The fabrication strategies and enhanced performances of metal-organic frameworks and carbon dots composites: State of the art review

Metal-organic frameworks (MOFs) with large specific surface area, considerable pore volume, controllable structure, and high concentration of active metal sites have been applied widely in researches like catalysis and sensing. However, potential applications of MOFs in both photocatalysis and luminescence sensors are facing major challenges arising from their severe charge recombination, low utilization of solar energy, low quantum yield, limited charge transfer between the metal ions/clusters and the ligand. Recent studies revealed that rational introduction of carbon dots (CDs) with excellent optical properties, unique quantum confinement and high conductivity can greatly enhance the functions of MOFs. In this paper, typical synthesis methods of these CD-MOF composites as well as their potential applications in photocatalysis and sensing are reviewed with emphasis. Representative examples of these CD-MOF composites are discussed, and key features and advantages of CD-MOF composites that will facilitate future applications are highlighted.     

金属有机骨架及其复合材料在分离领域中的应用进展

金属有机骨架（MOFs）是一类由无机金属离子与有机配体自组装形成的新型有机-无机杂化多孔材料,因具有比表面积超高、结构多样、热稳定性良好、孔道尺寸和性质可调等优势,在分离领域表现出重要的应用价值。然而,采用传统方法制备的MOFs多为粒径在微米或亚微米尺度的晶体,且颗粒形貌不规则,因此限制了MOFs在样品前处理和色谱固定相等领域的应用和发展。构建基于MOFs的复合材料是弥补MOFs应用缺陷的一项有效措施,有望在保留MOFs优越的分离特性的同时,引入基体材料的特定性能。该文简要综述了近年来MOFs及其复合材料在吸附、样品前处理和色谱固定相等分离领域中的应用进展,并对MOFs在分离科学中的应用前景做出展望。     

Surface-Enhanced Raman Spectroscopy: Principles,Methods, and Applications in Energy Systems†

Surface-enhanced Raman spectroscopy (SERS) has advanced significantly since its inception. Numerous experimental and theoretical efforts have been made to understand the SERS effect and demonstrate its potential. Due to its extremely high sensitivity and selectivity and ability to provide molecular fingerprint information, SERS has a wide range of applications in surface and interfacial chemistry, energy, materials, biomedicine, environmental analysis, etc. This review aims to provide readers with an understanding of the principles, methodologies, and applications of SERS. We briefly introduce the fundamental theory of the SERS enhancement mechanism and summarize the details of the preparation of SERS-active substrates. Recent applications of SERS in energy systems are then highlighted, including probing surface reactions and interfacial charge transfer of batteries and electrocatalysts. Finally, the challenges and prospects of SERS research are discussed.     

Metal-Organic Framework Composites and Their Derivatives as Efficient Electrodes for Energy Storage Applications: Recent Progress and Future Perspectives

Metal-organic frameworks (MOFs) have been important electrochemical energy storage (EES) materials because of their rich species, large specific surface area, high porosity and rich active sites. Nevertheless, the poor conductivity, low mechanical and electrochemical stability of pristine MOFs have hindered their further applications. Although single component MOF derivatives have higher conductivity, self-aggregation often occurs during preparation. Composite design can overcome the shortcomings of MOFs and derivatives and create synergistic effects, resulting in improved electrochemical properties for EES. In this review, recent applications of MOF composites and derivatives as electrodes in different types of batteries and supercapacitors are critically discussed. The advantages, challenges, and future perspectives of MOF composites and derivatives have been given. This review may guide the development of high-performance MOF composites and derivatives in the field of EES.     

Recent Advances on Confining Noble Metal Nanoparticles Inside Metal-Organic Frameworks for Hydrogenation Reactions

Hydrogenation reaction is one of the pillars of the chemical industry for the synthesis of drugs and fine chemicals. To achieve high catalytic performance, it is still highly desirable for constructing novel supported metal catalysts. Different from conventional supports like metal oxides, zeolites and carbon materials, metal-organic frameworks(MOFs) as the emerging porous materials have Hexhibited great potential to host metal nanoparticles (NPs) for achieving hydrogenation reactions with high catalytic efficiency, due to their unique porous structures. Recently, many progresses have been made, and thus, it is necessary to summarize the recent progresses on confining metal NPs inside MOFs for hydrogenation reactions. In this review, we first introduced the general synthesis methods for confining noble metal NPs inside MOFs. Then, the applications of noble metal NPs/MOFs catalysts in hydrogenation reactions were summarized, and the synergistic catalytic performances among noble metal NPs, metal nodes, functional groups, and pore channels in MOFs were illustrated. Subsequently, the hydrogen spillover effect involved in the hydrogenation reactions was discussed. Finally, we provide an outlook on the future research directions and challenges of confining noble metal NPs inside MOFs for hydrogenation reactions.     

Noble‐Metal‐Free Materials for Surface‐Enhanced Raman Spectroscopy Detection

Surface‐enhanced Raman spectroscopy (SERS) is an attractive tool for the sensing of molecules in the fields of chemical and biochemical analysis as it enables the sensitive detection of molecular fingerprint information even at the single‐molecule level. In addition to traditional coinage metals in SERS analysis, recent research on noble‐metal‐free materials has also yielded highly sensitive SERS activity. This Minireview presents the recent development of noble‐metal‐free materials as SERS substrates and their potential applications, especially semiconductors and emerging graphene‐based nanostructures. Rather than providing an exhaustive review of this field, possible contributions from semiconductor substrates, characteristics of graphene enhanced Raman scattering, as well as effect factors such as surface plasmon resonance, structure and defects of the nanostructures that are considered essential for SERS activity are emphasized. The intention is to illustrate, through these examples, that the promise of noble‐metal‐free materials for enhancing detection sensitivity can further fuel the development of SERS‐related applications.     

Thermocatalytic Conversion of CO2 to Valuable Products Activated by Noble-Metal-Free Metal-Organic Frameworks

Thermocatalysis of CO₂ into high valuable products is an efficient and green method for mitigating global warming and other environmental problems, of which Noble-metal-free metal–organic frameworks (MOFs) are one of the most promising heterogeneous catalysts for CO₂ thermocatalysis, and many excellent researches have been published. Hence, this review focuses on the valuable products obtained from various CO₂ conversion reactions catalyzed by noble-metal-free MOFs, such as cyclic carbonates, oxazolidinones, carboxylic acids, N-phenylformamide, methanol, ethanol, and methane. We classified these published references according to the types of products, and analyzed the methods for improving the catalytic efficiency of MOFs in CO₂ reaction. The advantages of using noble-metal-free MOF catalysts for CO₂ conversion were also discussed along the text. This review concludes with future perspectives on the challenges to be addressed and potential research directions. We believe that this review will be helpful to readers and attract more scientists to join the topic of CO₂ conversion.     

金属-有机框架衍生的多功能光催化剂

在光催化过程中,光催化剂被太阳能激发产生光生电子和空穴,来实现环境净化或能量转换,是应对全球变暖和能源短缺的有效途径之一.然而,光催化技术面临的主要瓶颈问题是光生载流子的低分离效率和高反应能垒.而催化剂本身的特性对这一点起到了决定性的作用.因此,催化剂的合理设计和改性是提高光催化效率的关键.金属有机框架(MOFs)是一类由金属节点和有机配体组成的新型结晶多孔材料.基于结构多样性、超高比表面积、形状和尺寸可调的纳米孔或纳米通道等优异的特性,MOFs基材料在光催化领域引起了广泛关注.然而,MOFs的主要问题之一是低导电性和稳定性,这限制了其更广泛应用.正是由于MOFs的不稳定性,其可以作为牺牲模板制备纳米材料.由MOFs衍生的纳米材料继承了MOFs的优异特性,同时避免了MOFs较差的导电性和稳定性的问题.并且可以通过选择特定的金属节点和有机配体对MOFs衍生的纳米材料进行调控,从而实现光催化剂的多功能性.因此,MOFs衍生物在光催化领域展现出更广阔的应用前景.而且MOFs衍生物不仅可以作为半导体光催化剂,还可以作为光催化析氢、CO₂还原、污染物降解等反应的助催化剂.本文重点介绍MOFs衍生物在光催化领域的多功能应用.从MOFs衍生物的制备、修饰和应用等方面对近年来的研究进行了分析和总结.最后,对MOFs衍生物应用于光催化领域的挑战进行了分析,并对未来发展和机遇进行了展望,以期为该领域的进一步研究提供更多参考,并带来新的启示.     

Recent advances in metal‐organic frameworks and covalent organic frameworks for sample preparation and chromatographic analysis

In the field of analytical chemistry, sample preparation and chromatographic separation are two core procedures. The means by which to improve the sensitivity, selectivity and detection limit of a method have become a topic of great interest. Recently, porous organic frameworks, such as metal‐organic frameworks (MOFs) and covalent organic frameworks (COFs), have been widely used in this research area because of their special features, and different methods have been developed. This review summarizes the applications of MOFs and COFs in sample preparation and chromatographic stationary phases. The MOF‐ or COF‐based solid‐phase extraction (SPE), solid‐phase microextraction (SPME), gas chromatography (GC), high‐performance liquid chromatography (HPLC) and capillary electrochromatography (CEC) methods are described. The excellent properties of MOFs and COFs have resulted in intense interest in exploring their performance and mechanisms for sample preparation and chromatographic separation.     

Minireview: Recent Advances in Surface-Enhanced Raman Scattering-Based Nucleic Acid Detection with Application to Pathogen Diagnosis

Surface-enhanced Raman scattering (SERS) is a promising analytical tool in nanoscale detection because of its high sensitivity and selectivity. This review focuses on recent advances in SERS-based detection of DNA and RNA. First, nanostructure-based SERS-active substrates are introduced. Using label-free and labeled SERS, target biomolecules such DNA, RNA and microRNA have been successfully detected. Finally, applications in pathogen diagnosis are discussed. The prospects and challenges of SERS-based bioanalysis are highlighted.     

Yolk-Shell Nanostars@Metal Organic Frameworks as Molecular Sieves for Optical Sensing and Catalysis

Hybrid composites between nanoparticles and metal organic frameworks (MOFs) have been described as optimal materials for a wide range of applications in optical sensing, drug delivery, pollutant removal or catalysis. These materials are usually core-shell single- or multi-nanoparticles, restricting the inorganic surface available for reaction. Here, we develop a method for the preparation of yolk-shells consisting in a plasmonic gold nanostar coated with MOF. This configuration shows more colloidal stability, can sieve different molecules based on their size or charge, seems to show some interesting synergy with gold for their application in photocatalysis and present strong optical activity to be used as SERS sensors.     

MOFs for desulfurization of fuel oil: Recent advances and future insights

Nowadays, desulfurization of fuel oil has raised concern globally because of strict industrial and environmental legislations. Albeit hydrodesulfurization (HDS) has been extensively used in oil refineries to produce low sulfur oil (< 10 ppm) but not been proven as effective method for the removal of dibenzothiophene (DBT), benzothiophene (TH) and their derivatives. Subsequently, adsorptive desulfurization (ADS) and oxidative desulfurization (ODS) methods have been developed to achieve high removal efficiency. In the past decade, metal–organic frameworks (MOFs) and its composites as oxidative catalysts, as well as adsorbents, have attracted the researchers owing to high surface area, tunable properties, and reusable. The present review comprises use of MOFs and their composites for the removal of sulfur from fuel oil via ODS and ADS processes. Additionally, physicochemical properties of MOFs, mechanism, pros and cons of both process, regeneration, and future challenges have been discussed briefly. Moreover, current limitations and future prospective are also discussed.     

Sorptive extraction of pesticides from food and environmental samples using metal organic framework-based adsorbents

Sorptive pre-concentration of pesticide residues in food and environmental samples is increasingly gaining momentum. This can be attributed to fact that most sorptive extraction techniques are solvent-free as well as the availability of emerging sorbents with relatively high adsorption capacities. Metal organic frameworks (MOFs) are among the emerging sorbents that have captured the interests of many researchers during pesticide analysis. There are many types of MOFs that have been used by researchers to pre-concentrate pesticides in food and environmental samples. Some researchers have successfully used MIL-based MOFs during sorptive extraction of pesticides in complex matrices. This review gives a detailed discussion of their application during pesticide pre-concentration. Other researchers have used the ZIF series of MOFs for the sorptive pre-concentration of pesticides in food and environmental samples. The utilisation of the ZIF series of MOFs during pesticide pre-concentration is well-articulated in this review. The review also devoted to the application of UiO and HKUST series of MOFs during the pre-concentration of pesticides in food and environmental samples. In addition, the challenges associated with the use of MOFs during sorptive pre-concentration of pesticides are also discussed in this review.     

Progresses on electrospun metal–organic frameworks nanofibers and their wastewater treatment applications

Metal–organic frameworks (MOFs) have been proven to be outstanding adsorbent materials which possess excellent pollutant removal performances in wastewater treatment. However, MOFs consumption, loss, or blockage in reactor pipelines as well as the long and complicated recycling process severely limit their practical applications. Therefore, construction of novel MOFs composites with extremely high ease-of-use property has become a research hotspot, such as two-dimensional (2D) MOFs fibrous membranes. In this review, the exploitation of MOFs nanofibrous membranes via electrospinning and their applications in wastewater treatment are summarized. The MOFs nanofibers (NFs) architectures are established systematically by five routes: (1) direct electrospinning of MOFs-polymer; (2) induced growth of MOFs on electrospun NFs containing seeds; (3) growth of MOFs on electrospun organic NFs’ (4) growth of MOFs on electrospun inorganic NFs; and (5) simultaneous electrospinning and electrospraying. Furthermore, the applications of different types of MOFs nanofibrous membranes and their derivatives in water treatment and purification are discussed, including oil-water separation, the removal of heavy metal ions, organic dyes, personal care products, non-steroidal anti-inflammatory drugs (NSAIDs) and so on. The adsorption properties and mechanisms of electrospun MOFs nanofibrous membranes towards various environmental pollutants are discussed. Finally, the challenges of electrospun MOFs NFs, the limitations of their applications, and future development trends are prospected.     

Electrochemical surface-enhanced Raman spectroscopy of nanostructures

This tutorial review first describes the early history of SERS as the first SERS spectra were obtained from an electrochemical cell, which led to the discovery of the SERS effect in mid-1970s. Up to date, over 500 papers have been published on various aspects of SERS from electrochemical systems. We then highlight important features of electrochemical SERS (EC-SERS). There are two distinctively different properties of electric fields, the electromagnetic field and static electrochemical field, co-existing in electrochemical systems with various nanostructures. Both chemical and physical enhancements can be influenced to some extent by applying an electrode potential, which makes EC-SERS one of the most complicated systems in SERS. Great efforts have been made to comprehensively understand SERS and analyze EC-SERS spectra on the basis of the chemical and physical enhancement mechanisms in order to provide meaningful information for revealing the mechanisms of electrochemical adsorption and reaction. The EC-SERS experiments and applications are then discussed from preparation of nanostructured electrodes to investigation of SERS mechanisms and from characterization of adsorption configuration to elucidation of electrochemical reaction mechanisms. Finally, prospective developments of EC-SERS in substrates, methods and theory are discussed.     

Metal−Organic Frameworks toward Electrochemical Sensors: Challenges and Opportunities

Owing to their fascinating characteristics, metal?organic frameworks (MOFs) have attracted great attention and been utilized in a range of applications. The use of MOFs in electrochemical sensors has become an emerging subfield since 2013. However, the poor chemical stability in aqueous solutions and low electrical conductivity of most MOFs become two main concerns that hinder the use of pristine MOFs in electroanalytical systems. In this short review, we aim to focus on these issues and provide perspectives regarding the opportunities and possible strategies in future studies to overcome these challenges in order to design the MOF‐based electrochemical sensors.     

表面增强拉曼光谱在毒品检测中的应用进展

表面增强拉曼光谱(surfaced-enhanced Raman spectroscopy,SERS)作为一种借助贵金属纳米材料可以增强目标分子信号的拉曼光谱技术,由于其具有指纹识别、高灵敏、高准确度、快速无损、不受水分子干扰等特点,在法庭科学领域中的痕量毒品检测方面逐渐受到人们的关注.SERS不仅用于毒品纯品的检测,对于复杂体系的缴获毒品和人体检材毒品的检测也逐渐成为研究热点.本文重点总结了SERS检测毒品的种类和方法,介绍了用于毒品检测的增强基底的发展,以及基于SERS的检测技术的进展,并对SERS毒品检测数据的分析方法做了概括.最后讨论了SERS在毒品检测面临的主要挑战,并展望了基于SERS毒品痕量检测的未来发展趋势.     

金属有机框架材料在分离分析领域的研究进展

金属有机框架材料是由金属离子节点和有机配体通过配位键连接形成的具有序多孔骨架的材料, 因其具有比表面积大、 孔隙可调及表面性质可控等优点而备受关注. 通过对有机配体和金属离子进行选择及对金属有机框架材料进行后修饰处理, 可实现对金属有机框架材料表面性质的调控, 以提升其选择性吸附及特异性识别等性能, 进而拓展其在分离分析等领域的应用. 本文从金属有机框架材料的表面性质调控出发, 介绍了其表面性质与分离分析性能的关系, 总结了近年来该领域的代表性工作, 并展望了金属有机框架材料在分离分析领域的应用前景.     

含氟硼二吡咯单元金属有机骨架材料的研究进展

MOFs是一种具有高度有序孔道结构和较大比表面积的材料,而含氟硼二吡咯(BODIPY)发色团的MOFs材料是将BODIPY发色团设计成可与金属中心配位的配体并直接与金属离子配位或将该发色团作为光吸收天线引入到MOFs材料中所制备的材料,此类材料因对可见光有较强的吸收而受到广泛关注。本文总结了含BODIPY发色团MOFs材料的制备方法,探讨了此类材料的结构特点、光物理性质及应用前景,最后展望了未来此类材料的前景和发展趋势。本文可为BODIPY发色团的MOFs材料在光化学领域的发展提供参考。     

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.