, we describe a simple and facile strategy for fabricating the Ni(OH)2 hierarchical structure by the “conformal transformation” of one particular Ni-MOF through hydrolysis in the KOH aqueous solution. By controlling the concentration of KOH solution and the soaking time, the obtained Ni(OH)2 nanomaterial possesses both optimized crystallinity and porosity, extremely beneficial for electron transportation and ion migration within the electrodes. Taking these advantages, the Ni(OH)2 electrode presents a remarkable specific capacity of 830.6 C g−1, and the fabricated all-solid state asymmetric supercapacitor presents a remarkable energy density of 37.8 W h kg−1 at a power density of 252.67 W kg−1, which surpasses most Ni(OH)2 based supercapacitor devices. After 15 000 cycles, the capacitance remains at over 93% of the initial value.