[en] A novel porous anionic metal–organic framework, (Me_2NH_2)_2[Zn_2L_1_._5bpy]·2DMF (BUT-201; H_4L=4,8-disulfonaphthalene-2,6-dicarboxylic acid; bpy=4,4-bipyridine; DMF=N,N-dimethylformamide), with pillared double-layer structure has been synthesized through the reaction of a sulfonated carboxylic acid ligand and Zn(NO_3)_2·6H_2O with 4,4-bipyridine as a co-ligand. It is found that BUT-201 can rapidly adsorb cationic dyes with a smaller size such as Methylene Blue (MB) and Acriflavine Hydrochloride (AH) by substitution of guest (CH_3)_2NH_2"+, but has no adsorption towards the cationic dyes with a lager size such as Methylene Violet (MV), the anionic dyes like C. I. Acid Yellow 1 (AY1) and neutral dyes like C. I. Solvent Yellow 7 (SY7), respectively. The results show that the adsorption behavior of BUT-201 relates not only to the charge but also to the size/shape of dyes. Furthermore, the adsorbed dyes can be gradually released in the methanol solution of LiNO_3. - Graphical abstract: A porous anionic metal–organic framework (BUT-201) can selectively adsorb the cationic dyes by cationic guest molecule substitution, and the adsorbed dyes can be gradually released in the methanol solution of LiNO_3. - Highlights: • An anionic metal-organic framework (BUT-201) has been synthesized and characterized. • BUT-201 has a three-dimensional (3D) pillared double-layer structure. • BUT-201 can selectively and rapidly adsorb cationic dyes. • The adsorbed dyes can be gradually released in the methanol solution of LiNO_3.

[en] RF breakdown is a common phenomenon in high-power RF devices. It may make irreversible damage to physical structure. Finding a sensitive method to detect the phenomenon and to cut-off RF power as quickly as possible is a good way to prevent the RF breakdown damage. This paper presents a digital and multi-function high-power RF protection system based on VSWR (Voltage Standing Wave Ratio) measurement. The response time of this system is about 700 ns, which includes 300 ns for klystron delay and path delay. The system provides a series of functions that meet the requirements of pulsed and long running accelerators. It also supports real-time graphical display and data recording, which is useful for fault analysis.

[en] This paper develops a modified Tait equation of state (EOS) for trans-decahydronaphthalene with four parameters A, B, V₀ and P₀ being treated as linear functions of temperature. The coefficients contained in these functions are determined through fitting the experimental compression data in the literature between 293 K and 446 K and at pressures from 10 to 200 MPa. Expressions for the thermal expansivity, isothermal compressibility and thermodynamic quantities are deduced and the numerical results are analytically derived. The numerical results show that the precision of the modified Tait EOS developed in this paper is superior to the EOS in the literature

[en] Highlights: • A bimetallic MOF directed strategy is proposed for fabricating Pt-doping heterojunctions. • Porous Pt-ZnO-Co₃O₄, Pt-ZnS-CoS, and Pt-Zn₃P₂-CoP heterojunction photocatalysts are made. • They exhibit excellent catalytic activity towards hydrogen generation from water splitting. Porous Pt-doping heterojunctions, Pt-ZnO-Co₃O₄, Pt-ZnS-CoS, and Pt-Zn₃P₂-CoP were fabricated by firstly the oxidation, sulfurization, and phosphorization of ZnCo-zeolitic-imidazolate-framework (ZnCo-ZIF) and then the doping of Pt nanoparticles. They exhibit excellent photocatalytic activity towards hydrogen generation from water splitting. These bimetallic metal-organic-framework (MOF) derivatives maintain the porous framework skeleton of ZnCo-ZIF precursor, there by significantly enhancing the light utilization and simultaneously affording abundant exposed catalytic active sites. Most importantly, suitable band matching and strong electron coupling in these heterojunctions are achieved by using the bimetallic MOF template, which facilitate the efficient electron-hole separation and transportation. In addition, Pt nanoparticles distributed on the porous heterojunctions as electron traps can offer rich redox active sites for the hydrogen generation. Correspondingly, the hydrogen generation rate of Pt-ZnO-Co₃O₄, Pt-ZnS-CoS, and Pt-Zn₃P₂-CoP was up to ~7.80, ~8.21, and ~9.15 mmol h⁻¹ g⁻¹, respectively, higher than those of respective ZIF-8 or ZIF-67-based derivatives. This work thus provides a new approach that using bimetallic MOF as template directs the fabrication of noble-metal doping heterojunctions to simultaneously enhance light absorption utilization, electro-hole separation, and transport, therefore promoting surface water oxidation reaction for efficient water splitting.

[en] Further development of metal-organic frameworks (MOFs) requires an establishment of hierarchical interaction within the framework. Herein, we report a series of mesoporous rare-earth (RE) MOFs that are constructed from an unusual 12-connected $\mathrm{\pi <!--\; ??\; -->}$-stacked pyrene secondary building unit (SBU) and a typical 12-connected RE${}_6$ cluster (RE=Eu, Y, Yb, Tb, Ce). The judicious design of a butterfly-shape pyrene ligand with a tert-butyl substituent enables the formation of the disordered 12-connected organic SBUs on its strong intermolecular π-π interactions. The assembly of 12-connected inorganic cuboctahedron SBUs and 12-connected organic distorted hexagonal prism SBUs generates an unprecedented network that can be further simplified into a 4,4-connected pts net linked from planar square and tetrahedra. This work provides fresh insights into the design and synthesis of frameworks constructed from coordinatively, covalently, and noncovalently linked building units. (© 2020 Wiley‐VCH GmbH)

[en] A metal organic framework (MOF) based adsorbent of type UiO-66 was hydrothermally prepared and applied to simultaneous sensing and removal of the asthma drug clenbuterol. The MOF possesses a large specific surface area (1460 cm²·g⁻¹) and a stable structure, and has a large adsorption capacity for clenbuterol (160 mg·g⁻¹). If clenbuterol binds to the MOF, the fluorescence of the sorbent (best measured at excitation/emission wavelengths of 290/396 nm) is quenched by up to 88%. Based on these findings, a fluorometric assay has been developed for the rapid determination of clenbuterol. The adsorption equilibrium of UiO-66 for CLB can be achieved at 60 min and the adsorption efficiency is above 80%. The method has a linear response in the 4.0 to 40 ng·mL⁻¹ concentration range, and the lower limit of detection is 0.17 μM. All of this indicates that UiO-66 is promising for simultaneous detection and the removal of CLB in water.

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[en] A chemically stable Zr(IV)-based metal-organic framework (BUT-17) has been explored for simultaneous adsorption and determination of bisphenol compounds (BPs) in aqueous medium. The prepared BUT-17 possesses a large surface area (2936 m² g⁻¹) and excellent fluorescent performance. An adsorption capacity of 111 mg g⁻¹ for bisphenol A (BPA) with a rapid adsorption rate (1.76 g mg⁻¹ min⁻¹) is achieved by BUT-17. The excellent adsorption performance could be attributed to the hydrogen bond interaction between BPs and BUT-17. Furthermore, the fluorescent intensity of BUT-17 was quenched up to 92% due to the formation of complexes between BPs and BUT-17. Thus, a BUT-17-based fluorescent sensing method for the rapid determination of BPs has been established with the limit of detection of 10.0 ng mL⁻¹ for BPA and a linear range from 2.0 to 23.0 μg mL⁻¹. These results indicate that as an outstanding multifunctional platform, BUT-17 is promising for the simultaneous removal and determination of BPs in water medium. Graphical abstract:

[en] Exploitation of new metal–organic framework (MOF) materials with high surface areas has been attracting great attention in related research communities due to their broad potential applications. In this work, a new Zr(IV)-based MOF, [Zr_6O_4(OH)_4(eddb)_6] (BUT-30, H_2eddb=4,4′-(ethyne-1,2-diyl)dibenzoic acid) has been solvothermally synthesized, characterized, and explored for gases and dyes adsorptions. Single-crystal X-ray diffraction analysis demonstrates a three-dimensional cubic framework structure of this MOF, in which each Zr_6O_4(OH)_4 building unit is linked by 12 linear eddb ligands. BUT-30 has been found stable up to 400 °C and has a Brunauer–Emmett–Teller (BET) surface area as high as 3940.6 m"2 g"−"1 (based on the N_2 adsorption at 77 K) and total pore volume of 1.55 cm"3 g"−"1. It is more interesting that this MOF exhibits stepwise adsorption behaviors for Ar, N_2, and CO_2 at low temperatures, and selective uptakes towards different ionic dyes. - Graphical abstract: A new Zr(IV)-based MOF with high surface area has been synthesized and structurally characterized, which shows stepwise gas adsorption at low temperature and selective dye uptake from solution. - Highlights: • A new Zr-based MOF was synthesized and structurally characterized. • This MOF shows a higher surface area compared with its analogous UiO-67 and 68. • This MOF shows a rare stepwise adsorption towards light gases at low temperature. • This MOF performs selective uptakes towards cationic dyes over anionic ones. • Using triple-bond spacer is confirmed feasible in enhancing MOF surface areas

[en] Graphical abstract: - Highlights: • We develop a new DGT device for in situ sampling Cr (VI) in water. • Polyquaternary ammonium salt (PQAS) was used as binding agent of DGT device. • Cr (VI) can be accumulated in the PQAS binding phase whereas Cr (III) cannot. • The DGT performance was independent of pH 3–12 and ionic strength 1 × 10⁻³–1 mol L⁻¹. - Abstract: A diffusive gradients in thin films (DGT) device with polyquaternary ammonium salt (PQAS) as a novel binding agent (PQAS DGT) combined with graphite furnace atomic absorption spectrometry (GFAAS) was developed for the selective sampling and measurement of Cr (VI) in water. The performance of PQAS DGT was independent of pH 3–12 and ionic strength from 1 × 10⁻³ to 1 mol L⁻¹. DGT validation experiments showed that Cr (VI) was measured accurately as well as selectively by PQAS DGT, whereas Cr (III) was not determined quantitatively. Compared with diphenylcarbazide spectrophotometric method (DPC), the measurement of Cr (VI) with PQAS DGT was agreement with that of DPC method in the industrial wastewater. PQAS-DGT device had been successfully deployed in local freshwater. The concentrations of Cr (VI) determined by PQAS DGT coupled with GFAAS in Nuer River, Ling River and North Lake were 0.73 ± 0.09 μg L⁻¹, 0.50 ± 0.07 μg L⁻¹ and 0.61 ± 0.07 μg L⁻¹, respectively. The results indicate that PQAS DGT device can be used for the selective sampling and measurement Cr (VI) in water and its detection limit is lower than that of DPC method

[en] Highlights: • Mn-Cu bimetallic catalysts were facilely prepared by one-step hydrothermal-redox method. • Hydrothermal-redox was superior to other preparation methods for Mn-Cu catalysts. • MnCu spinel type catalyst exhibited excellent low-temperature catalytic performance. • PTR-MS results revealed the reaction routes of toluene oxidation over MnCu catalyst. Developing facile preparation method to obtain the satisfied low-temperature catalytic performance of transitional metal oxide-based materials is still a challenge in deep degradation of VOCs. Here, a series of Mn-Cu bimetallic oxide catalysts were prepared by one-step hydrothermal-redox method for catalytic total oxidation of toluene. The CH₃COOH concentration, Cu/Mn molar ratio and calcination temperature greatly affected the crystal structure, micromorphology and catalytic performance. Amongst, MnCu spinel structured catalyst exhibited excellent low-temperature catalytic activity, superior durability and water resistance in toluene total oxidation owing to its abundant surface adsorbed oxygen species, higher amount of Cu⁺ and Mn³⁺ and excellent low-temperature reducibility. The reaction rate of MnCu was 7.0 times higher than that of MnCu_0.5 at 210 °C. The cyclic redox process with enough oxygen vacancy played a vital role in toluene oxidation. The deep oxidation of benzene was the key step in the toluene oxidation. Proton transfer reaction-mass spectrometry (PTR-MS) results revealed the reaction intermediates including benzaldehyde, benzene and phenol, which further decomposed to acetone, ethanol, acetic acid, ketone and acetaldehyde by ring opening before total mineralization. Therefore, PTR-MS provided a facile method to investigate the reaction mechanism of toluene oxidation.