Single-Atom Iron Catalysts on Overhang-Eave Carbon Cages for High-Performance Oxygen Reduction Reaction

Single-atom catalysts have drawn great attention, especially in electrocatalysis. However, most of previous works focus on the enhanced catalytic properties via improving metal loading. Engineering morphologies of catalysts to facilitate mass transport through catalyst layers, thus increasing the utilization of each active site, is regarded as an appealing way for enhanced performance. Herein, we design an overhang-eave structure decorated with isolated single-atom iron sites via a silica-mediated MOF-templated approach for oxygen reduction reaction (ORR) catalysis. This catalyst demonstrates superior ORR performance in both alkaline and acidic electrolytes, comparable to the state-of-the-art Pt/C catalyst and superior to most precious-metal-free catalysts reported to date. This activity originates from its edge-rich structure, having more three-phase boundaries with enhanced mass transport of reactants to accessible single-atom iron sites (increasing the utilization of active sites), which verifies the practicability of such a synthetic approach.     

Ultrafast Encapsulation of Metal Nanoclusters into MFI Zeolite in the Course of Its Crystallization: Catalytic Application for Propane Dehydrogenation

Encapsulating metal nanoclusters into zeolites combines the superior catalytic activity of the nanoclusters with high stability and unique shape selectivity of the crystalline microporous materials. The preparation of such bifunctional catalysts, however, is often restricted by the mismatching in time scale between the fast formation of nanoclusters and the slow crystallization of zeolites. We herein demonstrate a novel strategy to overcome the mismatching issue, in which the crystallization of zeolites is expedited so as to synchronize it with the rapid formation of nanoclusters. The concept was demonstrated by confining Pt and Sn nanoclusters into a ZSM-5 (MFI) zeolite in the course of its crystallization, leading to an ultrafast, in situ encapsulation within just 5 min. The Pt/Sn-ZSM-5 exhibited exceptional activity and selectivity with stability in the dehydrogenation of propane to propene. This method of ultrafast encapsulation opens up a new avenue for designing and synthesizing composite zeolitic materials with structural and compositional complexity.     

A Layered Cationic Aluminum Oxyhydroxide as a Highly Efficient and Selective Trap for Heavy Metal Oxyanions

Cationic framework materials, especially pure inorganic cationic frameworks that can efficiently and selectively capture harmful heavy metal oxyanions from aqueous solution are highly desired yet scarcely reported. Herein, we report the discovery of a 2D cationic aluminum oxyhydroxide, JU-111, which sets a new benchmark for heavy metal oxyanion sorbents, especially for Cr^VI. Its structure was solved based on 3D electron diffraction tomography data. JU-111 shows fast sorption kinetics (ca. 20 min), high capture capacity (105.4 mg g⁻¹), and broad working pH range (3–10) toward Cr^VI oxyanions. Unlike layered double hydroxides (LDHs), which are poorly selective in the presence of CO₃²⁻, JU-111 retains excellent selectivity for Cr^VI even under a large excess of CO₃²⁻. These superior features coupled with the ultra-low cost and environmentally benign nature make JU-111 a promising candidate for toxic metal oxyanion remediation as well as other potential applications.     

具有抗生物污染活性的分子筛膜用于高效油水分离

The development of the global economy has been accompanied by frequent oil spills caused by accidental leaks and industrial manufacturing, which have seriously threatened the aquatic environment and human health. Traditional methods for the treatment of oily wastewater include centrifugation, skimming, flotation, oil-absorbing technology, etc., which are limited by low separation efficiency as well as secondary pollution during the post-processing of oil absorption materials. Recently, separation technologies utilizing the special wettabilities of filtration membranes have been developed to enrich and recycle oils from wastewater. Among these, the fabrication of superhydrophilic/underwater superhydrophobic membranes have attracted intensive research interest, which can selectively allow the passage of water through the membrane while blocking the oils. However, microorganisms are more likely to breed on these hydrophilic surfaces, eventually leading to the blockage of the membranes. In this study, ZSM-5 zeolite crystals (MFI topological structure) were coated onto the stainless-steel meshes by means of seeding and secondary hydrothermal growth. Then, 70% of the total Na⁺ ions in the zeolite channels were substituted by Ag⁺ ions via an ion exchange process. The resultant membranes (Ag@ZCMFs) were superamphiphilic in air, with both water contact angle and oil contact angle of approximately 0°. However, they became superoleophobic when immersed in water, and the underwater oil contact angle reached 151.27° ± 4.34°. In terms of special wettability, Ag@ZCMF achieved efficient separation for various oil-water mixtures with separation efficiencies above 99%. The water flux and intrusion pressure of Ag@ZCMF depended on the diameter of pinholes in the membrane, which could be modulated by altering the time of secondary hydrothermal growth. For instance, the average diameter of pinholes in Ag@ZCMF with optimum secondary growth time of 14 h (Ag@ZCMF-14) reached approximately 21 μm, giving rise to the water flux and intrusion pressure of 54720 L·m^-2·h^-1 and 4357 Pa, respectively. The anti-corrosion test and rubbing test confirmed the high chemical and mechanical stability of Ag@ZCMF-14, respectively. The separation efficiency of Ag@ZCMF-14 remained stable during ten purification-regeneration cycles, and no obvious attenuation was observed, proving the high separation stability of Ag@ZCMF-14. Furthermore, the loaded Ag⁺ ions afforded the membrane excellent anti-biofouling activity, which could effectively inhibit the growth of both alga and bacteria in the operating environment, thus preventing membrane blockage during the oil-water separation process. In particular, the bacteriostatic rate of Ag@ZCMF-14 to Escherichia coli reached to 99.6%. These results demonstrate that Ag@ZCMFs with anti-biofouling activity has promising potential future applications in the removal of oil slicks from oily wastewater.     

电控聚合物分散液晶变焦全息透镜制作

介绍了相位型全息聚合物分散液晶(PDLC)材料全息透镜,在电场作用下液晶微滴折射率逐渐与聚合物折射率匹配,实现透镜电控变焦。研究了微米尺寸和纳米尺寸液晶微滴聚合物分散液晶材料配方特性和微观结构。采用优化纳米尺寸材料配方制作5~6μm聚合物分散液晶盒,采用离轴式平面波和球面波干涉全息写入光路,成功制作电控变焦聚合物分散液晶全息透镜样品。该透镜样品焦距为20 mm,能够正一级衍射放大成像。实现“0”,“1”变焦的驱动电压阈值为60 V。并进一步提出了基于聚合物分散液晶电控变焦元件集成叠加技术实现电控变焦光学成像系统的技术思路。     

湍流大气传输中跟踪抖动对远场影响的仿真研究

分析了跟踪抖动对湍流大气传输远场光斑的影响。基于麦克斯韦电磁场理论,采用大气相干长度对大气湍流进行描述,推导了发射光束因跟踪抖动导致光轴偏离的远场表达式。在此基础上,利用相位屏法模拟抖动引起的倾斜相位和大气折射率起伏引起的相位调制,并采用低频补偿的功率谱反演法对传输过程进行了数值仿真。分析了不同跟踪抖动、湍流强度条件下远场光斑质心脱靶量的变化,以及不同尺寸模拟目标的回波概率。分析结果表明,在传输距离为10 km时,强湍流造成的远场光斑脱靶量可达几十μrad;当跟踪抖动较大时,湍流强弱对脱靶量影响差别很小。最后,对一定尺寸的模拟目标,从探测回波概率的角度给出了发射系统跟踪抖动量的控制范围。     

人工神经网络研究进展及其在光谱分析中的应用

介绍最常用的人工神经网络——BP神经网络的原理、结构及其研究进展,评述了人工神经网络在光谱分析中的应用。     

参数优化的最优性及在控制问题中的一个应用

在Banach空间中,给出了含参数的单值映射的不变类凸,拟不变类凸和伪不变类凸的概念.在这类较弱凸性条件下,提出了参数优化问题弱有效解的几个最优性充分条件.作为应用,研究了一类状态约束最优控制问题的弱最优控制.     

A Germanate Compound Constructed from Dissymmetric Ge7 Chains and Metal Complexes

Abstract. A novel germanate compound, |[Ni(dien)₂]₃(H₂O)₃|[Ge₇O₁₃F₅]₂(designated JU‐85, dien = diethylenetriamine), was solvothermally synthesized. The structure of JU‐85 was determined by single‐crystal X‐ray diffraction and further characterized by powder X‐ray diffraction, inductively coupled plasma, infrared spectroscopy, elemental analysis, and thermogravimetric analysis. JU‐85 has dissymmetric chains constructed from diagonally linked Ge₇ building units and various Ni(dien)₂²⁺ complexes formed in situ during the synthesis. Compared with its structural analogue, FJ‐6, JU‐85 contains less complex cations and different host‐guest assembly. Besides the diagonal linkage in JU‐85, other dissymmetric linkages of Ge₇ building units were enumerated, which could be used as the stereogenic centers for the design of novel chiral germanate compounds.     

弱碱性离子交换树脂在柠檬酸提炼中的应用

本文选用多种弱碱性阴离子交换树脂，去除柠檬酸酸解液中、Ｃｌ－等阴离子，比较其交换容量、柠檬酸的回收率、再生性能、机械强度等。实验表明：Ｄ３１５弱碱性树脂的效果明显优于其它几种树脂。