Metal-Organic Framework-Derived Nanoporous Metal Oxides toward Supercapacitor Applications: Progress and Prospects

Dual-Purpose 3D Pillared Metal-Organic Framework with Excellent Properties for Catalysis of Oxidative Desulfurization and Energy Storage in Asymmetric Supercapacitor

This study proposes an approach for improving catalysis of oxidative desulfurization (ODS) of diesel fuel under mild reaction conditions and enhancing supercapacitor (SC) properties for storage of a high amount of charge. Our approach takes advantage of a novel dual-purpose cobalt(II)-based metal-organic framework (MOF), [Co(2-ATA)₂(4-bpdb)₄] _n (2-ATA: 2-aminoterephthalic acid and 4-bpdb: N, N-bis-pyridin-4-ylmethylene-hydrazine as the pillar spacer), which is called NH₂-TMU-53. Due to the stability of the used compound, we decided to evaluate the capability of this compound as a novel electrode material for storing energy in supercapacitors, and also to investigate its catalytic capabilities. It is demonstrated that the addition of H₂O₂ as an oxidant enhances the efficiency of sulfur removal, which indicates that NH₂-TMU-53 can efficiently catalyze the ODS reaction. According to the kinetics results, the catalyzed process follows pseudo-first-order kinetics and exhibits 15.57 kJ mol^-1 activation energy. Moreover, with respect to the radical scavenging evaluations, the process is governed by direct catalytic oxidation rather than indirect oxidative attack of radicals. Furthermore, NH₂-TMU-53 was applied as an electrode material for energy storage in SCs. This material is used in the three-electrode system and shows a specific capacitance of 325 F g^-1 at 5 A g^-1 current density. The asymmetric supercapacitor of NH₂-TMU-53//activated carbon evaluates the further electrochemical activity in real applications, delivers the high power density (2.31 kW kg^-1), high energy density (50.30 Wh kg^-1), and long cycle life after 6000 cycles (90.7%). Also, the asymmetric supercapacitor practical application was demonstrated by a glowing red light-emitting diode and driving a mini-rotating motor. These results demonstrate that the fabricated device presents a good capacity for energy storage without pyrolyzing the MOF structures. These findings can guide the development of high-performance SCs toward a new direction to improve their practical applications and motivate application of MOFs without pyrolysis or calcination.

In situ encapsulation of Co3O4 polyhedra in graphene sheets for high-capacitance supercapacitors

Co3O4 polyhedra were well encapsulated in reduced graphene oxide (rGO) sheets by in situ growth of Co-based zeolitic imidazolate framework (ZIF-67) polyhedra in the presence of graphene oxide followed by thermal annealing. The resultant rGO/Co3O4 composites consist of a continuously-conductive double-network constructed from graphene sheets and the derived N-doped carbons from ZIF-67, showing a large specific surface area of 523 m2 g-1. The as-fabricated symmetrical supercapacitor based on rGO/Co3O4 exhibits a high specific capacitance of 277.5 F g-1 at 25 A g-1 and an energy density of 24.7 W h kg-1 at a power density of up to 40 kW kg-1. The supercapacitor also retains 87.5% of the initial capacitance over 5000 cycles at 5 A g-1. Such large capacitance, high energy density, and excellent cycling stability for rGO/Co3O4 are attributable to the 3D double conductive network from 2D graphene sheets and porous channels of pseudo-capacitive Co3O4 polyhedra.

Toward fiber-, paper-, and foam-based flexible solid-state supercapacitors: electrode materials and device designs

Flexible solid-state supercapacitors possess promising safety performance and intrinsic fast charging-discharging properties, enabling them to accomplish the requirements of lightweight and multifunctional wearable electronics that have recently become fairly popular. Because electrode materials are the core component of flexible solid-state supercapacitors, we exhaustively review the recent investigations involving electrode materials that have used carbons, metal oxides, and conductive polymers. The principles and methods of optimizing and fabricating electrodes for use in flexible supercapacitors are discussed through a comprehensive analysis of the literature. In addition, we focused on three types of flexible solid-state supercapacitors (fiber-, paper-, and porous foam-based structures) to satisfy the requirements of flexible electronic devices. Further, we summarize the practical applications of flexible solid-state supercapacitors, including energy conversion/collection devices and energy storage/detection devices. Finally, we provide the developmental direction for flexible solid-state supercapacitors in the future.

From fluorene molecules to ultrathin carbon nanonets with an enhanced charge transfer capability for supercapacitors

It is a big challenge to synthesize ultrathin carbon nanonets with an enhanced charge transfer capability for high-performance energy storage devices. Herein, ultrathin carbon nanonets (UCNs) were successfully synthesized for the first time from fluorene, a typical aromatic molecule, by a template strategy for supercapacitors. The formation mechanism of UCNs was determined using Density Functional Theory and Materials Studio, in which the fluorene-derived radicals were assembled into UCNs in the template-confinement space with the assistance of KOH. The as-made UCNs feature interconnected high-conductivity net-like architectures with enhanced charge transfer capability, evidenced by their high capacitance, excellent rate performance and cycling stability for symmetrical supercapacitors in a KOH electrolyte. This finding may provide a significant step forward in understanding the formation mechanism of graphene-like materials from more complicated aromatic hydrocarbon molecules, and our work may draw wide attention in the fields of aromatic chemistry and carbon-based energy storage materials.

Metal-Organic Frameworks and Their Derived Materials: Emerging Catalysts for a Sulfate Radicals-Based Advanced Oxidation Process in Water Purification

With the ever-growing environmental issues, sulfate radical (SO₄^•- )-based advanced oxidation processes (SR-AOPs) have been attracting widespread attention due to their high selectivity and oxidative potential in water purification. Among various methods generating SO₄^•- , employing heterogeneous catalysts for activation of peroxymonosulfate or persulfate has been demonstrated as an effective strategy. Therefore, the future advances of SR-AOPs depend on the development of adequate catalysts with high activity and stability. Metal-organic frameworks (MOFs) with large surface area, ultrahigh porosity, and diversity of material design have been extensively used in heterogeneous catalysts, and more recently, enormous effort has been made to utilize MOFs-based materials for SR-AOPs applications. In this work, the state-of-the-art research on pristine MOFs, MOFs composites, and their derivatives, such as oxides, metal/carbon hybrids, and carbon materials for SR-AOPs, is summarized. The mechanisms, including radical and nonradical pathways, are also detailed in the discussion. This work will hopefully promote the future development of MOFs-based materials toward SR-AOPs applications.

Well-Defined Cu2 O/Cu3 (BTC)2 Sponge Architecture as Efficient Phenolics Scavenger: Synchronous Etching and Reduction of MOFs in confined-pH NH3 ⋅H2 O

Fabrication of low-dimensional nano-MOFs as well as nanoparticles/metal-organic frameworks (MOFs) hybrids has sparked new scientific interests but remains a challenging task. Taking Cu₃ (BTC)₂ as a proof of concept, it is demonstrated thats NH₃ ⋅H₂ O solution of a confined pH value can readily shape the bulk Cu₃ (BTC)₂ into nanoscale Cu₃ (BTC)₂ , beyond the need to control the crystal growth kinetics of MOFs. Adjusting the pH of NH₃ ⋅H₂ O within a much small range (10-11) allows fine tuning over the size and shape of nanoscale Cu₃ (BTC)₂ . Particularly at pH = 11, NH₃ ⋅H₂ O exhibits weak reducibility that triggers a reduction of part of Cu₃ (BTC)₂ into Cu₂ O, while shaping the other into Cu₃ (BTC)₂ nanowires. Benefiting from the coincidence of reduction and etching effects, the newly generated Cu₂ O dots can in situ anchor onto adjacent Cu₃ (BTC)₂ nanowires at highly dispersive state, forming a well-defined sponge-like architecture built of Cu₂ O dots and nano-Cu₃ (BTC)₂ . The CuO_x derived from annealing of the Cu₂ O dots/nano-Cu₃ (BTC)₂ hybrid preserves the sophisticated sponge architecture and high porosity, and exhibits promising applications in phenol scavenging, with efficiency outperforming its counterparts and many other Cu-based catalysts reported in literature. It is anticipated that the findings here pave the way for the rational design of intricate nano-MOFs in a more efficient way.

SnS2 /SnO2 Heterostructures towards Enhanced Electrochemical Performance of Lithium-Sulfur Batteries

Lithium-sulfur (Li-S) batteries have been recognized as outstanding candidates for energy storage systems due to their superiority in terms of energy density. To meet the requirements for practical use, it is necessary to develop an effective method to realize Li-S batteries with high sulfur utilization and cycle stability. Here, a strategy to construct heterostructure composites as cathodes for high performance Li-S batteries is presented. Taking the SnS₂ /SnO₂ couple as an example, SnS₂ /SnO₂ nanosheet heterostructures on carbon nanofibers (CNFs), named C@SnS₂ /SnO₂ , were designed and synthesized. Considering the electrochemical performance of SnS₂ /SnO₂ heterostructures, it is interesting to note that the existence of heterointerfaces could efficiently improve lithium ion diffusion rate so as to accelerate the redox reaction significantly, thus leading to the enhanced sulfur utilization and more excellent rate performance. Benefiting from the unique structure and heterointerfaces of C@SnS₂ /SnO₂ materials, the battery exhibited excellent cyclic stability and high sulfur utilization. This work may provide a powerful strategy for guiding the design of sulfur hosts from selecting the material composition to constructing of microstructure.

Hollow Functional Materials Derived from Metal-Organic Frameworks: Synthetic Strategies, Conversion Mechanisms, and Electrochemical Applications

Hollow materials derived from metal-organic frameworks (MOFs), by virtue of their controllable configuration, composition, porosity, and specific surface area, have shown fascinating physicochemical properties and widespread applications, especially in electrochemical energy storage and conversion. Here, the recent advances in the controllable synthesis are discussed, mainly focusing on the conversion mechanisms from MOFs to hollow-structured materials. The synthetic strategies of MOF-derived hollow-structured materials are broadly sorted into two categories: the controllable synthesis of hollow MOFs and subsequent pyrolysis into functional materials, and the controllable conversion of solid MOFs with predesigned composition and morphology into hollow structures. Based on the formation processes of hollow MOFs and the conversion processes of solid MOFs, the synthetic strategies are further conceptually grouped into six categories: template-mediated assembly, stepped dissolution-regrowth, selective chemical etching, interfacial ion exchange, heterogeneous contraction, and self-catalytic pyrolysis. By analyzing and discussing 14 types of reaction processes in detail, a systematic mechanism of conversion from MOFs to hollow-structured materials is exhibited. Afterward, the applications of these hollow structures as electrode materials for lithium-ion batteries, hybrid supercapacitors, and electrocatalysis are presented. Finally, an outlook on the emergent challenges and future developments in terms of their controllable fabrications and electrochemical applications is further discussed.

Formation of nickel-cobalt sulphide@graphene composites with enhanced electrochemical capacitive properties

Here, nickel-cobalt sulphide particles embedded in graphene layers (porous Ni-Co-S@G), were successfully prepared by one-step annealing of metallocene/metal-organic framework (MOF) hybrids involving simultaneous carbonization and sulfidation. Benefiting from the porous structure, highly conductive graphene layers and large loading of super-capacitive Ni-Co-S, the obtained Ni-Co-S@G composites exhibited excellent electrochemical performance with a specific capacitance of 1463 F g-1 at a current density of 1 A g-1. A flexible solid-state asymmetric supercapacitor (ASC), assembled with Ni-Co-S@G and active carbon, demonstrated a high energy density of 51.0 W h kg-1 at a power density of 650.3 W kg-1. It is noteworthy that the ASC offered robust flexibility and excellent performance that was maintained when the devices were bent at various angles. The results indicate that the as-prepared materials could potentially be applied in high-performance electrochemical capacitors.

Temperature-Dependent Morphologies of Precursors: Metal-Organic Framework-Derived Porous Carbon for High-Performance Electrochemical Double-Layer Capacitors

In this work, three Cu metal-organic framework samples with tunable rhombic, squama, and trucated bipyramid morphologies have been synthesized at 0, 25, and 60 °C, respectively, and further employed as precursors to initially prepare Cu@C composites by the calcination-thermolysis procedure. Then Cu@C composites have been etched with HCl and subsequently activated with KOH to obtain activated porous carbon (APC-0, -25, and -60). Interestingly, APC-25 presents a loose multilevel morphology of cabbage and possesses the largest specific surface area (1880.4 m² g^-1) and pore volume (0.81 cm³ g^-1) among these APC materials. Consequently, APC-25 also exhibits the highest specific capacitance of 196 F g^-1 at 0.5 A g^-1, and the corresponding symmetric supercapacitor cell (SSC) achieves a remarkable energy density of 11.8 Wh kg^-1 at a power density of 350 W kg^-1. Furthermore, APC-25 shows excellent cycling stability, and the loss of capacitance is only 7.7% even after 10000 cycles at 1 A g^-1. Significantly, five light-emitting diodes can be lit by six SSCs, which proves that APC-25 can be used in energy storage devices.

Rapid synthesis of Ni(OH)2/graphene nanosheets and NiO@Ni(OH)2/graphene nanosheets for supercapacitor applications

β-Ni(OH)₂ or NiO@Ni(OH)₂ grew on commercial graphene nanosheets with high specific capacitance and excellent rate capability.

Anchoring carbon layers and oxygen vacancies endow WO3−x/C electrode with high specific capacity and rate performance for supercapacitors

Herein, novel hierarchical carbon layer-anchored WO_3−x/C ultra-long nanowires were developed via a facile solvent-thermal treatment and a subsequent rapid carbonization process. The inner anchored carbon layers and abundant oxygen vacancies endowed the WO_3−x/C nanowire electrode with high conductivity, as measured with a single nanowire, which greatly enhanced the redox reaction active sites and rate performance. Surprisingly, the WO_3−x/C electrode exhibited outstanding specific capacitance of 1032.16 F g⁻¹ at the current density of 1 A g⁻¹ in a 2 M H₂SO₄ electrolyte and maintained the specific capacitance of 660 F g⁻¹ when the current density increased to 50 A g⁻¹. Significantly, the constructed WO_3−x/C//WO_3−x/C symmetric supercapacitors achieved specific capacitance of 243.84 F g⁻¹ at the current density of 0.5 A g⁻¹ and maintained the capacitance retention of 94.29% after 5000 charging/discharging cycles at the current density of 4 A g⁻¹. These excellent electrochemical performances resulted from the fascinating structure of the WO_3−x/C nanowires, showing a great potential for future energy storage applications.

A high-performance supercapacitor electrode comprising hierarchical carbon layer-anchored WO_3−x/C nanowires with inner abundant redox reaction active sites and numerous oxygen vacancies is presented.

One-pot synthesis of ZnS nanowires/Cu7S4 nanoparticles/reduced graphene oxide nanocomposites for supercapacitor and photocatalysis applications

ZnS nanowires/Cu₇S₄ nanoparticles/rGO nanocomposites were fabricated as photocatalysts and supercapacitor electrodes for the first time.

ZIF-67 derived Co3O4/carbon aerogel composite for supercapacitor electrodes

We report carbon aerogels with a 3D hierarchical porous structure as a backbone to support nanoporous Co₃O₄ derived from ZIF-67 for supercapacitors.

Rosette-like MoS2 nanoflowers as highly active and stable electrodes for hydrogen evolution reactions and supercapacitors

MoS₂ is regarded as one of the cost-effective materials for many important applications. In this work, we report a simple one-step hydrothermal method for the directed synthesis of a rosette-like MoS₂ nanoflower modified electrode without using adhesion agents. Interestingly, owing to the hierarchical structures, the as-prepared MoS₂-based electrode exhibits significantly enhanced performance for both the hydrogen evolution reaction in acidic environments and supercapacitors. When used in the hydrogen evolution reaction, the electrode shows a low overpotential of ∼0.25 V at 10 mA cm⁻², a Tafel slope of ∼71.2 mV per decade, and long-term durability over 20 h of hydrogen evolution reaction operation at 10 mV cm⁻². In addition, as a supercapacitor electrode, it exhibits a good capacity of 137 mF cm⁻² at a current density of 10 mA cm⁻² and excellent stability in 1 M H₂SO₄ at a scan rate of 50 mV s⁻¹. The outstanding performances of the as-prepared materials may be ascribed to the unique 3D architectures of the rosette-like MoS₂ nanoflowers. This work could provide a strategy to explore low-cost and highly efficient electrocatalysts with desired nanostructures for the hydrogen evolution reaction and supercapacitors applications.

A simple strategy to synthesize interlayer spacing-enlarged rosette-like MoS₂ nanoflowers for both the hydrogen evolution reaction and supercapacitive energy storage.

Design of a Zn-MOF biosensor via a ligand “lock” for the recognition and distinction of S-containing amino acids

A new method of introducing a ‘lock’ ligand into the frame of MOFs is described to achieve the first example of a MOF-based biosensor for the recognition and distinction of S-containing amino acids.

Zeolitic imidazolate framework-derived Co3S4@Co(OH)2 nanoarrays as self-supported electrodes for asymmetric supercapacitors

Core–shell Co₃S₄@Co(OH)₂ nanosheet arrays with enhanced electrochemical capacitive performance were designed using a ZIF-engaged strategy.

A cobalt metal–organic framework (Co-MOF): a bi-functional electro active material for the oxygen evolution and reduction reaction

Co-MOF catalyzes the ORR efficiently with a lower onset potential (0.85 V vs. RHE) by a four electron reduction path with better durability. It needs only 280 mV overpotential to deliver the state-of-art current density of 10 mA cm⁻².

Construction of a hollow porous carbon spheres@CoP/nitrogen-doped carbon supported platinum catalyst for high performance methanol oxidation

A Pt–HPCS@CoP/NC catalyst with excellent catalytic activity, CO-tolerance and durability was synthesized for the methanol oxidation reaction.

A phosphatized NiCo LDH 1D dendritic electrode for high energy asymmetric supercapacitors

1D dendritic 4M-P@NiCo LDHs were synthesized by phosphatized Ni/Co hydroxide and exhibited high areal capacitance of 7 F cm⁻² at 50 mA cm⁻². Asymmetric supercapacitor obtained 18.1 Wh Kg⁻¹ energy density and 77.17% (5000 cycles) capacity retention.

Core–shell assembly of Co3O4@NiO-ZnO nanoarrays as battery-type electrodes for high-performance supercapatteries

Core–shell Co₃O₄@NiO-ZnO nanoarrays are fabricated by annealing metal–organic framework assisted precursors and investigated as battery-type electrode for supercapattery.

A MnCo2 O4 @NiMoO4 Core-Shell Composite Supported on Nickel Foam as a Supercapacitor Electrode for Energy Storage

A MnCo₂ O₄ @NiMoO₄ composite was synthesized on nickel foam by a two-step method. The composite has a core-shell structure in which MnCo₂ O₄ nanoneedles are wrapped by NiMoO₄ nanoflakes. The MnCo₂ O₄ @NiMoO₄ /Ni foam is applied as a binder-free electrode for supercapacitors and it achieves a specific capacitance of up to 1718 F g^-1 at a current density of 1 A g^-1 , and 84 % capacitance retention after 6000 charge-discharge cycles. The capacitance of the MnCo₂ O₄ @NiMoO₄ composite is much higher than MnCo₂ O₄ nanoneedles and NiMoO₄ nanoflakes alone. Moreover, a hybrid supercapacitor is assembled by applying the MnCo₂ O₄ @NiMoO₄ /Ni foam as the positive electrode, activated carbon/Ni foam as the negative electrode. The hybrid supercapacitor reaches an energy density of up to 42.3 W h kg^-1 at a power density of 797 W kg^-1 , a power density of 6256 W kg^-1 at an energy density of 17.4 W h kg^-1 , and 86 % capacitance retention after 2000 charge-discharge cycles. The results suggest that the rational design of electrode materials with such structure and composition is an effective strategy to improve electrochemical performance.

Metal-Organic Framework-Assisted Construction of TiO2/Co3O4 Highly Ordered Necklace-like Heterostructures for Enhanced Ethanol Vapor Sensing Performance

In this work, we report a metal-organic framework (MOF)-assisted strategy to synthesize necklace-like TiO₂/Co₃O₄ nanofibers with highly ordered heterostructures via a facile approach including electrospinning and subsequent calcination. Polycrystalline TiO₂ nanofibers and Co₃O₄ nanocages are consummately interconnected to form a highly ordered heterogeneous nanostructure, which can be of benefit for precisely accommodating the interface resistance of the p-n heterojunctions and the future realization of improved material performance. The ethanol-gas-sensing investigation showed that TiO₂/Co₃O₄ nanofiber sensors exhibited a strong ethanol response ( R_air/ R_gas -1 = 16.7 @ 150 ppm) and a low operating temperature of 150 °C. The sensing enhancement mechanism of the TiO₂/Co₃O₄ nanofibers is related to the formation of heterojunctions at interfaces and the high catalytic activity of MOF-derived Co₃O₄. Furthermore, this versatile method is a promising approach to constructing ordered heterostructures and extending the MOF-based heterogeneous materials toward wide applications.

ZD2-Engineered Gold Nanostar@Metal-Organic Framework Nanoprobes for T1 -Weighted Magnetic Resonance Imaging and Photothermal Therapy Specifically Toward Triple-Negative Breast Cancer

Compared with other subtypes of breast cancer, triple-negative breast cancer (TNBC) is seriously threatening to human life. Therefore, it is a matter of urgency to develop multifunctional nanoprobes for visualized theranostics of TNBC, achieving specific targeting toward only TNBC, but not other subtypes. Nanoscale metal-organic frameworks (MOFs) show important potential in visualized theranostics of tumors, but it is critical to synthesize well-defined core-shell MOF-based nanocomposites by encapsulating a single nanoparticle within MOF. In this study, a TNBC-targeted peptide (ZD2)-engineered, and a single gold nanostar (AuNS) coated within MIL-101-NH₂ (Fe) by coating MOF with four cycles, obtain well-defined core-shell AuNS@MOF-ZD2 nanocomposites, which are expected to achieve T₁ -weighted magnetic resonance imaging and photothermal therapy (PTT) specifically targeting toward TNBC. The prepared AuNS@MOF-ZD2 nanocomposites possess good biocompatibility, efficient T₁ -weighted magnetic resonance (MR) relaxivity and stable photothermal conversion ability with an efficiency of 40.5%. The in vitro and in vivo characterizations prove their performances of T₁ -weighted MR and PTT with a low power density of 808 nm laser, achieving excellent theranostic efficacy in TNBC. Importantly, it is demonstrated that the prepared AuNS@MOF-ZD2 nanoprobes can specifically target TNBC cells (MDA-MB-231), but not other subtypes of breast cancer cells (MDA-MB-435, MDA-MB-468, and MCF-7), indicating their promising application in visualized theranostics of breast cancers with molecular classification.

A Flexible Supercapacitor with High True Performance

The demand for better “true performance” of supercapacitors, which is defined as the energy density based on the packaged cell with high active mass loading, is spurred by the ever-increasing energy storage market. The true performance of present supercapacitors is unsatisfactory, greatly limited by the currently used current collectors. Here, we develop a through-pore structured nickel current collector with excellent flexibility by electrodepositing nickel on laser-drilled stainless steel sheets filled with epoxy resin. Based on the new current collector, the electrodes possess higher performance than those fabricated by employing conventional current collectors. At a high active mass loading, the assembled supercapacitors show superior flexibility and high energy densities of 50.4 W hr L⁻¹ and 30.1 W hr kg⁻¹, respectively, based on the packaged cell, outperforming the present supercapacitors. Our strategy provides a new opportunity for promoting the further development of supercapacitors by enhancing the true performance.

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A free-standing through-pore structured nickel film (TPNF) has been developed

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The TPNF is employed as the current collector for supercapacitors

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A packaged supercapacitor with high active mass loading is fabricated

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The packaged supercapacitor shows excellent flexibility and high true performance

Engineering hydrogenated manganese dioxide nanostructures for high-performance supercapacitors

Improving the rate capability of transition metal oxides is of great important for the development of high-performance electrodes for supercapacitors. Here, a novel strategy of hydrogenation to enhance the electron transfer rate of manganese dioxide (MnO₂) is proposed. Detailed preparative parameters (i.e. hydrogenation temperature and time) are systematically investigated. The hydrogenated MnO₂ (H-MnO_x) exhibits modified crystal phase/surface structures and increased electrical conductivity. The prepared H-MnO_x exhibits high specific capacitance (640 mF cm^-2 at current density of 1 mA cm^-2), good rate capability (89.6% of capacitance retained from 1 to 10 mA cm^-2), and good cycling stability (84.6% retention after 1000 cycles). The high specific capacitance is ascribed to the unique interconnected ultrathin nanosheets structure, which could not only provide porous channels for electrolyte infiltration to offer sufficient electrode/electrolyte interface, but also shorten the ions diffusion distance inside the active material. The good rate capability could be attributed to the good conductivity of the H-MnO_x nanosheets, which was confirmed by the DFT calculation. These results highlight the importance of hydrogenation as a facile yet effective strategy to improve the rate capability of transition metal oxides for supercapacitors.

Rational Design of Mimic Multienzyme Systems in Hierarchically Porous Biomimetic Metal-Organic Frameworks

A facile approach was reported to establish mimic multienzyme systems with hierarchically porous (HP) biomimetic metal-organic frameworks (MOFs) and natural enzymes for tandem catalysis. The hierarchically porous MOF HP-PCN-224(Fe) with peroxidase-like activity and tunable hierarchical porosity was synthesized via a modulator-induced strategy. HP-PCN-224(Fe) not only acts as the enzyme-immobilization matrix but also as an effective enzyme mimic, which could cooperate with the immobilized natural enzyme to catalyze the cascade reactions. The mimic multienzyme systems were used for the efficient colorimetric detection of a series of biomolecules, including glucose and uric acid. This work displays the great potential to construct highly functional biocatalysts by integrating the merits of both natural enzymes and MOF mimics, which are promising for applications in biosensing and biomimetic catalysis.