Metal-organic frameworks (MOFs) are an emerging class of porous materials with potential applications in gas storage, separations, catalysis, and chemical sensing. Despite numerous advantages, applications of many MOFs are ultimately limited by their stability under harsh conditions. Herein, the recent advances in the field of stable MOFs, covering the fundamental mechanisms of MOF stability, design, and synthesis of stable MOF architectures, and their latest applications are reviewed. First, key factors that affect MOF stability under certain chemical environments are introduced to guide the design of robust structures. This is followed by a short review of synthetic strategies of stable MOFs including modulated synthesis and postsynthetic modifications. Based on the fundamentals of MOF stability, stable MOFs are classified into two categories: high-valency metal-carboxylate frameworks and low-valency metal-azolate frameworks. Along this line, some representative stable MOFs are introduced, their structures are described, and their properties are briefly discussed. The expanded applications of stable MOFs in Lewis/Bronsted acid catalysis, redox catalysis, photocatalysis, electrocatalysis, gas storage, and sensing are highlighted. Overall, this review is expected to guide the design of stable MOFs by providing insights into existing structures, which could lead to the discovery and development of more advanced functional materials.

Stable Metal-Organic Frameworks: Design, Synthesis, and Applications.

Notably, many significant breakthroughs for a new generation of supercapacitors have been reported in recent years, related to theoretical understanding, material synthesis and device designs. Herein, we summarize the state-of-the-art progress toward mechanisms, new materials, and novel device designs for supercapacitors. Firstly, fundamental understanding of the mechanism is mainly focused on the relationship between the structural properties of electrode materials and their electrochemical performances based on some in situ characterization techniques and simulations. Secondly, some emerging electrode materials are discussed, including metal–organic frameworks (MOFs), covalent organic frameworks (COFs), MXenes, metal nitrides, black phosphorus, LaMnO3, and RbAg4I5/graphite. Thirdly, the device innovations for the next generation of supercapacitors are provided successively, mainly emphasizing flow supercapacitors, alternating current (AC) line-filtering supercapacitors, redox electrolyte enhanced supercapacitors, metal ion hybrid supercapacitors, micro-supercapacitors (fiber, plane and three-dimensional) and multifunctional supercapacitors including electrochromic supercapacitors, self-healing supercapacitors, piezoelectric supercapacitors, shape-memory supercapacitors, thermal self-protective supercapacitors, thermal self-charging supercapacitors, and photo self-charging supercapacitors. Finally, the future developments and key technical challenges are highlighted regarding further research in this thriving field.

Latest advances in supercapacitors: from new electrode materials to novel device designs.

Rapidly increasing atmospheric CO2 concentrations threaten human society, the natural environment, and the synergy between the two. In order to ameliorate the CO2 problem, carbon capture and conversion techniques have been proposed. Metal–organic framework (MOF)-based materials, a relatively new class of porous materials with unique structural features, high surface areas, chemical tunability and stability, have been extensively studied with respect to their applicability to such techniques. Recently, it has become apparent that the CO2 capture capabilities of MOF-based materials significantly boost their potential toward CO2 conversion. Furthermore, MOF-based materials’ well-defined structures greatly facilitate the understanding of structure–property relationships and their roles in CO2 capture and conversion. In this review, we provide a comprehensive account of significant progress in the design and synthesis of MOF-based materials, including MOFs, MOF composites and MOF derivatives, and their application to carbon capture and conversion. Special emphases on the relationships between CO2 capture capacities of MOF-based materials and their catalytic CO2 conversion performances are discussed.

Carbon capture and conversion using metal–organic frameworks and MOF-based materials

Metal-organic framework (MOF) nanoparticles, also called porous coordination polymers, are a major part of nanomaterials science, and their role in catalysis is becoming central. The extraordinary variability and richness of their structures afford engineering synergies between the metal nodes, functional linkers, encapsulated substrates, or nanoparticles for multiple and selective heterogeneous interactions and activations in these MOF-based nanocatalysts. Pyrolysis of MOF-nanoparticle composites forms highly porous N- or P-doped graphitized MOF-derived nanomaterials that are increasingly used as efficient catalysts especially in electro- and photocatalysis. This review first briefly summarizes this background of MOF nanoparticle catalysis and then comprehensively reviews the fast-growing literature reported during the last years. The major parts are catalysis of organic and molecular reactions, electrocatalysis, photocatalysis, and views of prospects. Major challenges of our society are addressed using these well-defined heterogeneous catalysts in the fields of synthesis, energy, and environment. In spite of the many achievements, enormous progress is still necessary to improve our understanding of the processes involved beyond the proof-of-concept, particularly for selective methane oxidation, hydrogen production, water splitting, CO2 reduction to methanol, nitrogen fixation, and water depollution.

State of the Art and Prospects in Metal-Organic Framework (MOF)-Based and MOF-Derived Nanocatalysis.

Flexible solid-state supercapacitors (FSSCs) are frontrunners in energy storage device technology and have attracted extensive attention owing to recent significant breakthroughs in modern wearable electronics In this study, we review the state-of-the-art advancements in FSSCs to provide new insights on mechanisms, emerging electrode materials, flexible gel electrolytes and novel cell designs The review begins with a brief introduction on the fundamental understanding of charge storage mechanisms based on the structural properties of electrode materials The next sections briefly summarise the latest progress in flexible electrodes (ie, freestanding and substrate-supported, including textile, paper, metal foil/wire and polymer-based substrates) and flexible gel electrolytes (ie, aqueous, organic, ionic liquids and redox-active gels) Subsequently, a comprehensive summary of FSSC cell designs introduces some emerging electrode materials, including MXenes, metal nitrides, metal–organic frameworks (MOFs), polyoxometalates (POMs) and black phosphorus Some potential practical applications, such as the development of piezoelectric, photo-, shape-memory, self-healing, electrochromic and integrated sensor-supercapacitors are also discussed The final section highlights current challenges and future perspectives on research in this thriving field

Towards flexible solid-state supercapacitors for smart and wearable electronics

Metal-organic frameworks (MOFs) with high surface area and tunable chemical structures have attracted tremendous attention. Recently, there has been increasing interest in deriving advanced materials from MOFs for electrochemical energy storage and conversion. This progress report highlights recent breakthroughs in electrocatalysis by using MOF-based novel catalysts, such as in oxygen reduction and evolution, hydrogen evolution and carbon dioxide reduction. The advantages of preparing electrocatalysts from MOFs are introduced and discussed. Then, the development of MOF derived electrocatalysis-active products, such as heteroatom-doped carbon, metal oxide (MO), metal sulfide (MS), metal carbide (MC), metal phosphide (MP) and their hybrids with carbon, are summarized. The detailed functions of these materials in representative electrocatalysis systems are also reviewed. The demonstrated examples will provide understanding in preparing highly active and stable electrocatalysts. The progress report concludes with the future applications of MOF-based materials in the field of electrocatalysis.

Metal‐Organic Framework‐Based Nanomaterials for Electrocatalysis

Yolk-shell nanostructures have received great attention for boosting the performance of lithium-ion batteries because of their obvious advantages in solving the problems associated with large volume change, low conductivity, and short diffusion path for Li+ ion transport. A universal strategy for making hollow transition metal oxide (TMO) nanoparticles (NPs) encapsulated into B, N co-doped graphitic nanotubes (TMO@BNG (TMO = CoO, Ni2 O3 , Mn3 O4 ) through combining pyrolysis with an oxidation method is reported herein. The as-made TMO@BNG exhibits the TMO-dependent lithium-ion storage ability, in which CoO@BNG nanotubes exhibit highest lithium-ion storage capacity of 1554 mA h g-1 at the current density of 96 mA g-1 , good rate ability (410 mA h g-1 at 1.75 A g-1 ), and high stability (almost 96% storage capacity retention after 480 cycles). The present work highlights the importance of introducing hollow TMO NPs with thin wall into BNG with large surface area for boosting LIBs in the terms of storage capacity, rate capability, and cycling stability.

A Universal Strategy for Hollow Metal Oxide Nanoparticles Encapsulated into B/N Co-Doped Graphitic Nanotubes as High-Performance Lithium-Ion Battery Anodes

DOI: 10.1002/aenm.201601671 easy for the agglomeration under high current and long-term testing for HER, which showed poor stability and exhibited low HER activity irrespective of pH value.[7] Recently, researchers employed carbon shell to protect the metal or their compounds NPs from acidic atmospheric degradation and agglomeration with neighboring NPs.[8] These new metal/carbon composites not only enabled the catalytic applications of metal NPs which are also not stable as the naked in ambient atmosphere, but also improved their electron transport to certain extent. However, if the carbon layers on active species are too thick or with low porosity, it could hinder the desired access of mass transport, and as a result catalytic activity of metal is significantly decreased.[9] In this regard, recently developed in situ technology to prepare metal@carbon by using metal–organic frameworks (MOFs) as precursors has highlighted new functionality for such application.[10] MOFs are crystalline regular porous materials prepared by the coupling of metal ions with organic linkers,[11] and their derived composites, like nitrogendoped porous carbon, exhibit large surface area and hierarchical pore structures, which play important roles to ample the various catalytic reactions, such as HER, oxygen reduction, and evolution reaction.[12] However, such kind of materials consisted of some low degree of graphitization and poor bonding interactions between active metal NPs and derived carbon.[13] To improve the electron transport and valid mass diffusion path for HER, we apply this concept by using B/N co-doped graphene (BCN) nanotubes to confine MOF-derived CoP NPs. Furthermore, it is well documented that chemical replacement of carbon atom by nitrogen (N) and boron (B) can modulate the charge polarization of carbon nanotubes.[14] In particular, the two elements are reverse in electronegativity to that of carbon as B and N co-doping could activate the electron spin density between heteroatom and adjacent carbon atom. Thus, synergistic effect of ternary system of BCN nanotubes greatly enlarges the catalytic surface area.[14a,15] Meanwhile, it is anticipated that co-doping of B and N in graphene nanotubes encapsulated metal phosphide NPs will not only prevent the agglomeration of metal but also produce the additional active sites to enhance the HER performance. To the best of our knowledge, encapsulation of metal phosphide NPs in heteroatom graphitic nanotubes is a challenging task and has rarely been reported. Herein, we introduce a bottom-up strategy for synthesis of CoP architecture encapsulated into BCN nanotubes (CoP@BCN) through pyrolysis and phosphidation as shown in Owing to the increasing worldwide concern over energy crisis and environmental issues, great attention has been triggered for the development of clean and highly efficient energy conversion and storage techniques by electrocatalytic reaction in recent years.[1] As a promising candidate for the future energy supply, molecular hydrogen (H2) possess the highest gravimetric energy density and produced from electrocatalytic water splitting. The highly efficient electrocatalysts are crucial for lower overpotential to improve the energy transfer efficiency in hydrogen evolution reaction (HER).[2] Traditionally, rare earth metal Pt has been regarded as the best electrocatalyst to accelerate the kinetics in HER which is a prerequisite.[3] Unfortunately, their commercial applications are impeded by high cost and scarcity.[4] A key strategy to replace the precious Pt catalyst with earth abundant metals would promote global scalability of such potential clean energy applications.[5] Thus motivated by these several challenges, the search for a cost-effective, large earth abundant, highly efficient, and long stability has been made of immense significance toward earth-enriched metal for HER electrocatalysts. Recently, transition metal phosphide (TMP) based electrocatalysts have been broadly applied for HER activity.[5] Among the existing myriad of TMP, cobalt phosphide (CoP) has been identified as a promising candidate for HER as compared to iron, copper, nickel, and tungsten phosphides.[6] It has been identified that phosphorus (P) atom insertion into cobalt crystal lattice plays a crucial role for HER performance, because P atoms with more electronegativity can grab electron from metal atoms and act as a proton carrier.[2c] Nevertheless, the higher concentration of P in TMP restricts the delocalization of the metal atoms and impede the electron transportation which discards the HER activity.[6f ] Besides this, these electrocatalysts with certain morphologies of nanoparticles (NPs) or nanowires (NWs) are

Metal–Organic Frameworks Derived Cobalt Phosphide Architecture Encapsulated into B/N Co-Doped Graphene Nanotubes for All pH Value Electrochemical Hydrogen Evolution

Metal–organic frameworks (MOFs) have emerged as desirable cross-functional platforms for electrochemical and photochemical energy conversion and storage (ECS) systems owing to their highly ordered ...

Metal–Organic Framework-Based Materials for Energy Conversion and Storage

Hierarchically porous electrodes made of electrochemically active materials and conductive additives may display synergistic effects originating from the interactions between the constituent phases, and this approach has been adopted for optimizing the performances of many electrode materials. Here we report our findings in design, fabrication, and characterization of a hierarchically porous hybrid electrode composed of α-NiS nanorods decorated on reduced graphene oxide (rGO) (denoted as R-NiS/rGO), derived from water-refluxed metal–organic frameworks/rGO (Ni-MOF-74/rGO) templates. Microanalyses reveal that the as-synthesized α-NiS nanorods have abundant (101) and (110) surfaces on the edges, which exhibit a strong affinity for OH− in KOH electrolyte, as confirmed by density functional theory-based calculations. The results suggest that the MOF-derived α-NiS nanorods with highly exposed active surfaces are favorable for fast redox reactions in a basic electrolyte. Besides, the presence of rGO in the hybrid electrode greatly enhances the electronic conductivity, providing efficient current collection for fast energy storage. Indeed, when tested in a supercapacitor with a three-electrode configuration in 2 M KOH electrolyte, the R-NiS/rGO hybrid electrode exhibits a capacity of 744 C g−1 at 1 A g−1 and 600 C g−1 at 50 A g−1, indicating remarkable rate performance, while maintaining more than 89% of the initial capacity after 20 000 cycles. Moreover, when coupled with a nitrogen-doped graphene aerogel (C/NG-A) negative electrode, the hybrid supercapacitor (R-NiS/rGO/electrolyte/C/NG-A) achieved an ultra-high energy density of 93 W h kg−1 at a power density of 962 W kg−1, while still retaining an energy density of 54 W h kg−1 at an elevated working power of 46 034 W kg−1.

Hassina Tabassum

Papers

Metal‐Organic Framework‐Based Nanomaterials for Electrocatalysis

A Universal Strategy for Hollow Metal Oxide Nanoparticles Encapsulated into B/N Co-Doped Graphitic Nanotubes as High-Performance Lithium-Ion Battery Anodes

Metal–Organic Frameworks Derived Cobalt Phosphide Architecture Encapsulated into B/N Co-Doped Graphene Nanotubes for All pH Value Electrochemical Hydrogen Evolution

Metal–Organic Framework-Based Materials for Energy Conversion and Storage

MOF-derived α-NiS nanorods on graphene as an electrode for high-energy-density supercapacitors