Dual Atom Catalysts for Energy and Environmental Applications

The pursuit of high metal utilization in heterogeneous catalysis has triggered the burgeoning interest of various atomically dispersed catalysts. Our aim in this review is to assess key recent findings in the synthesis, characterization, structure-property relationship and computational studies of dual-atom catalysts (DACs), which cover the full spectrum of applications in thermocatalysis, electrocatalysis and photocatalysis. In particular, combination of qualitative and quantitative characterization with cooperation with DFT insights, synergies and superiorities of DACs compare to counterparts, high-throughput catalyst exploration and screening with machine-learning algorithms are highlighted. Undoubtably, it would be wise to expect more fascinating developments in the field of DACs as tunable catalysts.     

双原子催化剂:制备、表征和应用

发展可持续和清洁的电化学能源转化技术是应对能源短缺和环境污染挑战的关键一步,燃料电池、电解电池和金属空气电池作为清洁能源储存和转换装置目前得到广泛应用推广,这些装置依靠电催化反应以及电极材料上发生的电荷转移过程来转换电能和化学能.而电催化剂是该类装置电极材料的核心部件,电催化反应的热力学和动力学过程与电催化剂的物理性质和化学状态密切相关.因此探索和开发性能优良、成本低廉的新型电催化剂,将进一步促进这些能源转化技术的商业化应用.单原子催化剂(SACs)以其暴露的活性位点、高选择性和最大限度地原子利用率而受到人们的广泛关注.然而,随着单原子表面自由能的增加,粒子在制备和催化过程中的聚集,催化活性位点的降低和催化剂负荷的相对较低,严重制约了SACs的发展和应用.考虑到SACs的缺点,为了进一步增加单原子活性位点的数量和负载,双原子催化剂(DACs)作为SACs家族成员的扩展近年来逐渐兴起,且两种金属原子(同核/异核)在DACs中的协同作用显著提高了催化剂的催化活性.本文基于当前最新的研究工作对比了同核/异核DACs的不同优势,列举了一系列包括原子层沉积法、湿化学吸附法以及高温热处理法等方法用于制备性能优异的DACs,其中高温热处理法因应用广泛被重点强调.同时,本文也对DACs的表征和识别手段进行了重点概括,包含XANES, EXAFS, IR, DFT等;详细概括和对比了当前DACs在电化学方面的主要应用,如氧还原反应(ORR)和二氧化碳还原反应.目前, DACs作为一个新兴的研究领域,由于其金属原子负载量高、活性位点比SACs更为灵活,已经在电催化领域取得了快速的发展.相对于同核DACs,原则上不同的两个金属原子会组成更多的异核DACs,因此,对于性能优异的异核DACs还有更多的可能性值得深入探索.可以预见, DACs的发展将弥补SACs的不足,在电化学能源的转换和储存方面发挥全面的优势;借助于异核DACs中不同的两个金属原子的多样性,探索以过渡金属为主的DACs,将会为节约贵金属资源及环境保护带来巨大贡献,进一步设计和优化DACs,有利于燃料电池和金属-空气电池创造出更大的经济效益和社会效益.因此,我们相信DACs的发展将成为材料研究的一个新前沿,并为合成更多的高效应用催化剂开辟一条新的途径.     

Single-atom catalysis for organic reactions

Metal-based catalysis, including homogeneous and heterogeneous catalysis, plays a significant role in the modern chemical industry. Heterogeneous catalysis is widely used due to the high efficiency, easy catalyst separation and recycling. However, the metal-utilization efficiency for conventional heterogeneous catalysts needs further improvement compared to homogeneous catalyst. To tackle this, the pursing of heterogenizing homogeneous catalysts has always been attractive but challenging. As a recently emerging class of catalytic material, single-atom catalysts (SACs) are expected to bridge homogeneous and heterogeneous catalytic process in organic reactions and have arguably become the most active new frontier in catalysis field. In this review, a brief introduction and development history of single-atom catalysis and SACs involved organic reactions are documented. In addition, recent advances in SACs and their practical applications in organic reactions such as oxidation, reduction, addition, coupling reaction, and other organic reactions are thoroughly reviewed. To understand structure-property relationships of single-atom catalysis in organic reactions, active sites or coordination structure, metal atom-utilization efficiency (e.g., turnover frequency, TOF calculated based on active metal) and catalytic performance (e.g., conversion and selectivity) of SACs are comprehensively summarized. Furthermore, the application limitations, development trends, future challenges and perspective of SAC for organic reaction are discussed.     

单原子催化剂电子结构调控实现高效多相催化

过去十年见证了单原子催化领域的快速发展,其最高的原子利用效率和充分暴露的活性位点使得单原子催化剂对众多反应的催化活性具有显著提升。在单原子催化领域的早期发展阶段,研究者只是关注单原子催化剂催化活性与催化选择性的提高,而其内在的反应机理以及活性位点同催化性能之间的构效关系往往被忽视。关于单原子催化剂中金属-基底相互作用的深入探讨能够帮助我们理解催化机理,并进一步指导多相催化剂的理性设计。值得注意的是,由于单原子催化剂均一的活性位点及其几何构型,我们可以通过理论计算以及一些原位的表征技术,来揭示其中的金属-基底相互作用,继而进一步促进单原子催化领域的发展以及多相催化剂的理性设计。这篇综述总结了金属-基底相互作用的基本概念,其作用,以及其在一些重要多相催化中的应用,最后提出了金属-基底相互作用在单原子催化领域所面临的挑战与机遇。     

纳米碳材料非金属催化的研究进展

纳米碳材料直接作为催化剂的非金属碳催化是目前材料科学与催化领域的前沿方向之一.相对于传统金属催化剂,纳米碳材料催化剂具有高效环保、低能耗、耐腐蚀等优点.在烃类转化、化学品合成、能源催化等领域表现出优异的催化性能和发展潜力.综述了近年来纳米碳非金属催化研究的最新进展,主要包括新型纳米碳材料的表面性质、催化特性、反应机理和宏观制备等关键问题,并对纳米碳催化存在的挑战和前景进行了展望.     

Multi-functional sites catalysts based on post-synthetic modification of metal-organic frameworks

Multi-functional sites MOFs have been explored as a new type of heterogeneous catalytic materials, which can be constructed by various post-synthetic modifications.     

基于石墨烯基材料的非金属液相催化反应

非金属碳基催化剂因其具有合成简单、结构稳定、比表面积大、可调控性强等特点受到了研究者的关注,已成为最活跃的研究领域之一。以二维、单原子层、六方结构的碳为基础的石墨烯和其高度氧化形态——氧化石墨烯是一类新兴的碳基材料。这类材料在催化领域的应用在近五年内才刚刚兴起。此类材料可用于烃类转化、有机化学合成、能源转化等多种催化反应,本文主要综述了采用化学氧化还原法制备的石墨烯和氧化石墨材料为催化剂的各类催化反应的最新研究进展。     

Regulating the Oxygen Affinity of Single Atom Catalysts by Dual-atom Design for Enhanced Oxygen Reduction Reaction Activity

This work chooses Cu/Fe single-atom catalysts(SACs) with weak/strong oxygen affinity to clarify the effect of dual-atom configuration on oxygen reduction reaction(ORR) performance based on density functional theory(DFT) calculations. The stability and ORR activity of single or dual Cu/Fe atomic sites anchored on nitrogen-doped graphene sheets(Cu-N₄-C, Cu₂-N₆-C, Fe-N₄-C, and Fe₂-N₆-C) are investigated, and the results indicate the dual-atom catalysts(Cu₂-N₆-C and Fe₂-N₆-C) are thermodynamically stable enough to avoid sintering and aggregation. Compared with single-atom active sites of Cu-N₄-C, which show weak oxygen affinity and poor ORR performance with a limiting potential of 0.58 V, the dual-Cu active sites of Cu₂-N₆-C exhibit enhanced ORR activity with a limiting potential up to 0.87 V due to strengthened oxygen affinity. Interestingly, for Fe SACs with strong oxygen affinity, the DFT results show that the dual-Fe sites stabilize the two OH^* ligands structure[Fe₂(OH)₂-N₆-C], which act as the active sites during ORR process, resulting in greatly improved ORR performance with a limiting potential of 0.90 V. This study suggests that the dual-atom design is a potential strategy to improve the ORR performance of SACs, in which the activity of the single atom active sites is limited with weak or strong oxygen affinity.     

碳催化反应:关于氧化脱氢反应的综述(英文)

Carbon mediated catalysis has gained an increasing attention in both areas of nanocatalysis and nanomaterials. The progress in carbon nanomaterials provides many new opportunities to manip-ulate the types and properties of active sites of catalysts through manipulating structures, function-alities and properties of carbon surfaces. The present review focuses on progresses in carbon medi-ated oxidative dehydrogenation reactions of ethylbenzene, propane, and butane. The state-of-the-art of the developments of carbon mediated catalysis is discussed in terms of fundamental studies on adsorption of oxygen and hydrocarbons, reaction mechanism as well as effects of carbon nano-material structures and surface functional groups on the catalytic performance. We highlight the importance and challenges in tuning of the electron density of carbon and oxygen on carbon surfac-es for improving selectivity in oxidative dehydrogenation reactions.     

提高金属有机骨架材料在二氧化碳热催化转化中的性能:策略及前景展望

近年来,大气中CO2的浓度不断增加,带来全球变暖等一系列严重后果,成为国际社会共同关注的环境问题.将CO2催化转化为高附加值化学品可有效降低其向大气中的排放,同时可实现其资源化利用,符合低碳社会的发展目标.目前,已有多种催化体系实现了CO2向不同化学品的转化.然而,由于CO2自身的热力学稳定性和动力学惰性,这些转化通常需要在苛刻的反应条件和较高能耗下进行.设计开发高效催化体系、实现温和条件下CO2的转化利用引起了工业界和学术界的广泛兴趣.金属有机骨架材料(MOFs)是一类由有机配体和金属中心通过配位键组装而成的有机-无机杂化材料,在很多方面展现出良好的应用性能.由于其结构的多样性、可设计性、高比表面积和多孔性等独特性质,MOFs在催化领域吸引了很多研究者的关注.其中,MOFs作为非均相催化剂在CO2热催化转化中表现出良好的应用前景,已实现多种CO2向高值化学品的转化路径.但这些催化体系也存在一些缺点,如有些MOFs材料在催化反应中稳定性差以及其微孔性对反应中的传质造成限制等.因此,设计稳定的MOFs和MOF-基材料并对其结构进行优化改性,从而在温和条件下实现高效的CO2转化具有重要意义.本文综述了提高MOFs在CO2热催化转化反应中性能的几种策略:(1)对MOFs结构中的配体进行设计,包括具有活性官能团的配体、活性配合物作为配体和引入混合配体设计多元MOF;(2)调节MOFs结构中的金属中心,设计混合金属中心和包含活性金属团簇的金属中心;(3)构筑多级孔MOFs;(4)设计MOF-基的复合材料,包括MOFs作为载体与金属纳米颗粒、活性配合物和聚合物构建复合材料;(5)利用MOFs作为前驱体制备MOF-基衍生物材料,重点阐述了如何增加MOFs作为非均相催化剂的催化活性位点以及在CO2转化反应中各位点之间的协同作用.此外,介绍了原位表征技术在MOF-基材料用于CO2固定和转化中的应用.最后,分析了MOF-基非均相催化材料在CO2热催化转化领域目前面临的问题和挑战,包括MOFs材料结构优化、催化机理研究和规模化制备等方面,并对未来的发展趋势进行了展望.     

Boron: A key functional component for designing high-performance heterogeneous catalysts

Heterogeneous catalysis is a vivid branch of traditional catalysis field, with the advantage of high efficiency and being easily separated from reactants and products after reaction, and have received widespread attentions in large-scale industrial production, especially in the field of energy utilization. Boron has been found to be a key functional component for designing high-performance heterogeneous catalysts. In this review, we cover and categorize the past and recent progress in boron-containing materials and their applications in heterogeneous catalysis particularly in energy‐related fields. The fundamental roles of boron components in the emerging heterogeneous catalysis of construction, regulation and stabilization of active phases/sites are highlighted, with the emphasis on how they regulating structural and electronic properties of host materials. We then categorize boron-containing catalysts into six kinds mainly including intermetallic boride catalysts, metal boride-derived catalysts, boron-doped catalysts, metal boride-decorated catalysts, boron-containing compounds as catalyst supports, and single-boron-site catalysts, as well as try to establish structure-catalytic activity relationship. The catalytic applications of these six boron-containing catalysts are discussed separately, focusing on the energy-related reactions such as hydrogen evolution reaction (HER), oxygen evolution reaction (OER), oxygen reduction reaction (ORR), carbon dioxide reduction reaction (CO₂RR) and nitrogen reduction reaction (NRR). Finally, the opportunities and challenges related to boron-containing compounds in the field of catalysis are prospected.     

Homochiral Covalent Organic Frameworks for Asymmetric Catalysis

Owing to their permanent porosity, highly ordered and extended structure, good chemical stability, and tunability, covalent organic frameworks (COFs) have emerged as a new type of organic materials that can offer various applications in different fields. Benefiting from the huge database of organic reactions, the required functionality of COFs can be readily achieved by modification of the corresponding organic functional groups on either polymerizable monomers or established COF frameworks. This striking feature allows homochiral covalent organic frameworks (HCCOFs) to be reasonably designed and synthesized, as well as their use as a unique platform to fabricate asymmetric catalysts. This contribution provides an overview of new progress in HCCOF-based asymmetric catalysis, including design, synthesis, and their application in asymmetric organic synthesis. Moreover, major challenges and developing trends in this field are also discussed. It is anticipated that this review article will provide some new insights into HCCOFs for heterogeneous asymmetric catalysis and help to encourage further contributions in this young but promising field.     

The nature of the active site in heterogeneous metal catalysis

This tutorial review, of relevance for the surface science and heterogeneous catalysis communities, provides a molecular-level discussion of the nature of the active sites in metal catalysis. Fundamental concepts such as "Br?nsted-Evans-Polanyi relations" and "volcano curves" are introduced, and are used to establish a strict partitioning between the so-called "electronic" and "geometrical" effects. This partitioning is subsequently employed as the basis for defining the concept "degree of structure sensitivity" which can be used when analyzing the structure sensitivity of catalytic reactions.     

Catalytic palladium nanoparticles supported on nanoscale MOFs: a highly active catalyst for Suzuki–Miyaura cross-coupling reaction

Pd nanoparticles have been successfully supported on nanoscale metal-organic frameworks (NMOFs) by using a simple and effective microwave-assisted impregnation process. The resulting composite, representing as a highly active NMOFs supported metal nanoparticles catalyst for the Suzuki cross-coupling reaction between aryl/heteroaryl halides and arylboronic acids, is well characterized, and its high activity and good recyclability are discussed in details. It reveals that, compared to the corresponding bulk MOFs and conventional active carbon materials, nanoscale MOFs as novel support materials for heterogeneous catalysts can exhibit superior performance in the catalytic reactions.     

Regulation of Electrocatalytic Activity by Local Microstructure: Focusing on the Catalytic Active Zone

Traditional regulation methods of active sites have successfully optimized the performance of electrocatalysts, but seem unable to achieve further breakthrough in the catalytic activity. Unlike the conventional viewpoint of focusing on single active site, the concept of local microstructure active zone is more comprehensive and new methods to regulate the reaction zone for electrocatalytic reactions are developed accordingly. The local microstructure active zone refers to the zone with high catalytic activity formed by the interaction between active atoms and neighboring coordination atoms as well as the surrounding environment. Instead of the traditional single active atom site, the active zone is more suitable for the actual electrochemical reaction process. According to this concept, the activity of electrocatalysts can be coordinated by multiple active atoms. This strategy is beneficial for understanding the relationship between material, structure, and catalysis, which realizes the design and synthesis of high-performance electrocatalysts. This review provides the research progress of this strategy for electrocatalytic reactions, with emphasis on their applications in oxygen evolution reaction, urea oxidation reaction, and carbon dioxide reduction.     

Recent Advances in Multifunctional Capsule Catalysts in Heterogeneous Catalysis?

Capsule catalysts composed of pre-shaped core catalysts and layer zeolites have been widely used in the tandem reactions where multiple continuous reactions are combined into one process. They show excellent catalytic performance in heterogeneous catalysis, including the direct synthesis of middle isoparaffins or dimethyl ether from syngas, as compared to the conventional hybrid catalysts. The present review highlights the recent development in the design of capsule catalysts and their catalytic applications in heterogeneous catalysis. The capsule catalyst preparation methods are introduced in detail, such as hydrothermal synthesis method, dual-layer method, physically adhesive method and single crystal crystallization method. Furthermore, several new applications of capsule catalysts in heterogeneous catalytic processes are presented such as in the direct synthesis of liquefied petroleum gas from syngas, the direct synthesis of para-xylene from syngas and methane dehydroaromatization. In addition, the development in the design of multifunctional capsule catalysts is discussed, which makes the capsule catalyst not just a simple combination of two different catalysts, but has some special functions such as changing the surface hydrophobic or acid properties of the core catalysts. Finally, the future perspectives of the design and applications of capsule catalysts in heterogeneous catalysis are provided.     

多相催化剂活性位点的配位环境及其对催化性能的影响

多相催化技术在化工产业中一直发挥着重要作用,近年来也被广泛应用于燃料电池、绿色化学、纳米技术、生物技术等新兴领域.其中,金属催化剂在加氢、氧化、氢甲酰化、偶联等多种反应中表现出较高的催化效率.然而社会发展对金属催化剂的效率提出了更高的要求,针对特定反应,开发兼具高活性、高选择性和优良稳定性的理想催化剂一直是学术界和工业...     

Recent advances in annulations enabled by nucleophilic Lewis base/metal dual catalysis

Metal/nucleophilic Lewis base dual catalysis has been recognized as a reliable and promising strategy for finishing ideal organic synthesis over the past decades. The new strategy can usually achieve some chemical reactions that cannot be realized by the traditionally mono-catalytic system, dramatically expanding the synthetic utility of chemical transformations by leveraging additional activation modes. Thus considerable progress has been made in the synthesis of a wide range of heterocyclic and biologically active compounds by using the combination of diversely metal/nucleophilic Lewis base dual catalysts, including metal/phosphine, metal/N-heterocyclic carbene (NHC) and metal/tertiary amine dual catalysis systems. In this review, we describe a comprehensive and updated advance of metal/nucleophilic Lewis base dual catalytic annualtion reactions, meanwhile, the related mechanism and the application of these annulation strategies in natural product total synthesis will be highlighted in detail.     

Nanostructured Heterogeneous Catalysts for Bioorthogonal Reactions

Bioorthogonal chemistry has inspired a new subarea of chemistry providing a powerful tool to perform novel biocompatible chemospecific reactions in living systems. Following the premise that they do not interfere with biological functions, bioorthogonal reactions are increasingly applied in biomedical research, particularly with respect to genetic encoding systems, fluorogenic reactions for bioimaging, and cancer therapy. This Minireview compiles recent advances in the use of heterogeneous catalysts for bioorthogonal reactions. The synthetic strategies of Pd-, Au-, and Cu-based materials, their applicability in the activation of caged fluorophores and prodrugs, and the possibilities of using external stimuli to release therapeutic substances at a specific location in a diseased tissue are discussed. Finally, we highlight frontiers in the field, identifying challenges, and propose directions for future development in this emerging field.     

催化剂活性位本质和构效关系的模型催化研究

明确催化剂的活性位本质和构建多相催化的结构和反应性能之间的准确关系是催化基础研究的重点,表面科学研究基于丰富的表征测试手段能够较好地在分子原子水平测定表面结构以明确催化剂活性位本质,并通过高压原位反应池测定相关催化反应性能,获得较可靠的催化剂构效关系。本文简要总结了近年来本人参与的几个模型催化研究例子,包括贵金属表面上CO和烷烃催化氧化的活性表面、纳米Au膜的制备和CO氧化的催化活性位、VO_x/Pt(111)上丙烷氧化的协同作用、Au Pd合金上醋酸乙烯酯合成Au的助催化作用、模型氧化物上纳米Pt的庚烷脱氢环化制甲苯的粒径关系等,以及相关模型催化研究技术的进展。