热稳定单原子催化剂的理性构筑:从原子级结构到实际应用

80%以上的工业生产过程涉及催化,如化工生产、能源转换、制药和废物处理等等.催化剂的使用显著提高了生产效率,降低了生产成本,为国民经济、地球环境和人类文明的可持续发展做出了很大贡献.为了满足日益增长的生产需求和最大的经济效益,开发高效、稳定、低成本的新型催化剂已成为当务之急.金属中心负载在载体上的负载型金属催化剂因其较好的催化活性和相对较低的金属用量而受到广泛关注.研究发现,负载型结构可增强传热和传质并增加活性金属中心的分散度,从而影响催化性能.此外,负载金属的颗粒尺寸对催化剂的性能有很大影响.迄今为止,科学家们一直在通过减小金属颗粒尺寸和提高原子利用效率来提高催化剂的活性.原子级尺寸的颗粒通常表现出与大尺寸颗粒显着不同的物理和化学性质,而当活性位点的尺寸缩小到单个原子时,单原子催化剂的概念应运而生.对于单原子催化剂,金属原子中心通过配位被载体中的缺陷锚定,从而调整金属原子的电子云分布.这种配位调整使得单原子催化剂拥有与传统催化剂不同的性能.作为催化领域的新前沿,单原子催化剂已经在许多催化反应中表现出前所未有的活性和选择性.然而,许多报道的单原子催化剂在高温环境或长期催化应用中容易受到奥斯特瓦尔德熟化过程的影响,从而导致催化剂烧结和失活.而烧结的原因在于金属原子和载体之间较弱的相互作用.失活催化剂的再生和回收将大大增加工业生产的时间和经济成本.因此,开发具有优异热稳定性的单原子催化剂以满足工业需求是十分必要的.本综述首先总结了近年来关于热稳定型单原子催化剂合成方法的基础研究,并从原子尺度上分析了这些方法所构建的金属中心的结构形态和配位环境.此外,结合近些年的研究中新的表征技术与理论计算手段解释了热稳定性的来源.重点讨论了热稳定单原子催化剂的实际催化应用.分析了热稳定单原子催化剂在热催化应用中的独特作用机理、并尝试为确定催化过程中真正的活性中心以及通过原子级调控手段进行高活性热稳定单原子催化剂的合成提供理论指导.最后总结了热稳定单原子催化剂发展的主要问题,并简要分析了单原子催化领域的研究挑战和发展前景.     

单分子层受限冰-水共存界线毛细波与固-液相变动力学

冰-水界面动力学性质在冰形核、生长、表界面熔化中扮演核心角色,长期以来一直被广泛关注.然而,受限水体系中冰-水界面的动力学性质却鲜有报道.本工作利用平衡态分子动力学模拟方法和受限固-液两相平衡模拟技术,对两种水模型(恒定偶极矩、可极化)描述的单分子层受限冰-水两相平衡体系中的一维固-液界线开展研究.通过对一维受限冰-水...     

Insertion Chemistry of Lutetacyclopropene toward Unsaturated C−O/C−N Bonds

Although the reaction chemistry of transition metallacyclopropenes has been well-established in the last decades, the reactivity of rare-earth metallacyclopropenes remains elusive. Herein, we report the reaction of lutetacyclopropene 1 toward a series of unsaturated molecules. The reaction of 1 with one equiv. of PhCOMe, Ar¹CHO (Ar¹=2,6-Me₂C₆H₃), W(CO)₆, and PhCH=NPh provided oxalutetacyclopentenes, metallacyclic lutetoxycarbene, and azalutetacyclopentene via 1,2-insertion of C=O, C≡O, or C=N bonds into Lu−C_sp2 bond, respectively. However, the reaction between 1 and Ar²N=C=NAr² (Ar²=4-MeC₆H₄) gave an acyclic lutetium complex with a diamidinate ligand by the coupling of one molecule of 1 with two carbodiimides, irrespective of the amount of carbodiimide employed. More interestingly, when 1 was treated with two equiv. of Ar¹CHO, the reductive coupling of two C=O bonds was discovered to give a lutetium pinacolate complex along with the release of tolan. Remarkably, the reactivity of 1 is significantly different from that of scandacyclopropenes; these metallacycles derived from 1 all represent the first cases in rare-earth organometallic chemistry.     

硫化铟锌的改性合成及光催化特性

随着社会经济的高速发展,能源的短缺和生态的破坏引起了人们的关注。近年来,寻找合适的解决方案已成为关注的重点。作为一种绿色环保技术,光催化由于其高效、低成本等优点而成为能源和环境问题的研究热点。在许多光催化材料中,三元硫化物硫化铟锌(ZnIn₂S₄)由于具有可见光响应特性、简单的制备方法和出色的稳定性而表现出巨大的潜力。然而,较高的载流子复合率限制了其光催化性能。近年来,许多研究报道了改性ZnIn₂S₄以提高其光催化性能,在此,本文详细介绍了各种改性研究,包括ZnIn₂S₄单体的合成、半导体化合物的结构、贵金属沉积、碳元素改性、离子掺杂。然后,系统完整地总结了ZnIn₂S₄在光催化、降解有机污染物、去除六价铬、还原CO₂和有机合成等方面表现出的光催化特性和机理。最后,对ZnIn₂S₄的发展前景提出了展望,以期ZnIn₂S₄光催化剂得到更广泛和深入的研究,尽快在实际生产中得到应用。     

还原-氧化协同降解全/多卤代有机污染物

全/多卤代有机污染物大多具有生态毒性、生物蓄积性、环境持久性及长距离迁移性,不仅危害环境与生态安全,而且可经食物链传递威胁人类健康。由于卤原子是吸电子基团且取代数目多,这类物质的最高占据分子轨道能较低,难于被氧化降解,相反较易被还原法脱卤降解。随卤原子取代数减少,脱卤产物难被进一步还原,而其毒性甚至高于母体污染物。注意到低卤代有机物更容易发生氧化降解,一些研究构建了还原-氧化接力降解体系,即先利用还原法将全/多卤代有机污染物还原为低卤代产物,再利用氧化法降解这些中间产物,从而实现深度/完全脱卤和矿化。本文根据催化反应类型对还原-氧化联用法进行了归纳,分类介绍了基于传统化学催化、光催化、电化学、光电化学及机械化学等构建还原-氧化协同降解体系的原理及应用,以期为开发高效的处置技术提供思路和建议。     

Enhanced Four-Electron Oxygen Reduction Selectivity of Clamp-Shaped Cobalt(II) Porphyrin(2.1.2.1) Complexes

The molecular structure, electrochemistry, spectroelectrochemistry and electrocatalytic oxygen reduction reaction (ORR) features of two Co^II porphyrin(2.1.2.1) complexes bearing Ph or F₅Ph groups at the two meso-positions of the macrocycle are examined. Single crystal X-ray analysis reveal a highly bent, nonplanar macrocyclic conformation of the complex resulting in clamp-shaped molecular structures. Cyclic voltammetry paired with UV/Vis spectroelectrochemistry in PhCN/0.1 M TBAP suggest that the first electron addition corresponds to a macrocyclic-centered reduction while spectral changes observed during the first oxidation are consistent with a metal-centered Co^II/Co^III process. The activity of the clamp-shaped complexes towards heterogeneous ORR in 0.1 M KOH show selectivity towards the 4e⁻ ORR pathway giving H₂O. DFT first-principle calculations on the porphyrin catalyst indicates a lower overpotential for 4e⁻ ORR as compared to the 2e⁻ pathway, consistent with experimental data.     

Photocatalytic Free Radical-Controlled Synthesis of High-Performance Single-Atom Catalysts

Single-atom catalysts (SACs) have emerged as crucial players in catalysis research, prompting extensive investigation and application. The precise control of metal atom nucleation and growth has garnered significant attention. In this study, we present a straightforward approach for preparing SACs utilizing a photocatalytic radical control strategy. Notably, we demonstrate for the first time that radicals generated during the photochemical process effectively hinder the aggregation of individual atoms. By leveraging the cooperative anchoring of nitrogen atoms and crystal lattice oxygen on the support, we successfully stabilize the single atom. Our Pd₁/TiO₂ catalysts exhibit remarkable catalytic activity and stability in the Suzuki–Miyaura cross-coupling reaction, which was 43 times higher than Pd/C. Furthermore, we successfully depose Pd atoms onto various substrates, including TiO₂, CeO₂, and WO₃. The photocatalytic radical control strategy can be extended to other single-atom catalysts, such as Ir, Pt, Rh, and Ru, underscoring its broad applicability.     

Luminescent zinc salen complexes as single and two-photon fluorescence subcellular imaging probes

A novel class of ZnSalens (ZnL(1-10)) with lipophilic and cationic conjugates as optical probes in single and two-photon fluorescence microscopy images of living cells were prepared, which exhibited chemo- and photostability, low cytotoxicity and high subcellular selectivity.     

RgBF2(+) complexes (Rg = Ar, Kr, and Xe): the cations with large stabilities

Rare gas containing cations with general formula [Rg, B, 2F](+) have been investigated theoretically by second-order Mo?ller-Plesset perturbation, coupled cluster, and complete active space self-consistent field levels of theory with correlation-consistent basis sets. Totally two types of minima, i.e., boron centered C(2) (v) symmetried RgBF(2) (+) (Rg = Ar, Kr, and Xe) which can be viewed as loss of F(-) from FRgBF(2) and linear FRgBF(+) (Rg = Kr and Xe) are obtained at the CCSD(T)∕aug-cc-pVTZ∕SDD and CASSCF(10,8)∕aug-cc-pVTZ∕SDD levels, respectively. It is shown that the RgBF(2) (+) are global minima followed by FRgBF(+) at 170.9 and 142.2 kcal∕mol on the singlet potential-energy surfaces of [Rg, B, 2F](+) (Rg = Kr and Xe) at the CASPT2(10,8) ∕aug-cc-pVTZ∕SDD∕∕CASSCF(10,8)∕aug-cc-pVTZ∕SDD, respectively. The interconversion barrier heights between RgBF(2) (+) and FRgBF(+) (Rg = Kr and Xe) are at least 39 kcal∕mol. In addition, no dissociation transition state associated with RgBF(2) (+) and FRgBF(+) can be found. This suggests that RgBF(2) (+) (Rg = Ar, Kr, and Xe) can exist as both thermodynamically and kinetically stable species, while linear FRgBF(+) (Rg = Kr and Xe) can exist as metastable species compared with the lowest dissociation limit energies just like isoelectronic linear FRgBO and FRgBN(-). From natural bond orbital and atoms-in-molecules calculations, it is found that the positive charge is mainly located on Rg and boron atoms for both types of minima, the Rg-B bonds of ArBF(2) (+), KrBF(2) (+), and XeBF(2) (+) are mostly electrostatic, thus can be viewed as ion-induced dipole interaction; while that of linear FKrBF(+) and FXeBF(+) are covalent in nature. The previous experimental observation of ArBF(2) (+) by Pepi et al. [J. Phys. Chem. B. 110, 4492 (2006)] should correspond to C(2) (v) minimum. The presently predicted spectroscopies of KrBF(2) (+), XeBF(2) (+), FKrBF(+), and FXeBF(+) should be helpful for their experimental identification in the future.     

A [001]-Oriented Hittorf's Phosphorus Nanorods/Polymeric Carbon Nitride Heterostructure for Boosting Wide-Spectrum-Responsive Photocatalytic Hydrogen Evolution from Pure Water

Red phosphorus is a promising photocatalyst with wide visible-light absorption up to 700 nm, but the fast charge recombination limits its photocatalytic hydrogen evolution reaction (HER) activity. Now, [001]-oriented Hittorf's phosphorus (HP) nanorods were successfully grown on polymeric carbon nitride (PCN) by a chemical vapor deposition strategy. Compared with the bare PCN and HP, the optimized PCN@HP hybrid exhibited a significantly enhanced photocatalytic activity, with HER rates reaching 33.2 and 17.5 μmol h⁻¹ from pure water under simulated solar light and visible light irradiation, respectively. It was theoretically and experimentally indicated that the strong electronic coupling between PCN and [001]-oriented HP nanorods gave rise to the enhanced visible light absorption and the greatly accelerated photoinduced electron–hole separation and transfer, which benefited the photocatalytic HER performance.