Enzyme Design from the Bottom Up: An Active Nickel Electrocatalyst with a Structured Peptide Outer Coordination Sphere

Catalytic, peptide‐containing metal complexes with a well‐defined peptide structure have the potential to enhance molecular catalysts through an enzyme‐like outer coordination sphere. Here, we report the synthesis and characterization of an active, peptide‐based metal complex built upon the well‐characterized hydrogen production catalyst [Ni(P^Ph₂N^Ph)₂]²⁺ (P^Ph₂N^Ph=1,3,6‐triphenyl‐1‐aza‐3,6‐diphosphacycloheptane). The incorporated peptide maintains its β‐hairpin structure when appended to the metal core, and the electrocatalytic activity of the peptide‐based metal complex (≈100,000 s^?1) is enhanced compared to the parent complex ([Ni(P^Ph₂N^APPA)₂]²⁺; ≈50,500 s^‐1). The combination of an active molecular catalyst with a structured peptide provides a scaffold that permits the incorporation of features of an enzyme‐like outer‐coordination sphere necessary to create molecular electrocatalysts with enhanced functionality.     

A density functional theory-time-dependent density functional theory investigation of photo-induced hydrogen bond and proton transfer for 2-(3,5-dichloro-2,6-dihydroxy-phenyl)-benzoxazole-6-carboxylicacid

Given the paramount importance of excited-state relaxation in the photochemical process, excited-state hydrogen bonding interactions and excited-state intramolecular proton transfer (ESIPT) are always hot topics. In this work, we theoretically explore the excited-state dynamical behaviors for a novel 2-(3,5-dichloro-2,6-dihydroxy-phenyl)-benzoxazole-6-carboxylicacid (DDPBC) system. As two intramolecular hydrogen bonds (O1 H2⋯N3 and O4 H5⋯O6) exist in the DDPBC structure, we first check if the double proton transfer form cannot be formed in the S1 state. Then, we explore the changes of geometrical parameters involved in hydrogen bonds, based on which we confirm that the dual intramolecular hydrogen bonds are strengthened on photo-excitation. The O1 H2⋯N3 hydrogen bond particularly plays a more important role in excited state. When it comes to the photo-induced excitation, we find charge transfer and electronic density redistribution around O1 H2 and N3 atom moieties. We verify the ESIPT tendency arising from the O1 H2⋯N3 hydrogen bond. In the analysis of the potential energy curves, along with O1 H2⋯N3 and O4 H5⋯O6, we demonstrate that the ESIPT reaction should occur along with O1 H2⋯N3 rather than O4 H5⋯O6. This work not only clarifies the specific ESIPT mechanism for DDPBC system but also paves the way for further novel applications based on DDPBC structure in the future.     

Theoretical investigation of the molecular structure,vibrational spectra,and molecular docking of tramadol using density functional theory

The optimized molecular structures, harmonic vibrational wavenumbers, and the corresponding vibrational assignments of (1S,2S)-tramadol and (1R,2R)-tramadol are computationally examined using the B3LYP density functional theory method together with the standard 6–311++G(d,p) and def2-TVZP basis sets. The optimized structures show that phenolic rings of both 1R,2R and 1S,2S tramadol adopt planar geometry, which are slightly distorted due to the substitution at the meta-position; and the six-membered cyclohexane adopts a slightly distorted chair conformation. The 1S,2S enantiomer is energetically more favorable than 1R,2R with the energy differences of 1.32 and 1.03 kcal/mol obtained at B3LYP/6–311++G(d,p) and B3LYP/Def2-TVZP levels, respectively. The analysis of the binding pocket in the silico molecular docking with the m-opioid receptor shows that it originated two clusters with the 1S,2S enantiomer and one cluster with the 1R,2R enantiomer of tramadol. The results point to a more stable complex of the m-opioid receptor with the 1R,2R enantiomer of tramadol.     

单层类水滑石纳米片的可控合成及规模生产展望

水滑石(LDHs)是一种阴离子黏土材料,由于其主体层板厚度的可调性,使其在光/电催化、电池、超级电容器、传感器以及生物医药等领域都具有广泛应用。降低层厚至单层可使材料的物理化学性质发生根本改变,从而优化催化性能。近期研究表明,利用自上而下,自下而上的方法,可以实现单层LDHs类材料的合成,但是受限于产量(g级)以及成本设备等问题,目前规模化制备高质量单层LDHs类材料还没有工业案例。成核晶化隔离法是目前唯一规模化合成纳米LDHs的工业化方法,具有成本低,产量可吨级放大等优点。本综述从合成方法、表征手段、应用三个角度讨论了单层及超薄LDHs的精准调控,详细论述了近期关于单层及超薄LDHs合成突破以及LDHs的规模化生产进展,并对其性能进行了总结,为后续设计高性能单层LDHs提供思路。     

快速扫描量热法研究聚对苯二甲酸-1,4-环己烷二甲醇酯的结晶和熔融行为

采用快速扫描量热法(FSC)结合传统的差示扫描量热仪(DSC)考察了聚对苯二甲酸-1,4-环己烷二甲醇酯(PCT)聚酯在接近玻璃化转变(T_g)和熔融温度(T_m)范围(100~270 ℃)的结晶和熔融行为。 较大过冷度时PCT聚酯结晶较快,FSC有效地抑制降温过程结晶的发生,而较低过冷度下传统DSC可以避免样品降解对实验结果的影响,二者的结合能很好地对PCT聚酯结晶动力学进行测量,实验结果表明在175 ℃时结晶速率最快。 并且利用Flash DSC对等温结晶温度下形成的片晶熔点进行加热速率的相关测量,在熔融动力学建模的基础上进行校准,以确定零加热速率下片晶的熔点。 Hoffman-Weeks方程中T_m与结晶温度(T_c)的线性关系与T_c=T_m的交点给出了PCT晶体的平衡熔融温度$T_m^o$为315 ℃。     

有序介孔TiO2纳米纤维及其串联光催化水处理-产氢性能（英文）

光催化技术在环境净化及新能源开发方面具有巨大的研究潜力,特别在有机污染物降解去除和分解水制氢展示出了广泛的应用前景.二氧化钛(TiO2)具有出色的光催化活性和稳定性、低成本和无毒性等性质,是最有前景的光催化剂之一,但离广泛实用还有一定距离.TiO2光催化活性很大程度上取决于其尺寸,结晶度和形状等结构特征,因此,TiO2的纳米结构优化设计,为开发高活性TiO2光催化材料,推动其商业和工业应用提供了新的可能.最近大量研究表明,一维(1D)纳米结构,如纳米管,纳米线和纳米纤维等,具有卓越的光生电荷分离和传输能力,可提高光催化活性.鉴于此,1D TiO2纳米光催化剂的设计和可控制备引起了广泛的研究关注.一般而言,1D TiO2制备方法包括溶胶凝胶法,水热法,溶剂热法和静电纺丝法.其中,水热法由于简单高效,是最广泛使用的一种制备方法.通常,水热法制备1D TiO2包括两个主要步骤.首先,在浓NaOH水溶液中的水热处理,将不规则的TiO2颗粒转化为均匀的1D纳米钛酸盐中间体.随后,通过氢离子交换和热转化,将所获得的钛酸盐转化为1D TiO2.钛酸盐中间体的形成和转化过程,对调控所得1D TiO2产物的结构特征,包括相、尺寸、形状和组成等,具有至关重要的作用.然而,传统水热法的反应条件非常苛刻,经常导致1D纳米结构的破坏及纳米颗粒的无序排列,降低了获得材料的光催化活性.因此,发展温和的钛酸盐转化方法,将为制备高活性光催化材料提供新思路.本文通过新颖的蒸汽热方法,成功将钛酸盐纳米带转化为由纳米晶定向组装而成的介孔TiO2纳米纤维.结合XRD,BET,TEM,XPS,UV-Vis和PL等分析手段详细表征了催化剂的组成与结构,基于有机污染物(以罗丹明B为例)降解以及光催化分解水制氢考察了催化剂的光催化活性.结果表明,在150°C蒸汽热处理得到的1D TiO2纳米纤维具有最高的光催化氧化活性与还原活性,均优于商业TiO2(P25).1D TiO2纳米纤维具有介孔结构,其纳米晶排列有序,从而对增强光催化性能至关重要.各向异性锐钛矿纳米晶的有序排列,促进了光生电子与空穴沿纳米纤维结构定向传递,降低电子-空穴复合几率.介孔结构和高表面积有利于光催化反应过程中的质量交换.鉴于1D TiO2纳米纤维同时具有最高的光催化氧化活性与还原活性,我们发展了光催化水处理-产氢集成新技术,通过光催化“有氧氧化-缺氧还原”串联工艺来实现.有机染料在有氧氧化过程中部分氧化,并在后续的缺氧还原阶段充当高效牺牲试剂以促进光催化分解水制氢.该研究为制备高活性有序介孔TiO2纳米纤维及其应用提供了新思路.     

硝酸根接枝诱导组装金红石相TiO2纳米束以增强光催化产氢（英文）

化石燃料的快速消耗加速了全球能源危机和环境污染等问题.光催化产氢直接利用清洁和可持续的太阳能实现向化学燃料的转化,因而成为一种有前景的技术.众多半导体光催化剂中,二氧化钛因其高光催化活性、稳定的化学性质、低成本和无毒等优势而被广泛用作分解水产氢的光催化剂.最近,金红石相TiO2纳米晶体在某些情况下被证明具有光催化的潜力,然而其光生电子-空穴对的快速复合显著抑制了光催化效率.表面修饰、构建异质结和负载助催化剂等策略被用来提高光生载流子的分离效率以减少复合损失,从而提升光催化活性.由于光催化反应通常发生在光催化剂的表面活性位点上,因此通过改善表面性质改变电荷转移途径对光催化活性具有重要影响.磷酸、硫酸、硼酸和盐酸等无机酸的修饰可以改变光催化剂的表面基团,分别通过促进表面羟基的形成和氧气的吸附以及改变表面电荷性质更有效地捕获空穴,实现光生电子和空穴的分离,有助于光催化降解有机污染物.然而,这种影响机制显然不适用于光催化产氢体系,目前对无机酸修饰用于分解水产氢的研究鲜有报道.因此,通过酸改性策略制备高效产氢的光催化剂仍然是一个相当大的挑战.本文利用硝酸诱导策略合成纺锤状金红石相二氧化钛纳米束(R-TiO2).首先,制备层状质子化钛酸盐(LPT)作为TiO2的前体,随后,加入浓硝酸以诱导向金红石相TiO2的转变,并组装形成纺锤状纳米束.对照实验显示,硝酸的酸化可以诱导LPT向金红石相TiO2的转变,而相同条件下浓硝酸后处理不会引起晶相的转变.纺锤形纳米束的形成源于,硝酸诱导R-TiO2沿(110)方向生长并彼此粘附,硝酸诱导组装过程成功在TiO2表面修饰上硝酸根,同时扩大了光吸收范围,有效减少了电荷复合损失.光催化产氢测试证明了R-TiO2光催化剂具有高效的产氢性能,产氢速率为402.4μmol h-1,是Degussa P25的3.1倍,并且显著高于未经浓硝酸处理的锐钛矿(52.0μmol h^-1)或金红石相(110.8μmol h^-1)光催化剂.为了说明表面硝酸根的影响,分别从晶体和化学结构、形态以及表面电荷性质方面比较了光催化反应前后的变化,结果表明,R-TiO2增强的光催化效率可归因于硝酸根基团的负场效应,有利于在表面上捕获带正电的质子以促进载流子分离,提高光催化产氢的效率.总之,本工作不仅对于发展表面修饰策略制备高效产氢光催化剂的研究具有重要意义,而且提出了一种不同于文献报道的无机酸影响机制.     

驱动问题引领下的核心反应在生产实际中的应用复习教学——以“铁和硫酸铜溶液的反应”为例

以铁和硫酸铜溶液的反应在“湿法炼铜”生产实际中的应用复习教学为例,针对学生能力的薄弱点,围绕核心反应搜集丰富的素材,引导学生模拟体会具体反应应用于生产实际时需考虑的问题,以问题解决为线索,达到促进学生发展的目的。     

Highly Selective Production of Ethylene by the Electroreduction of Carbon Monoxide

Conversion of carbon monoxide to high value‐added ethylene with high selectivity by traditional syngas conversion process is challenging because of the limitation of Anderson‐Schulz–Flory distribution. Herein we report a direct electrocatalytic process for highly selective ethylene production from CO reduction with water over Cu catalysts at room temperature and ambient pressure. An unprecedented 52.7 % Faradaic efficiency of ethylene formation is achieved through optimization of cathode structure to facilitate CO diffusion at the surface of the electrode and Cu catalysts to enhance the C?C bond coupling. The highly selective ethylene production is almost without other carbon‐based byproducts (e.g. C₁–C₄ hydrocarbons and CO₂) and avoids the drawbacks of the traditional Fischer–Tropsch process that always delivers undesired products. This study provides a new and promising strategy for highly selective production of ethylene from the abundant industrial CO.     

Engineering the Atomic Interface with Single Platinum Atoms for Enhanced Photocatalytic Hydrogen Production

It is highly desirable but challenging to optimize the structure of photocatalysts at the atomic scale to facilitate the separation of electron–hole pairs for enhanced performance. Now, a highly efficient photocatalyst is formed by assembling single Pt atoms on a defective TiO₂ support (Pt₁/def‐TiO₂). Apart from being proton reduction sites, single Pt atoms promote the neighboring TiO₂ units to generate surface oxygen vacancies and form a Pt‐O‐Ti³⁺ atomic interface. Experimental results and density functional theory calculations demonstrate that the Pt‐O‐Ti³⁺ atomic interface effectively facilitates photogenerated electrons to transfer from Ti³⁺ defective sites to single Pt atoms, thereby enhancing the separation of electron–hole pairs. This unique structure makes Pt₁/def‐TiO₂ exhibit a record‐level photocatalytic hydrogen production performance with an unexpectedly high turnover frequency of 51423 h^?1, exceeding the Pt nanoparticle supported TiO₂ catalyst by a factor of 591.