By Introducing Multiple Hydrogen Bonds Endows MOF Electrodes with an Enhanced Structural Stability.

Recently, metal-organic frameworks (MOFs) have attracted great interest in energy storage areas. However, the poor structural stability of MOFs derived from weak coordination bonds limits their applications. Here, quadruple hydrogen bonds (H-bonds) were introduced onto the MOFs to enhance their structural stability. Cross-linked networks could be formed between molecules owing to multiple H-bonds, strengthening the framework stability. Moreover, the dynamic reversibility of H-bonds could endow MOFs with self-healing ability. Furthermore, due to lower binding energy compared to coordination bonds, H-bonds break preferentially when subjected to internal stress, thus protecting the MOFs. Consequently, the as-prepared self-healing hybrid (SHH-Cu-MOF@Ti3C2TX) exhibited high capacitance retention (89.4%) after 5000 cycles at 1 A g-1, while that hybrid without dynamic H-bonds (H-Cu-MOF@Ti3C2TX) presented a 79.9% retention, delivering an enhancement in cycling stability. Moreover, an asymmetric supercapacitor (ASC) was fabricated by employing SHH-Cu-MOF@Ti3C2TX and activated carbon (AC) as the electrodes. The ASC delivered a specific capacitance (47.4 F g-1 at 1 A g-1), an energy density (16.9 Wh kg-1), and a power density (800 W kg-1) as well as good rate ability (retains 81% of its initial capacitance from 0.2 A g-1 to 5 A g-1).

Dual-State Fluorescent Probe for Ultrafast and Sensitive Detection of Nerve Agent Simulants in Solution and Vapor.

The development of fluorescent probes for detecting nerve agents has been the main concern focus of research because of their lethal toxicity for humans. Herein, a probe (PQSP) based on the quinoxalinone unit and the styrene pyridine group was synthesized and could visually detect a sarin simulant diethyl chlorophosphate (DCP) with excellent sensing properties in solution and solid states. Interestingly, PQSP showed an apparent intramolecular charge-transfer process by catalytic protonation after reacting with DCP in methanol, accompanied with the aggregation recombination effect. The sensing process was also verified by nuclear magnetic resonance spectra, scanning electron microscopy, and theoretical calculations. In addition, the papered test strips of loading probe PQSP exhibited an ultrafast response time within 3 s and high sensitivity with a limit of detection of 3 ppb for the detection of DCP vapor. Therefore, this research provides a designed strategy for developing the probes with dual-state emission fluorescence in solution and solid states for detecting DCP sensitively and rapidly, which can be fabricated as chemosensors to visually detect nerve agents in practice.

In Situ Synthesis of Hierarchical Porous Zr-MOFs on Columnar Activated Carbon and Application in Toxic Gas Adsorption.

Metal organic frameworks (MOFs) have been explored as adsorption materials owing to their diversity, controllable structure, high specific surface area, and abundant active sites. However, the shaping of MOFs has become a critical issue hindering their commercial application. A binder or high pressure is commonly used in traditional powder shaping, causing pores to be blocked or collapsed and porosity to be decreased, eventually leading to the degradation of adsorption performance. In this paper, Zr-MOFs were in situ grown on a columnar activated carbon (CAC) matrix, and a series of Zr-MOFs/CAC composites were prepared. The adsorption properties for SO2 and NO2 were measured by dynamic adsorption tests, and the Wheel-Jonas model was used to calculate the saturated adsorption capacity. Abundant mesopores can be formed between MOF crystals and activated carbon particles, and the mesoporosity of Zr-MOFs/CAC composites reached over 50%. Owing to the abundant mesoporous, increased activated sites as well as the synergistic effect between MOFs and activated carbon, the as-obtained HP-Zr-MOFs/CAC exhibited the best adsorption performance both for SO2 and NO2, which are 34.2 and 17.4 mg g-1, respectively, while the adsorption capacities of CAC for SO2 and NO2 are 20.9 and 6.6 mg g-1, respectively. The outstanding performance and facile synthesis process of HP-Zr-MOFs/CAC composites could provide ideas to develop other hierarchical porous MOFs/activated carbon composites.

Optimized NiCo2O4/rGO hybrid nanostructures on carbon fiber as an electrode for asymmetric supercapacitors.

The NiCo2O4 nanowires and reduced graphene oxide (rGO) hybrid nanostructure has been constructed on carbon fibers (NiCo2O4/rGO/CF) via a hydrothermal method. The effects of graphene oxide (GO) concentration on the structure and performance of the NiCo2O4/rGO/CF were investigated in detail to obtain the optimized electrode. When the GO concentration was 0.4 mg ml-1, the rGO/NiCo2O4/CF composite exhibited a maximum specific capacitance of 931.7 F g-1 at 1 A g-1, while that of NiCo2O4/CF was 704.9 F g-1. Furthermore, the NiCo2O4/rGO/CF//AC asymmetric supercapacitor with a maximum specific capacitance of 61.2 F g-1 at 1 A g-1 was fabricated, which delivered a maximum energy density (24.6 W h kg-1) and a maximum power density (8477.7 W kg-1). Results suggested that the NiCo2O4/rGO/CF composite would be a desirable electrode for flexible supercapacitors.

[Adsorption characteristics of acetone and butanone onto honeycomb ZSM-5 molecular sieve].

Adsorption capacity of acetone and acetone-butanone mixture onto honeycomb ZSM-5 molecular sieve was measured in this paper, and the influences of relative humidity, initial adsorbate concentration and airflow velocity on the adsorption process were investigated. Besides, adsorption performance parameters were calculated by Wheeler's equation. The results showed that relative humidity had no obvious influence on the acetone adsorption performance, which suggests that this material has good hydrophobic ability; in the low concentration range, the dynamic saturated adsorption capacity of acetone increased with the increase of initial concentration, but in the occasion of high concentration of acetone gas (more than 9 mg x L(-1)), the dynamic saturated adsorption capacity maintained at a certain level and did not vary with the increase of initial concentration; the increase of air flow velocity resulted in significant increase of acetone adsorption rate constant, at the same time the critical layer thickness of the adsorbent bed also increased significantly. In the cases of acetone-butanone mixture, the adsorption capacity of butanone onto ZSM-5 was clearly higher than that of acetone.