Pore‐Environment Engineering with Multiple Metal Sites in Rare‐Earth Porphyrinic Metal–Organic Frameworks

Multi‐component metal–organic frameworks (MOFs) with precisely controlled pore environments are highly desired owing to their potential applications in gas adsorption, separation, cooperative catalysis, and biomimetics. A series of multi‐component MOFs, namely PCN‐900(RE), were constructed from a combination of tetratopic porphyrinic linkers, linear linkers, and rare‐earth hexanuclear clusters (RE₆) under the guidance of thermodynamics. These MOFs exhibit high surface areas (up to 2523 cm² g^?1) and unlimited tunability by modification of metal nodes and/or linker components. Post‐synthetic exchange of linear linkers and metalation of two organic linkers were realized, allowing the incorporation of a wide range of functional moieties. Two different metal sites were sequentially placed on the linear linker and the tetratopic porphyrinic linker, respectively, giving rise to an ideal platform for heterogeneous catalysis.     

Synthetic strategies for chiral metal-organic frameworks

By direct synthesis route, chiral metal-organic frameworks are synthetized with enantiopure ligands or spontaneous resolution; by indirect method, post-synthetic method and chiral inductionare introduced to construct chiral metal-organic frameworks.     

Active-site-accessible, porphyrinic metal-organic framework materials

On account of their structural similarity to cofactors found in many metallo-enzymes, metalloporphyrins are obvious potential building blocks for catalytically active, metal-organic framework (MOF) materials. While numerous porphyrin-based MOFs have already been described, versions featuring highly accessible active sites and permanent microporosity are remarkably scarce. Indeed, of the more than 70 previously reported porphyrinic MOFs, only one has been shown to be both permanently microporous and contain internally accessible active sites for chemical catalysis. Attempts to generalize the design approach used in this single successful case have failed. Reported here, however, is the synthesis of an extended family of MOFs that directly incorporate a variety of metalloporphyrins (specifically Al(3+), Zn(2+), Pd(2+), Mn(3+), and Fe(3+) complexes). These robust porphyrinic materials (RPMs) feature large channels and readily accessible active sites. As an illustrative example, one of the manganese-containing RPMs is shown to be catalytically competent for the oxidation of alkenes and alkanes.     

Stimulus‐Responsive Metal–Organic Frameworks

Materials that can recognize the changes in their local environment and respond by altering their inherent physical and/or chemical properties are strong candidates for future “smart” technology materials. Metal–organic frameworks (MOFs) have attracted a great deal of attention in recent years owing to their designable architecture, host–guest chemistry, and softness as porous materials. Despite this fact, studies on the tuning of the properties of MOFs by external stimuli are still rare. This review highlights the recent developments in the field of stimulus‐responsive MOFs or so‐called smart MOFs. In particular, the various stimuli used and the utility of stimulus‐responsive smart MOFs for various applications such as gas storage and separation, sensing, clean energy, catalysis, molecular motors, and biomedical applications are highlighted by using representative examples. Future directions in the developments of stimulus‐responsive smart MOFs and their applications are proposed from a personal perspective.     

A roadmap to implementing metal-organic frameworks in electronic devices: challenges and critical directions

Metal-organic frameworks (MOFs) and related material classes are attracting considerable attention for applications such as gas storage, separations, and catalysis. In contrast, research focused on potential uses in electronic devices is in its infancy. Several sensing concepts in which the tailorable chemistry of MOFs is used to enhance sensitivity or provide chemical specificity have been demonstrated, but in only a few cases are MOFs an integral part of an actual device. The synthesis of a few electrically conducting MOFs and their known structural flexibility suggest that MOF-based electronic devices exploiting these properties could be constructed. It is clear, however, that new fabrication methods are required to take advantage of the unique properties of MOFs and extend their use to the realms of electronic circuitry. In this Concepts article, we describe the basic functional elements needed to fabricate electronic devices and summarize the current state of relevant MOF research, and then review recent work in which MOFs serve as active components in electronic devices. Finally, we propose a high-level roadmap for device-related MOF research, the objective of which is to stimulate thinking within the MOF community concerning the development these materials for applications including sensing, photonics, and microelectronics.     

Current Trend in Synthesis,Post‐Synthetic Modifications and Biological Applications of Nanometal‐Organic Frameworks (NMOFs)

Since the early reports of MOFs and their interesting properties, research involving these materials has grown wide in scope and applications. Various synthetic approaches have ensued in view of obtaining materials with optimised properties, the extensive scope of application spanning from energy, gas sorption, catalysis biological applications has meant exponentially evolved over the years. The far‐reaching synthetic and PSM approaches and porosity control possibilities have continued to serve as a motivation for research on these materials. With respect to the biological applications, MOFs have shown promise as good candidates in applications involving drug delivery, BioMOFs, sensing, imaging amongst others. Despite being a while away from successful entry into the market, observed results in sensing, drug delivery, and imaging put these materials on the spot light as candidates poised to usher in a revolution in biology. In this regard, this review article focuses current approaches in synthesis, post functionalization and biological applications of these materials with particular attention on drug delivery, imaging, sensing and BioMOFs.     

2D Porphyrinic Metal-Organic Frameworks Featuring Rod-Shaped Secondary Building Units

Metal-organic frameworks (MOFs) encompass a rapidly expanding class of materials with diverse potential applications including gas storage, molecular separation, sensing and catalysis. So-called ‘rod MOFs’, which comprise infinitely extended 1D secondary building units (SBUs), represent an underexplored subclass of MOF. Further, porphyrins are considered privileged ligands for MOF synthesis due to their tunable redox and photophysical properties. In this study, the Cu^II complex of 5,15-bis(4-carboxyphenyl)-10,20-diphenylporphyrin (H₂L-Cu^II, where H₂ refers to the ligand’s carboxyl H atoms) is used to prepare two new 2D porphyrinic rod MOFs PROD-1 and PROD-2. Single-crystal X-ray analysis reveals that these frameworks feature 1D Mn^II- or Co^II-based rod-like SBUs that are coordinated by labile solvent molecules and photoactive porphyrin moieties. Both materials were characterised using infrared (IR) spectroscopy, powder X-ray diffraction (PXRD) spectroscopy and thermogravimetric analysis (TGA). The structural attributes of PROD-1 and PROD-2 render them promising materials for future photocatalytic investigations.     

Porous metal-organic frameworks as platforms for functional applications

Metal-organic frameworks (MOFs), also known as coordination polymers, have emerged as a new class of crystalline porous materials, which are constructed from metal ions or metal ion clusters and bridging organic linkers. MOFs have tunable pores and functionalities, and usually exhibit very high surface areas. The potential applications of porous MOFs cover a broad range of fields and most of their applications are related to pore sizes, shapes and structures/environments. In this feature article, we provide an overview of the recent developments of porous MOFs as platforms in the functional applications of sorption and separation, heterogeneous catalysis, as supports/host matrices for metal nanoparticles, and as templates/nanoreactors for new material preparation.     

氨基功能化金属有机骨架光催化剂的制备及性能研究

氨基功能化金属有机骨架材料(Metal-organic frameworks,MOFs)是一种非常具有吸引力的功能化MOFs,其兼具MOFs的高比表面积、孔道易调控及氨基的可后处理修饰的性能。通过简单的化学反应可实现功能基团的转化,从而制得新型的功能化MOFs,在气体存储、药物载体、选择性吸附气体小分子和催化等领域具有潜在的应用价值,因此开发氨基功能化的MOFs备受人们关注。本文综述了近年来氨基功能化MOFs在催化和吸附领域的研究进展,包括氨基功能化MOFs的制备方法、影响因素以及在环境方面的应用,并对今后的发展前景进行了展望。     

Mixed‐Metal MOFs: Unique Opportunities in Metal–Organic Framework (MOF) Functionality and Design

Mixed‐metal metal–organic frameworks (MM‐MOFs) can be considered to be those MOFs having two different metals anywhere in the structure. Herein we summarize the various strategies for the preparation of MM‐MOFs and some of their applications in adsorption, gas separation, and catalysis. It is shown that compared to homometallic MOFs, MM‐MOFs bring about the opportunity to take advantage of the complexity and the synergism derived from the presence of different metal ions in the structure of MOFs. This is reflected in a superior performance and even stability of MM‐MOFs respect to related single‐metal MOFs. Emphasis is made on the use of MM‐MOFs as catalysts for tandem reactions.     

Impact of Higher‐Order Structuralization on the Adsorptive Properties of Metal–Organic Frameworks

The structural processing of metal–organic frameworks (MOFs) over multiple length scales is critical for their successful use as adsorbents in a variety of emerging applications. Although significant advances in molecular‐scale design have provided strategies to boost the adsorptive capacities of MOFs, relatively little attention has been directed toward understanding the influence of higher‐order structuralization on the material performance. Herein, we present the main strategies that are currently available for the structural processing of MOFs and discuss the influence these processes can impart on the adsorptive properties of the materials. In all, this intriguing area of research is expected to provide significant opportunities to enhance the properties of MOFs further, which will ultimately aid in their optimization in the context of specific real‐world applications.     

Probing the Interactions of Porphyrins with Macromolecules Using NMR Spectroscopy Techniques

Porphyrinic compounds are widespread in nature and play key roles in biological processes such as oxygen transport in blood, enzymatic redox reactions or photosynthesis. In addition, both naturally derived as well as synthetic porphyrinic compounds are extensively explored for biomedical and technical applications such as photodynamic therapy (PDT) or photovoltaic systems, respectively. Their unique electronic structures and photophysical properties make this class of compounds so interesting for the multiple functions encountered. It is therefore not surprising that optical methods are typically the prevalent analytical tool applied in characterization and processes involving porphyrinic compounds. However, a wealth of complementary information can be obtained from NMR spectroscopic techniques. Based on the advantage of providing structural and dynamic information with atomic resolution simultaneously, NMR spectroscopy is a powerful method for studying molecular interactions between porphyrinic compounds and macromolecules. Such interactions are of special interest in medical applications of porphyrinic photosensitizers that are mostly combined with macromolecular carrier systems. The macromolecular surrounding typically stabilizes the encapsulated drug and may also modify its physical properties. Moreover, the interaction with macromolecular physiological components needs to be explored to understand and control mechanisms of action and therapeutic efficacy. This review focuses on such non-covalent interactions of porphyrinic drugs with synthetic polymers as well as with biomolecules such as phospholipids or proteins. A brief introduction into various NMR spectroscopic techniques is given including chemical shift perturbation methods, NOE enhancement spectroscopy, relaxation time measurements and diffusion-ordered spectroscopy. How these NMR tools are used to address porphyrin–macromolecule interactions with respect to their function in biomedical applications is the central point of the current review.     

功能金属-有机骨架材料的应用

金属有机骨架（Metal-Organic Framework,MOFs）材料由于其特殊的结构引起了科学家的广泛关注,它作为多孔材料与无机或有机的多孔材料相比具有特殊的优势,是目前新功能材料研究领域的一个热点。本文总结了金属有机骨架多孔材料在分离纯化、催化、微反应器、负离子交换、复合功能材料等方面的应用进展,并对这种新型多功能材料在设计、合成与应用方面的广阔前景作了展望。     

Metal Organic Frameworks for Bioelectrochemical Applications

Metal organic frameworks (MOFs) with their high pore volumes and chemically-diverse pore environments have emerged as components of catalytic electrodes for biosensors, biofuel cells, and bioreactors. MOFs are widely exploited for gas capture, separations, and catalysis, but their integration at electrodes with biocatalysts for (bio)electrocatalysis is a niche topic that remains largely unexplored. This review focuses on recent advances in MOF and MOF-derived carbon electrodes for bioelectrochemical applications. A range of MOF materials and their integration into devices with enzymes and microbes are reported. Key properties and performance characteristics are considered and opportunities facing MOFs for (bio)electrochemical applications are discussed.     

Identifying promising metal–organic frameworks for heterogeneous catalysis via high-throughput periodic density functional theory

Metal–organic frameworks (MOFs) are a class of nanoporous materials with highly tunable structures in terms of both chemical composition and topology. Due to their tunable nature, high-throughput computational screening is a particularly appealing method to reduce the time-to-discovery of MOFs with desirable physical and chemical properties. In this work, a fully automated, high-throughput periodic density functional theory (DFT) workflow for screening promising MOF candidates was developed and benchmarked, with a specific focus on applications in catalysis. As a proof-of-concept, we use the high-throughput workflow to screen MOFs containing open metal sites (OMSs) from the Computation-Ready, Experimental MOF database for the oxidative C—H bond activation of methane. The results from the screening process suggest that, despite the strong C—H bond strength of methane, the main challenge from a screening standpoint is the identification of MOFs with OMSs that can be readily oxidized at moderate reaction conditions. © 2019 Wiley Periodicals, Inc.     

Metal-organic framework growth at functional interfaces: thin films and composites for diverse applications

Porous metal-organic frameworks (MOFs) are highly ordered crystalline materials prepared by the self-assembly of metal ions with organic linkers to yield low density network structures of diverse topology. MOFs have attracted considerable attention over the last decade due to their facile preparation, tunable pore metrics and the ease of functionalisation of their internal surfaces, such that designer frameworks with exceptional properties for application in gas-storage, separation of small molecules, heterogeneous catalysis and drug delivery are becoming commonplace. For any material to find practical utility however, there is a need for processing and formulation into application-specific configurations. One way to do this is to prepare composite materials where the MOF is supported on a planar substrate or some other shaped body through interaction with functional groups at the support interface. This is a rapidly developing research area, and this review provides an overview of the diverse MOF composite materials prepared up to now, organised by interface type. The importance of the interface is explored within each section and while the overall emphasis is on applications of the composites, coatings and MOF-based devices, the most widely-used and successful synthetic strategies for composite formation are also presented. (183 references).     

Electrically Conductive Porous Metal–Organic Frameworks

Owing to their outstanding structural, chemical, and functional diversity, metal–organic frameworks (MOFs) have attracted considerable attention over the last two decades in a variety of energy‐related applications. Notably missing among these, until recently, were applications that required good charge transport coexisting with porosity and high surface area. Although most MOFs are electrical insulators, several materials in this class have recently demonstrated excellent electrical conductivity and high charge mobility. Herein we review the synthetic and electronic design strategies that have been employed thus far for producing frameworks with permanent porosity and long‐range charge transport properties. In addition, key experiments that have been employed to demonstrate electrical transport, as well as selected applications for this subclass of MOFs, will be discussed.     

Effect of Topology on Photodynamic Sterilization of Porphyrinic Metal-Organic Frameworks

Porphyrinic metal-organic frameworks (MOFs) are promising photosensitizers due to the lack of self-aggregation of porphyrin in aqueous solution. However, how the topology of porphyrinic MOFs affects the generation of singlet oxygen (¹O₂) is unclear. Here, the effect of the topology of porphyrinic MOFs on their photodynamic performance is reported. Four porphyrinic zirconium MOFs (MOF-525, MOF-545, PCN-223 and PCN-224 with different topologies: ftw , csq , shp and she , respectively) were selected to study the influence of topology on the photodynamic antibacterial performance. The ¹O₂ generation and the photodynamic antibacterial performance followed an decreasing order of MOF-545>MOF-525>PCN-224>PCN-223. The results reveal that the pore size, the distance between porphyrin, and the number of porphyrin per Zr₆O₈ cluster in MOFs greatly affected ¹O₂ generation. This work provides guidance for designing new MOFs for efficient photodynamic sterilization.     

Homochiral porous metal-organic frameworks: Why and how?

This paper highlights the most significant recent advances in the synthesis, characterization, and applications of single-crystalline homochiral porous metal-organic frameworks (MOFs). The motivations for the synthesis of homochiral porous solids and the strategies on how they can be designed are provided. The latest examples of chiral separation and Lewis acid heterogeneous asymmetric catalysis using homochiral porous MOFs are presented.     

Engineering Metal–Organic Framework Catalysts for C−C and C−X Coupling Reactions: Advances in Reticular Approaches from 2014–2018

Metal–organic frameworks (MOFs) are a class of crystalline porous materials that have been actively used for several industrial and synthetic applications. MOFs are spatially and geometrically extrapolated coordination polymers with intriguing properties such as tunable porosity and dimensionality. In terms of their catalytic efficiency, MOFs combine the easy recoverability of heterogeneous catalysts with the increased selectivity of biological catalysts. It is therefore not surprising that a lot of work on optimizing MOF catalysts for organic transformations has been carried out over the past decade. In this review, recent developments in MOF catalysis are summarized, with special attention being paid to C−C, C−N, and C−O coupling reactions. The influence of pore size, pore environment, and load on catalytic activity is described. Post-synthetic stabilization techniques and host–guest interactions in caged MOF scaffolds are detailed. Mechanistic aspects pertaining to the use of MOFs in asymmetric heterogeneous catalysis are highlighted and categorized.