Ultrathin hierarchical porous carbon nanosheets for high-performance supercapacitors and redox electrolyte energy storage

ICN2 is funding from the CERCA Programme/Generalitat de CatalunyaThe 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 (233 F g), 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, 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 densit

Graphene-based metal-organic framework hybrids for applications in catalysis, environmental, and energy technologies

Current energy and environmental challenges demand the development and design of multifunctional porous materials with tunable properties for catalysis, water purification, and energy conversion and storage. Because of their amenability to de novo reticular chemistry, metal-organic frameworks (MOFs) have become key materials in this area. However, their usefulness is often limited by low chemical stability, conductivity and inappropriate pore sizes. Conductive two-dimensional (2D) materials with robust structural skeletons and/or functionalized surfaces can form stabilizing interactions with MOF components, enabling the fabrication of MOF nanocomposites with tunable pore characteristics. Graphene and its functional derivatives are the largest class of 2D materials and possess remarkable compositional versatility, structural diversity, and controllable surface chemistry. Here, we critically review current knowledge concerning the growth, structure, and properties of graphene derivatives, MOFs, and their graphene@MOF composites as well as the associated structure- property-performance relationships. Synthetic strategies for preparing graphene@MOF composites and tuning their properties are also comprehensively reviewed together with their applications in gas storage/separation, water purification, catalysis (organo-, electro-, and photocatalysis), and electrochemical energy storage and conversion. Current challenges in the development of graphene@MOF hybrids and their practical applications are addressed, revealing areas for future investigation. We hope that this review will inspire further exploration of new graphene@MOF hybrids for energy, electronic, biomedical, and photocatalysis applications as well as studies on previously unreported properties of known hybrids to reveal potential "diamonds in the rough".Web of Science12224173381724

Self-assembly of tetrabromoterephthalic acid with different metal system: diversity in dimensionalities, structures and gas adsorption

A new series of coordination compounds of different dimensionalities, {Cd<SUB>2</SUB>(TBTH)<SUB>2</SUB>(TBT)(DMF)<SUB>6</SUB>} (1), {Cu(TBT)(DMF)<SUB>2</SUB>}<SUB>n</SUB> (2), {Ni(TBT)(DMF)<SUB>2</SUB>(EtOH)<SUB>2</SUB>}<SUB>n</SUB> (3) and {Mn(TBT)(DMF)}<SUB>n</SUB> (4) have been synthesized under similar reaction conditions and stoichiometry using tetrabromoterephthalic acid (TBTH<SUB>2</SUB>) as a building block. Single crystal X-ray diffraction study reveals 1 is a dimeric discrete complex whereas 2 and 3 are found to be 1D coordination polymers and all the three compounds extend to three dimensions by non-covalent (H-bonding and O⋯Br) interactions. Compound 4 has a 3D framework structure where {Mn(CO<SUB>2</SUB>)}<SUB>n</SUB> chains are cross-linked by TBT linkers and DMF molecule also acts as a bidentate bridging ligand. The difference in dimensionalities can be correlated to the metal ions (Cd<SUP>II</SUP>, Cu<SUP>II</SUP>, Ni<SUP>II</SUP> and Mn<SUP>II</SUP>) having different ionic radius. Compound 4 does not contain any guest solvent molecule but removal of bridging DMF molecules creates a 1D channel with dimension of 2.1 × 4.2 &#x000C5;2. Adsorption studies reveal that the desolvated compound 4 (4′) with unsaturated MnII sites can uptake an appreciable amount of CO<SUB>2</SUB> at 195 K (15 wt.%), and H<SUB>2</SUB> at 77 K (∼0.4 wt.%) although surface area is not significant

Stabilization of Cu<SUB>2</SUB>O nanoparticles on a 2D metal–organic framework for catalytic Huisgen 1,3-dipolar cycloaddition reaction

We report a simple methodology for the stabilization of Cu2O nanoparticles of size 2–4 nm on the polar pore surface of a 2D metal–organic framework, {[Zn(Himdc)(bipy)0.5]·DMF} (1). For the first time, a Cu2O@1a (1a: desolvated 1) composite has been utilized as a recyclable catalyst for the Huisgen 1,3-dipolar cycloaddition reaction of terminal alkynes and aliphatic/aromatic azides for the synthesis of 1,2,3-triazoles

Temperature induced structural transformations and gas adsorption in the Zeolitic Imidazolate Framework ZIF-8: A Raman study

Here we have used Raman spectroscopy to investigate molecular level changes in the Zeolitic Imidazolate Framework ZIF-8 (a prototypical zeolite-like porous metal organic framework) as a function of temperature. Temperature dependent Raman spectra suggest that at low temperature the softening of the C–H stretching frequencies is due to the decrease in steric hindrance between the methyl groups of methyl imidazole. The larger separation between the methyl groups opens the window for increased nitrogen and methane uptake at temperatures below 153 K. The appearance of Raman bands at 2323 cm^–1 and 2904 cm^–1 at or below 153 K in ZIF-8 are characteristic signatures of the adsorbed nitrogen and methane gases respectively. Nanoscale ZIF-8 uptakes more molecules than bulk ZIF-8, and as a result we could provide evidence for encaged CO₂ at 203 K yielding its Raman mode at 1379 cm^–1

A bimodal anionic MOF: turn-off sensing of Cu<SUP>II</SUP> and specific sensitization of Eu<SUP>III</SUP>

A novel porous anionic MOF {[Mg<SUB>3</SUB>(ndc)<SUB>2.5</SUB>(HCO<SUB>2</SUB>)<SUB>2</SUB>(H<SUB>2</SUB>O)][NH<SUB>2</SUB>Me<SUB>2</SUB>]·2H<SUB>2</SUB>O·DMF} (1) having exchangeable dimethyl amine cations in 1D channels has been synthesized and characterized. Through cation exchange, 1 manifests bimodal functionality, being a turn-off sensor of Cu<SUP>II</SUP> on one hand, and a selective sensitizer of Eu<SUP>III</SUP> emitting intense pure red emission on the other

Metal-organic framework/conductive polymer hybrid materials for supercapacitors

This review article focuses on supercapacitor electrode materials based on composites of metal-organic frameworks (MOFs) and conductive polymers (CPs). MOFs have attracted enormous attention due to their unique properties such as high porosity, nanoscale periodicity, large surface area and structural diversity. The major disadvantage of MOFs for energy storage applications is their low electrical conductivity. Combining MOFs with other (nano)materials is an effective strategy to increase the specific capacitance and overall performance of electrode materials. CPs are attractive compounds because of their controllable conductivity and mechanical properties, particularly including large specific capacitance, ease of fabrication, high environmental stability and good film-forming properties. This review mostly deals with hybridization strategies and discusses critically various types of CPs with different MOFs in relation to hybridization techniques and obtained results. An excellent summary of MOF@CP hybrids is provided with respect to recent advances in this field and presents new perspectives for enhancing the electrochemical performance of future MOF@CP supercapacitors.Web of Science26art. no. 10138

Unveiling BiVO4 nanorods as a novel anode material for high performance lithium ion capacitors: beyond intercalation strategies

Energy storage is increasingly demanded in many new niches of applications from wearables to unmanned autonomous vehicles. However, current energy storage systems are unable to fulfill the power requirements (high energy at high power) needed for these novel applications. Recently, Li-ion capacitors (LICs) have been spotted as hybrid devices with the potential to display high energy and high power. Nevertheless, it is still a great challenge to achieve high performance LICs due to the unmatched kinetic properties and capacity between anode and cathode materials. Herein, we are presenting our first seminal report on the use of BiVO4 nanorods as a new anode material for LICs coupled with a partially reduced graphene oxide (PRGO) cathode. The BiVO4 nanorods show an excellent reversible capacity of 877 mA h g−1 (ultrahigh volumetric capacity of 4560 mA h cm−3) at 1.1 A g−1 with a great capacity retention (in half-cell design), which is the highest value reported so far for metal vanadates. Later on, a LIC was constructed with BiVO4 as the anode and PRGO as the cathode electrode, delivering a high energy density of 152 W h kg−1 and a maximum power density of 9.6 kW kg−1 compared to that for hard carbon and intercalation (such as Li4Ti5O12 and Li3VO4) based anode materials. Additionally, the BiVO4//PRGO LIC exhibits a good cyclability of 81% over 6000 cycles. Thus, this investigation opens up new opportunities to develop different LIC systems

Hybrid nanocomposites of ZIF-8 with graphene oxide exhibiting tunable morphology, significant CO<SUB>2</SUB> uptake and other novel properties

Hybrid nanocomposites of graphene oxide (GO) with ZIF-8 exhibit tunable nanoscale morphology and porosity, both determined by the GO content, coordination modulation being responsible for such properties. These materials also give rise to high CO2 storage capability and can be used as precursors to prepare GO@ZnS nanocomposites

Three-dimensional metal–organic framework with highly polar pore surface: H<SUB>2</SUB> and CO<SUB>2</SUB> storage characteristics

A three-dimensional (3D) pillared-layer metal–organic framework, [Cd(bipy)0.5(Himdc)](DMF)]n (1), (bipy =4,4′-bipyridine and Himdc = 4,5-imidazoledicarboxylate) has been synthesized and structurally characterized. The highly rigid and stable framework contains a 3D channel structure with highly polar pore surfaces decorated with pendant oxygen atoms of the Himdc linkers. The desolvated framework [Cd(bipy)0.5(Himdc)]n (1′) is found to exhibit permanent porosity with high H2 and CO2 storage capacities. Two H2 molecules occluded per unit formula of 1′ and the corresponding heat of H2 adsorption (&#x00394;HH2) is about ∼9.0 kJ/mol. The high value of &#x00394;HH2 stems from the preferential electrostatic interaction of H2 with the pendent oxygen atoms of Himdc and aromatic bipy linkers as determined from first-principles density functional theory (DFT) based calculations. Similarly, DFT studies indicate CO2 to preferentially interact electrostatically (C&#x003B4;+···O&#x003B4;-) with the uncoordinated pendent oxygen of Himdc. It also interacts with bipy through C–H···O bonding, thus rationalizing the high heat (&#x00394;HCO2 ∼ 35.4 kJ/mol) of CO2 uptake. Our work unveiled that better H2 or CO2 storage materials can be developed through the immobilization of reactive hetero atoms (O, N) at the pore surfaces in a metal–organic framework