Fabrication of carbon nanorods and graphene nanoribbons from a metal–organic framework

Puffing Up Energetic Metal-Organic Frameworks to Large Carbon Networks with Hierarchical Porosity and Atomically Dispersed Metal Sites

Large carbon networks featuring hierarchical pores and atomically dispersed metal sites (ADMSs) are ideal materials for energy storage and conversion due to the spatially continuous conductive networks and highly active ADMSs. However, it is a challenge to synthesize such ADMS-decorated carbon networks. Here, an innovative fusion-foaming methodology is presented in which energetic metal-organic framework (EMOF) nanoparticles are puffed up to submillimeter-scaled ADMS-decorated carbon networks via a one-step pyrolysis. Their extraordinary catalytic performance towards oxygen reduction reaction verifies the practicability of this synthetic approach. Moreover, this approach can be readily applicable to a wide range of unexplored EMOFs, expanding scopes for future materials design.

π-Conjugated Molecule Boosts Metal-Organic Frameworks as Efficient Oxygen Evolution Reaction Catalysts

To improve the efficiency of water electrolysis, developing efficient oxygen evolution reaction (OER) electrocatalysis is extremely important due to its four-electron transfer dynamics. In this work, a π-conjugated molecule (2,3,6,7,10,11-hexahydroxytriphenylene, HHTP), which can accelerate the electron transfer, is coated directly on pristine ZIF-67, resulting in a composite named HHTP@ZIF-67, via a simple one-step solvothermal method. The obtained HHTP@ZIF-67 possesses a Brunauer-Emmett-Teller surface area of 2013.9 m² g^-1 and displays microporous behavior, which can provide enough active sites for OER. The double-layer capacitance of HHTP@ZIF-67 is also enhanced, corresponding to an enlarged electrochemical active surface area. HHTP@ZIF-67 presents a quite low overpotential of 238 mV at 10 mA cm^-2 in 1.0 m KOH. This material synthesized via the simple coating strategy is promising in the application of energy conversion devices.

Two-Dimensional NiSe2/N-Rich Carbon Nanocomposites Derived from Ni-Hexamine Frameworks for Superb Na-Ion Storage

Design of functional carbon-based nanomaterials from metal-organic frameworks (MOFs) has attracted soaring interests in recent years. However, a MOF-derived strategy toward two-dimensional (2D) nanomaterials remains a great challenge. In this work, we develop a layered Ni-hexamine framework as efficient precursor to prepare a 2D NiSe₂/N-rich carbon nanocomposite by a simple pyrolysis and subsequent selenization process. In the 2D NiSe₂/N-rich carbon nanocomposite, NiSe₂ nanoparticles with diameters of ca. 75 nm are homogeneously distributed in the N-rich carbon nanosheets. When serving as anode materials for sodium-ion batteries, the 2D nanocomposites exhibit a high reversible capacity of 410 mAh g^-1 at 1 A g^-1 and maintain a value of 255 mAh g^-1 even at 10 A g^-1. The excellent electrochemical performance can be attributed to the synergistic effects between the N-rich carbon nanosheets and NiSe₂ nanoparticles. More importantly, the hexamine-based MOFs can be regarded as new and powerful platforms for the fabrication of 2D N-rich carbon-based nanomaterials, which is of great importance for various potential applications.

Six Isomorphous Window-Beam MOFs: Explore the Effects of Metal Ions on MOF-Derived Carbon for Supercapacitors

Six isomorphous metal-organic frameworks (MOFs) with a 3D window-beam architecture have been synthesized from solvothermal reactions, and are named Zn, Cd, Ni, Co, Mn and Cu-MOF, respectively. The series of MOFs was utilized as precursors to synthesize MOF-derived carbon with different morphologies. Zn and Cd-MOFs lead to the derivation of porous carbons (PCs), which exhibit remarkable BET specific surface areas. For derivates of Ni, Co and Mn-MOFs, graphitized carbons (GCs) show some carbon graphitization, but their BET specific surface areas are relatively small. C-Cu has the smallest BET specific surface area, and there is no carbon graphitization. Therefore, the metal ion of the parent MOF exerts a crucial effect on the preparation of MOF-derived carbon, such as the pore-forming effect of Zn and Cd species, and catalytic graphitization of Ni, Co, and Mn species. The capacitances of MOF-derived carbon follow the sequence of PCs>GCs>C-Cu, which reveals that the specific surface area plays a dominant role in the capacitive performance of electrical double layer capacitors (EDLCs), and that the graphitization could improve the capacitance. Significantly, PC-Zn exhibits the best specific capacitance (138 F g^-1 at 0.5 Ag^-1 ), and excellent life cycle, which can be applied as an electrode material in supercapacitors.

Perspective to the Potential Use of Graphene in Li-Ion Battery and Supercapacitor

Graphene is a hot star in materials science with various potential application aspects, including in Li-ion battery and supercapacitor. The burst of scientific papers in this area seems to validate the performance of graphene, but also arouses large dispute. Herein, we share our judgment of these trends to all, encouraging the discussion and enhancing the understanding of the structure-performance relationship of graphene.

Cobalt-based nanoparticles prepared from MOF-carbon templates as efficient hydrogenation catalysts

Pyrolysis of cobalt-terephthalic acid MOF template on carbon produces highly active and selective cobalt nanoparticles-based hydrogenation catalysts.

The development of efficient and selective nanostructured catalysts for industrially relevant hydrogenation reactions continues to be an actual goal of chemical research. In particular, the hydrogenation of nitriles and nitroarenes is of importance for the production of primary amines, which constitute essential feedstocks and key intermediates for advanced chemicals, life science molecules and materials. Herein, we report the preparation of graphene shell encapsulated Co₃O₄- and Co-nanoparticles supported on carbon by the template synthesis of cobalt-terephthalic acid MOF on carbon and subsequent pyrolysis. The resulting nanoparticles create stable and reusable catalysts for selective hydrogenation of functionalized and structurally diverse aromatic, heterocyclic and aliphatic nitriles, and as well as nitro compounds to primary amines (>65 examples). The synthetic and practical utility of this novel non-noble metal-based hydrogenation protocol is demonstrated by upscaling several reactions to multigram-scale and recycling of the catalyst.

Metal-Organic Frameworks for Separation

Separation is an important industrial step with critical roles in the chemical, petrochemical, pharmaceutical, and nuclear industries, as well as in many other fields. Although much progress has been made, the development of better separation technologies, especially through the discovery of high-performance separation materials, continues to attract increasing interest due to concerns over factors such as efficiency, health and environmental impacts, and the cost of existing methods. Metal-organic frameworks (MOFs), a rapidly expanding family of crystalline porous materials, have shown great promise to address various separation challenges due to their well-defined pore size and unprecedented tunability in both composition and pore geometry. In the past decade, extensive research is performed on applications of MOF materials, including separation and capture of many gases and vapors, and liquid-phase separation involving both liquid mixtures and solutions. MOFs also bring new opportunities in enantioselective separation and are amenable to morphological control such as fabrication of membranes for enhanced separation outcomes. Here, some of the latest progress in the applications of MOFs for several key separation issues, with emphasis on newly synthesized MOF materials and the impact of their compositional and structural features on separation properties, are reviewed and highlighted.

Well-dispersed Ni or MnO nanoparticles on mesoporous carbons: preparation via carbonization of bimetallic MOF-74s for highly reactive redox catalysts

A series of metal-organic framework-74s (MOF-74s), composed of two different metallic species (Zn/Ni or Zn/Mn in various compositions), were synthesized, and Ni or MnO-doped carbonaceous materials were first prepared by pyrolysis of the MOFs under an inert environment for catalytic applications. These MOF-derived nanomaterials (MDNMs), obtained by pyrolysis of MOF-74s, were characterized thoroughly to understand their phase, porosity, particle size, dispersion, and composition. With increasing Zn content in the bimetallic MOF-74s, the porosity of the MDNMs increased but the size and content of Ni or MnO in the MDNMs decreased monotonously. One MDNM(75Zn25Mn), prepared from MOF-74(75%Zn/25%Mn), showed noticeably higher activity in the oxidation of benzyl alcohol as compared with not only the MDNM(xZnyMn)s but also MnOx-loaded carbon or loaded γ-alumina (or, MDNM(75Zn25Mn) showed ∼54 times turnover frequency (TOF) to that of MnO/activated carbon). MDNM(75Zn25Mn) was also effective in the oxidative removal of dibenzothiophene from a model fuel. Moreover, MDNM(75Zn25Ni), prepared from MOF-74(75%Zn/25%Ni), had the highest TOF in the reduction of 4-nitrophenol among various MDNM(xZnyNi)s. The highest activity of MDNM(75Zn25Mn) and MDNM(75Zn25Ni), even with the lowest Mn and Ni contents in the respective MDNMs, for oxidation and reduction in several cycles might be due to the well-dispersed MnO (and Ni) and high porosity with mesopores. Therefore, it can be suggested that pyrolysis of mixed-metal MOFs such as MOF-74s can be a facile way to obtain highly effective and recyclable heterogeneous catalysts, with well-dispersed active species in very small sizes, for various organic reactions.

Metallic Cobalt-Carbon Composite as Recyclable and Robust Magnetic Photocatalyst for Efficient CO2 Reduction

CO2 conversion into value-added chemical fuels driven by solar energy is an intriguing approach to address the current and future demand of energy supply. Currently, most reported surface-sensitized heterogeneous photocatalysts present poor activity and selectivity under visible light irradiation. Here, photosensitized porous metallic and magnetic 1200 CoC composites (PMMCoCC-1200) are coupled with a [Ru(bpy)3 ]Cl2 photosensitizer to efficiently reduce CO2 under visible-light irradiation in a selective and sustainable way. As a result, the CO production reaches a high yield of 1258.30 µL with selectivity of 64.21% in 6 h, superior to most reported heterogeneous photocatalysts. Systematic investigation demonstrates that the central metal cobalt is the active site for activating the adsorbed CO2 molecules and the surficial graphite carbon coating on cobalt metal is crucial for transferring the electrons from the triplet metal-to-ligand charge transfer of the photosensitizer Ru(bpy)32+ , which gives rise to significant enhancement for CO2 reduction efficiency. The fast electron injection from the excited Ru(bpy)32+ to PMMCoCC-1200 and the slow backward charge recombination result in a long-lived, charge-separated state for CO2 reduction. More impressively, the long-time stability and easy magnetic recycling ability of this metallic photocatalyst offer more benefits to the photocatalytic field.

Dandelion-like nickel/cobalt metal-organic framework based electrode materials for high performance supercapacitors

Metal-organic frameworks (MOFs), serving as a promising electrode material in the supercapacitors, have attracted tremendous interests in recent years. Here, through modifying the molar ratio of the Ni²⁺ and Co²⁺, we have successfully fabricated Ni-MOF and Ni/Co-MOF by a facile hydrothermal method. The Ni/Co-MOF with a dandelion-like hollow structure shows an excellent specific capacitance of 758 F g^-1 at 1 A g^-1 in the three-electrode system. Comparing with Ni-MOF, the obtained Ni/Co-MOF has a better rate capacitance (89% retention at 10 A g^-1) and cycling life (75% retention after 5000 circulations). Besides, the assembled asymmetric supercapacitor based on Ni/Co-MOF and active carbon exhibits a high specific energy density of 20.9 W h kg^-1 at the power density of 800 W kg^-1. All these results demonstrate that the mixed-metal strategy is an effective way to optimize the morphology and improve the electrochemical property of the MOFs.

Transition metal-assisted carbonization of small organic molecules toward functional carbon materials

Nanostructured carbon materials with large surface area and desired chemical functionalities have been attracting considerable attention because of their extraordinary physicochemical properties and great application potentials in catalysis, environment, and energy storage. However, the traditional approaches to fabricating these materials rely greatly on complex procedures and specific precursors. We present a simple, effective, and scalable strategy for the synthesis of functional carbon materials by transition metal-assisted carbonization of conventional small organic molecules. We demonstrate that transition metals can promote the thermal stability of molecular precursors and assist the formation of thermally stable polymeric intermediates during the carbonization process, which guarantees the successful preparation of carbons with high yield. The versatility of this synthetic strategy allows easy control of the surface chemical functionality, porosity, and morphology of carbons at the molecular level. Furthermore, the prepared carbons exhibit promising performance in heterogeneous catalysis and electrocatalysis.

Bifunctional Electrocatalysts for Overall Water Splitting from an Iron/Nickel-Based Bimetallic Metal-Organic Framework/Dicyandiamide Composite

Pyrolysis of a bimetallic metal-organic framework (MIL-88-Fe/Ni)-dicyandiamide composite yield a Fe and Ni containing carbonaceous material, which is an efficient bifunctional electrocatalyst for overall water splitting. FeNi₃ and NiFe₂ O₄ are found as metallic and metal oxide compounds closely embedded in an N-doped carbon-carbon nanotube matrix. This hybrid catalyst (Fe-Ni@NC-CNTs) significantly promotes the charge transfer efficiency and restrains the corrosion of the metallic catalysts, which is shown in a high OER and HER activity with an overpotential of 274 and 202 mV, respectively at 10 mA cm^-2 in alkaline solution. When this bifunctional catalyst was further used for H₂ and O₂ production in an electrochemical water-splitting unit, it can operate in ambient conditions with a competitive gas production rate of 1.15 and 0.57 μL s^-1 for hydrogen and oxygen, respectively, showing its potential for practical applications.

One-pot synthesis of a metal-organic framework-based drug carrier for intelligent glucose-responsive insulin delivery

We have developed a glucose-responsive metal-organic framework (MOF)-based insulin delivery nanosystem via a one-pot process. The system relies on the MOF response to glucose stimulation and this can promote insulin delivery. This nanosystem was successfully applied for glucose-responsive and self-regulated insulin release.

Self-template construction of nanoporous carbon nanorods from a metal-organic framework for supercapacitor electrodes

The morphologies and structures of nanostructured carbons generally influence their catalysis, electrochemical performance and adsorption properties. Metal-organic framework (MOF) nanocrystals usually have various morphologies, and can be considered as a template to construct nanostructured carbons with shaped nanocubes, nanorods, and hollow particles by thermal transformation. However, thermal carbonization of MOFs usually leads to collapse of MOF structures. Here, we report shape-preserved carbons (termed as CNRods) by thermal transformation of nickel catecholate framework (Ni-CAT) nanorods. Supercapacitors of CNRods treated at 800 °C were demonstrated to have enhanced performance due to their structural features that facilitate electron conduction and ion transport as well as abundant O content benefiting the wettability of the carbon materials. This may provide a potential way to explore novel carbon materials for supercapacitors with controllable morphologies and high capacitive performance.

"One-for-All" Strategy in Fast Energy Storage: Production of Pillared MOF Nanorod-Templated Positive/Negative Electrodes for the Application of High-Performance Hybrid Supercapacitor

Currently, metal-organic frameworks (MOFs) are intensively studied as active materials for electrochemical energy storage applications due to their tunable structure and exceptional porosities. Among them, water stable pillared MOFs with dual ligands have been reported to exhibit high supercapacitor (SC) performance. Herein, the "One-for-All" strategy is applied to synthesize both positive and negative electrodes of a hybrid SC (HSC) from a single pillared MOF. Specifically, Ni-DMOF-TM ([Ni(TMBDC)(DABCO)_0.5 ], TMBDC: 2,3,5,6-tetramethyl-1,4-benzenedicarboxylic acid, DABCO: 1,4-diazabicyclo[2.2.2]-octane) nanorods are directly grown on carbon fiber paper (CFP) (denoted as CFP@TM-nanorods) with the help of triethylamine and function as the positive electrode of HSC under alkaline electrolyte. Meanwhile, calcinated N-doped hierarchical porous carbon nanorods (CFP@TM-NPCs) are produced and utilized as the negative counter-electrode from a one-step heat treatment of CFP@TM-nanorods. After assembling these two electrodes together to make a hybrid device, the TM-nanorods//TM-NPCs exhibit a wide voltage window of 1.5 V with a high sloping discharge plateau between 1-1.2 V, indicating its great potential for practical applications. This as-described "One-for-All" strategy is widely applicable and highly reproducible in producing MOF-based electrode materials for HSC applications, which shortens the gap between experimental synthesis and practical application of MOFs in fast energy storage.

A 2D Conductive Organic-Inorganic Hybrid with Extraordinary Volumetric Capacitance at Minimal Swelling

Rational design and synthesis of 2D organic-inorganic hybrid materials is important for transformative technological advances for energy storage. Here, a 2D conductive hybrid lamella and its intercalation properties for thin-film supercapacitors are reported. The 2D organic-inorganic hybrid lamella comprises periodically stacked 2D nanosheets with 11.81 Å basal spacing, and is electronically conductive (605 S m^-1 ). In contrast to the pre-existing organic-based 2D materials, this material has extremely low gas-permeable porosity (16.5 m² g^-1 ) in contrast to the high ionic accessibility. All these structural features collectively contribute to the high capacitances up to 732 F cm^-3 , combined with small structural swelling at as low as 4.8% and good stability. At a discharge time of 6 s, the thin-film intercalation electrode delivers an energy density of 24 mWh cm^-3 , which universally outperforms the surface-dominant capacitive processes in porous carbons.

Construction of Bimetallic ZIF-Derived Co-Ni LDHs on the Surfaces of GO or CNTs with a Recyclable Method: Toward Reduced Toxicity of Gaseous Thermal Decomposition Products of Unsaturated Polyester Resin

This work proposed an idea of recycling in preparing Co-Ni layered double hydroxide (LDH)-derived flame retardants. A novel and feasible method was developed to synthesize CO-Ni LDH-decorated graphene oxide (GO) and carbon nanotubes (CNTs), by sacrificing bimetal zeolitic imidazolate frameworks (ZIFs). Organic ligands that departed from ZIFs were recyclable and can be reused to synthesize ZIFs. ZIFs, as transitional objects, in situ synthesized on the surfaces of GO or CNTs directly suppressed the re-stacking of the carbides and facilitated the preparation of GO@LDHs and CNTs@LDHs. As-prepared hybrids catalytically reduced toxic CO yield during the thermal decomposition of unsaturated polyester resin (UPR). What is more, the release behaviors of aromatic compounds were also suppressed during the pyrolysis process of UPR composites. The addition of GO@LDHs and CNTs@LDHs obviously inhibited the heat release and smoke emission behaviors of the UPR matrix during combustion. Mechanical properties of the UPR matrix also improved by inclusion of the carbides derivatives. This work paved a feasible method to prepare well-dispersed carbides@Co-Ni LDH nanocomposites with a more environmentally friendly method.

cRGD functionalised nanocarriers for targeted delivery of bioactives

The integrins α_vβ₃ play a very imperative role in angiogenesis and are overexpressed in endothelial cells of the tumour. Recent years have witnessed huge exploration in the field of α_vβ₃ integrin-mediated bioactive targeting for treatment of cancer. In these studies, the cRGD peptide has been employed extensively owing to their binding capacity to the α_vβ₃ integrin. Principally, RGD-based approaches comprise of antagonist molecules of the RGD sequence, drug-RGD conjugates, and most importantly tethering of the nanocarrier surface with the RGD peptide as targeting ligand. Targeting tumour vasculature or cells via cRGD conjugated nanocarriers have emerged as a promising technique for delivering chemotherapeutic drugs and imaging agents for cancer theranostics. In this review, primary emphasis has been given on the application of cRGD-anchored nanocarriers for targeted delivery of drugs, imaging agents, etc. for tumour therapy.

Bottom-up Formation of Carbon-Based Structures with Multilevel Hierarchy from MOF-Guest Polyhedra

Three-dimensional carbon-based structures have proven useful for tailoring material properties in structural mechanical and energy storage applications. One approach to obtain them has been by carbonization of selected metal-organic frameworks (MOFs) with catalytic metals, but this is not applicable to most common MOF structures. Here, we present a strategy to transform common MOFs, by guest inclusions and high-temperature MOF-guest interactions, into complex carbon-based, diatom-like, hierarchical structures (named for the morphological similarities with the naturally existing diatomaceous species). As an example, we introduce metal salt guests into HKUST-1-type MOFs to generate a family of carbon-based nano-diatoms with two to four levels of structural hierarchy. We report control of the morphology by simple changes in the chemistry of the MOF and guest, with implications for the formation mechanisms. We demonstrate that one of these structures has unique advantages as a fast-charging lithium-ion battery anode. The tunability of composition should enable further studies of reaction mechanisms and result in the growth of a myriad of unprecedented carbon-based structures from the enormous variety of currently available MOF-guest candidates.

Performance-Enhanced Activated Carbon Electrodes for Supercapacitors Combining Both Graphene-Modified Current Collectors and Graphene Conductive Additive

Graphene has been widely used in the active material, conductive agent, binder or current collector for supercapacitors, due to its large specific surface area, high conductivity, and electron mobility. However, works simultaneously employing graphene as conductive agent and current collector were rarely reported. Here, we report improved activated carbon (AC) electrodes (AC@G@NiF/G) simultaneously combining chemical vapor deposition (CVD) graphene-modified nickel foams (NiF/Gs) current collectors and high quality few-layer graphene conductive additive instead of carbon black (CB). The synergistic effect of NiF/Gs and graphene additive makes the performances of AC@G@NiF/G electrodes superior to those of electrodes with CB or with nickel foam current collectors. The performances of AC@G@NiF/G electrodes show that for the few-layer graphene addition exists an optimum value around 5 wt %, rather than a larger addition of graphene, works out better. A symmetric supercapacitor assembled by AC@G@NiF/G electrodes exhibits excellent cycling stability. We attribute improved performances to graphene-enhanced conductivity of electrode materials and NiF/Gs with 3D graphene conductive network and lower oxidation, largely improving the electrical contact between active materials and current collectors.

Morphological control of lanthanide ferrocyanides and their highly efficient catalytic degradation performance toward organic dyes under dark ambient conditions

KCe[FeII(CN)6]·4H2O (CePBA), a Prussian blue analogue, was successfully synthesized with various morphologies and different sizes. CePBA, when used as a heterogeneous catalyst, can rapidly and completely degrade a large number of methylene blue molecules in 30 seconds: 14.5 mg of MB (for each 5 mg of catalyst). The CePBA catalyst is reusable. These are very important parameters for practical applications.

Thermal Instability Induced Oriented 2D Pores for Enhanced Sodium Storage

Hierarchical porous structures are highly desired for various applications. However, it is still challenging to obtain such materials with tunable architectures. Here, this paper reports hierarchical nanomaterials with oriented 2D pores by taking advantages of thermally instable bonds in vanadium-based metal-organic frameworks (MOFs). High-temperature calcination of these MOFs accompanied by the loss of coordinated water molecules and other components enables the formation of orderly slit-like 2D pores in vanadium oxide/porous carbon nanorods (VO_x /PCs). This unique combination leads to an increase of the reactive surface area. In addition, optimized VO_x /PCs demonstrate high-rate capability and ultralong cycling life for sodium storage. The assembled full cells also show high capacity and cycling stability. This report provides an effective strategy for producing MOFs-derived composites with hierarchical porous architectures for energy storage.

Highly Porous Metal-Free Graphitic Carbon Derived from Metal-Organic Framework for Profiling of N-Linked Glycans

In this work, a highly efficient profiling of N-linked glycans was achieved by a facile and eco-friendly synthesized highly porous metal-free carbon material. The metal-free carbon was derived from a well-defined nanorod zinc metal-organic framework via the metal removal under a high-temperature carbonization, which exhibited a highly specific surface area of 1700 m²/g. After further oxidation, the oxidized metal-free carbon was applied to the selective isolation of N-linked glycans from complex biological samples due to the strong interaction between carbon and glycan as well as the size-exclusion mechanism. Twenty six N-linked glycans could be identified from the digest of a standard glycoprotein ovalbumin at a concentration of 0.01 μg/μL, and the detection limit of glycans could be down to 1 ng/μL with 21 N-linked glycans identified. When the mass ratio of the interfering protein bovine serum albumin vs a standard ovalbumin digest is up to 500:1, there were 24 N-glycans confidentially identified. From a real complex sample of a healthy human serum, there were 43 N-linked glycans identified after the enrichment of oxidized metal-free carbon. In a word, the metal-free carbon is opening up new prospect for the high-throughput identification of glycan.

Self-Template-Directed Metal-Organic Frameworks Network and the Derived Honeycomb-Like Carbon Flakes via Confinement Pyrolysis

Metal-organic frameworks (MOFs) have become a research hotspot since they have been explored as convenient precursors for preparing various multifunctional nanomaterials. However, the preparation of MOF networks with controllable flake morphology in large scale is not realized yet. Herein, a self-template strategy is developed to prepare MOF networks. In this work, layered double-metal hydroxide (LDH) and other layered metal hydroxides are used not only as a scaffold but also as a self-sacrificed metal source. After capturing the abundant metal cations identically from the LDH by the organic linkers, MOF networks are in situ formed. It is interesting that the MOF network-derived carbon materials retain the flake morphology and exhibit a unique honeycomb-like macroporous structure due to the confined shrinkage of the polyhedral facets. The overall properties of the carbon networks are adjustable according to the tailored metal compositions in LDH and the derived MOFs, which are desirable for target-oriented applications as exemplified by the electrochemical application in supercapacitors.

Ultrathin Hierarchical Porous Carbon Nanosheets for High-Performance Supercapacitors and Redox Electrolyte Energy Storage

The design of advanced high-energy-density supercapacitors requires the design of unique materials that combine hierarchical nanoporous structures with high surface area to facilitate ion transport and excellent electrolyte permeability. Here, shape-controlled 2D nanoporous carbon sheets (NPSs) with graphitic wall structure through the pyrolysis of metal-organic frameworks (MOFs) are developed. As a proof-of-concept application, the obtained NPSs are used as the electrode material for a supercapacitor. The carbon-sheet-based symmetric cell shows an ultrahigh Brunauer-Emmett-Teller (BET)-area-normalized capacitance of 21.4 µF cm^-2 (233 F g^-1 ), exceeding other carbon-based supercapacitors. The addition of potassium iodide as redox-active species in a sulfuric acid (supporting electrolyte) leads to the ground-breaking enhancement in the energy density up to 90 Wh kg^-1 , which is higher than commercial aqueous rechargeable batteries, maintaining its superior power density. Thus, the new material provides a double profits strategy such as battery-level energy and capacitor-level power density.

Mesoporous-silica induced doped carbon nanotube growth from metal-organic frameworks

Carbon materials, with a controllable structure, derived from metal-organic frameworks (MOFs) have emerged as a new class of electrocatalysts in renewable energy devices. However, efficient conversion of MOFs to small diameter doped carbon nanotubes in inert gases at high temperatures (>600 °C) remains a significant challenge. In this study, we first report the growth of small diameter cobalt and nitrogen co-doped carbon nanotubes (Co/N-CNTs) from mesoporous silica (mSiO2)-coated Co-based MOFs (ZIF-67). The presence of a layer of mSiO2 outside the ZIF-67 nanocrystals prevents the Co nanocatalysts from quick aggregation, and significantly serves as a unique 'sieve' for inducing the catalytic growth of CNTs during pyrolysis. The obtained Co/N-CNTs, with ∼13 nm diameter evolved from the pristine MOF architecture, exhibit higher catalytic activity and stability for oxygen reduction than commercial Pt/C electrocatalysts in alkaline media. This novel strategy opens a new avenue for the synthesis of Co/N-CNTs with great promise for developing high performance and cheap electrocatalysts.

In6S7 nanoparticle-embedded and sulfur and nitrogen co-doped microporous carbons derived from In(tdc)2 metal-organic framework

Indium sulfide nanoparticle (NP)-embedded microporous carbons co-doped with S- and N-dopants are easily prepared by a direct carbonization of the as-prepared In(iii)-based metal-organic framework (In-MOF), [Et₂NH₂][In(tdc)₂]·DEF, containing ditopic S-containing 2,5-thiophenedicarboxylate (tdc^2-) bridging linkers as a potential source of S-dopant. The charge on the anionic framework of [In(tdc)₂]^- is balanced by Et₂NH₂⁺, which is also a potential N-dopant. Simultaneous embedding of In-based NPs, S-, and N-co-doping is achieved in a simple single step carbonization of In-MOF. Three porous carbon materials (PCMs), PCM-700, PCM-800, and PCM-900, are obtained from the carbonization of In-MOF at 700, 800, and 900 °C, respectively. The gas sorption analysis indicates them as good CO₂ sorbents. The photocatalytic degradation of methyl orange by PCMs under visible light irradiation is also effectively operable owing to the photocatalytically active semiconducting indium sulfide NP with a small bandgap. The main component of indium sulfide NPs is revealed as In₆S₇ based on the powder X-ray diffraction pattern. Small amounts of metallic In and In₂S₃ are also observed. The specific capacitances of PCMs are also estimated from the galvanostatic charge/discharge curves. PCM-900 exhibits the highest gravimetric specific capacitance of 99.0 F g^-1 at a current density of 0.05 A g^-1.

Hybrid micro-/nano-structures derived from metal-organic frameworks: preparation and applications in energy storage and conversion

Metal-organic frameworks (MOFs), an important class of inorganic-organic hybrid crystals with intrinsic porous structures, can be used as versatile precursors or sacrificial templates for preparation of numerous functional nanomaterials for various applications. Recent developments of MOF-derived hybrid micro-/nano-structures, constructed by more than two components with varied functionalities, have revealed their extensive capabilities to overcome the weaknesses of the individual counterparts and thus give enhanced performance for energy storage and conversion. In this tutorial review, we summarize the recent advances in MOF-derived hybrid micro-/nano-structures. The synthetic strategies for preparing MOF-derived hybrid micro-/nano-structures are first introduced. Focusing on energy storage and conversion, we then discuss their potential applications in lithium-ion batteries, lithium-sulfur batteries, supercapacitors, lithium-oxygen batteries and fuel cells. Finally, we give our personal insights into the challenges and opportunities for the future research of MOF-derived hybrid micro-/nano-structures.

Coupling multiphase-Fe and hierarchical N-doped graphitic carbon as trifunctional electrocatalysts by supramolecular preorganization of precursors

A hydrogen bond-driven supramolecular strategy to synthesize multiphase-Fe anchoring on hierarchical N-doped graphitic carbon was proposed. As a result, the as-obtained catalysts showed unusual trifunctional activities in the oxygen reduction reaction, oxygen evolution reaction and hydrogen evolution reaction, even surpassing noble-metal catalysts such as Pt/C and RuO₂.