Metal‐Triflate‐Catalyzed Synthesis of Polycyclic Tertiary Alcohols by Cyclization of γ‐Allenic Ketones

It has been established that bismuth(III) triflate catalyzes the cyclization of γ‐allenic ketones under mild reaction conditions. This reaction allows the selective formation of polycyclic tertiary alcohols from cyclic ketone derivatives. The resulting dienols can engage in stereoselective cycloadditions to efficiently afford complex polycyclic systems.     

A Novel Bismuth‐Based Metal–Organic Framework for High Volumetric Methane and Carbon Dioxide Adsorption

Solvothermal reaction of H₄L (L=biphenyl‐3,3′,5,5′‐tetracarboxylate) and Bi(NO₃)₃ ? (H₂O)₅ in a mixture of DMF/MeCN/H₂O in the presence of piperazine and nitric acid at 100 °C for 10 h affords the solvated metal–organic polymer [Bi₂(L)_1.5(H₂O)₂] ? (DMF)_3.5 ? (H₂O)₃ (NOTT‐220‐solv). A single crystal X‐ray structure determination confirms that it crystallises in space group P2/c and has a neutral and non‐interpenetrated structure comprising binuclear {Bi₂} centres bridged by tetracarboxylate ligands. NOTT‐220‐solv shows a 3,6‐connected network having a framework topology with a {4 ? 6²}₂{4² ? 6⁵ ? 8⁸}{6² ? 8} point symbol. The desolvated material NOTT‐220a shows exceptionally high adsorption uptakes for CH₄ and CO₂ on a volumetric basis at moderate pressures and temperatures with a CO₂ uptake of 553 g L^?1 (20 bar, 293 K) with a saturation uptake of 688 g L^?1 (1 bar, 195 K). The corresponding CH₄ uptake was measured as 165 V(STP)/V (20 bar, 293 K) and 189 V(STP/V) (35 bar, 293 K) with a maximum CH₄ uptake for NOTT‐220a recorded at 20 bar and 195 K to be 287 V(STP)/V, while H₂ uptake of NOTT‐220a at 20 bar, 77 K is 42 g L^?1. These gas uptakes have been modelled by grand canonical Monte Carlo (GCMC) and density functional theory (DFT) calculations, which confirm the experimental data and give insights into the nature of the binding sites of CH₄ and CO₂ in this porous hybrid material.     

分析测试经验介绍(243~248)原子荧光法测定金矿中砷和铋的不确定度评估

通过建立数学模型,分析了原子荧光法测定金矿中砷和铋的测量不确定度的影响因素,计算各影响因素的不确定度分量,并计算金矿中砷和铋的合成标准不确定度和扩展不确定度.结果表明:测量不确定度主要由样品制备过程和标准曲线拟合构成.金矿中砷的含量为18.398μg/g,其扩展不确定度为0.555 3μg/g(k=2),结果符合测试规范要求.铋的含量为0.359 3μg/g,扩展不确定度为0.441 1μg/g(k=2),铋的不确定度偏大,不符合测试规范要求,应通过降低铋标准溶液的浓度和减少待测液的稀释倍数来降低标准曲线拟合产生的不确定度.     

纳米结构钛酸盐电极快速测定水体COD

分析了纳米结构钛酸盐电极快速测定COD的基本原理及COD标准物质定值方法。通过对纳米结构钛酸盐表征分析,钠型钛酸盐电极具有较高的灵敏度,外加0.7 V工作电位,测定COD溶液标准物质的线性相关系数大于0.995,误差在±8%以内;与国标方法比较,测量同一水样的误差在±15%以内。纳米结构钛酸盐电极可用于测量水体COD。     

Metal–Organic Framework-Derived Carbon Nanorods Encapsulating Bismuth Oxides for Rapid and Selective CO2 Electroreduction to Formate

Carbon dioxide (CO₂) conversion is promising in alleviating the excessive CO₂ level and simultaneously producing valuables. This work reports the preparation of carbon nanorods encapsulated bismuth oxides for the efficient CO₂ electroconversion toward formate production. This resultant catalyst exhibits a small onset potential of −0.28 V vs. RHE and partial current density of over 200 mA cm⁻² with a stable and high Faradaic efficiency of 93 % for formate generation in a flow cell configuration. Electrochemical results demonstrate the synergistic effect in the Bi₂O₃@C promotes the rapid and selective CO₂ reduction in which the Bi₂O₃ is beneficial for improving the reaction kinetics and formate selectivity, while the carbon matrix would be helpful for enhancing the activity and current density of formate production. This work provides effective bismuth-based MOF derivatives for efficient formate production and offers insights in promoting practical CO₂ conversion technology.     

Molten-Salt-Assisted Synthesis of Bismuth Nanosheets for Long-term Continuous Electrocatalytic Conversion of CO2 to Formate

Two-dimensional (2D) monometallic pnictogens (antimony or Sb, and bismuth or Bi) nanosheets demonstrate potential in a variety of fields, including quantum devices, catalysis, biomedicine and energy, because of their unique physical, chemical, electronic and optical properties. However, the development of general and high-efficiency preparative routes toward high-quality pnictogen nanosheets is challenging. A general method involving a molten-salt-assisted aluminothermic reduction process is reported for the synthesis of Sb and Bi nanosheets in high yields (>90 %). Electrocatalytic CO₂ reduction was investigated on the Bi nanosheets, and high catalytic selectively to formate was demonstrated with a considerable current density at a low overpotential and an impressive stability. Bi nanosheets continuously convert CO₂ into formate in a flow cell operating for one month, with a yield rate of 787.5 mmol cm⁻² h⁻¹. Theoretical results suggest that the edge sites of Bi are far more active than the terrace sites.     

(NH4)Bi2(IO3)2F5: An Unusual Ammonium‐Containing Metal Iodate Fluoride Showing Strong Second Harmonic Generation Response and Thermochromic Behavior

An ammonium‐containing metal iodate fluoride compound, (NH₄)Bi₂(IO₃)₂F₅, featuring a two‐dimensional double‐layered framework constructed by [BiO₂F₅]^6? and [BiO₄F₄]^9? polyhedra, as well as [IO₃]^? groups, was successfully synthesized. The well‐ordered alignment of these SHG‐active units leads to an extraordinary strong SHG response of 9.2 times that of KDP. Moreover, this compound possesses a large birefringence (Δn=0.0690 at 589.3 nm), a wide energy band gap (E_g=3.88 eV), and a high laser damage threshold (LDT; 40.2×AgGaS₂). In particular, thermochromic behavior was observed for the first time in this type of compound. Such multifunctional crystals will expand the application of nonlinear optical materials.     

Towards Long‐Term Photostability of Nickel Hydroxide/BiVO4 Photoanodes for Oxygen Evolution Catalysts via In Situ Catalyst Tuning

Increasing long‐term photostability of BiVO₄ photoelectrode is an important issue for solar water splitting. The NiOOH oxygen evolution catalyst (OEC) has fast water oxidation kinetics compared to the FeOOH OEC. However, it generally shows a lower photoresponse and poor stability because of the more substantial interface recombination at the NiOOH/BiVO₄ junction. Herein, we utilize a plasma etching approach to reduce both interface/surface recombination at NiOOH/BiVO₄ and NiOOH/electrolyte junctions. Further, adding Fe²⁺ into the borate buffer electrolyte alleviates the active but unstable character of etched‐NiOOH/BiVO₄, leading to an outstanding oxygen evolution over 200 h. The improved charge transfer and photostability can be attributed to the active defects and a mixture of NiOOH/NiO/Ni in OEC induced by plasma etching. Metallic Ni acts as the ion source for the in situ generation of the NiFe OEC over long‐term durability.