Boron‐Functionalized Graphene Oxide‐Organic Frameworks for Highly Efficient CO2 Capture

The capture and storage of CO₂ have been suggested as an effective strategy to reduce the global emissions of greenhouse gases. Hence, in recent years, many studies have been carried out to develop highly efficient materials for capturing CO₂. Until today, different types of porous materials, such as zeolites, porous carbons, N/B‐doped porous carbons or metal‐organic frameworks (MOFs), have been studied for CO₂ capture. Herein, the CO₂ capture performance of new hybrid materials, graphene‐organic frameworks (GOFs) is described. The GOFs were synthesized under mild conditions through a solvothermal process using graphene oxide (GO) as a starting material and benzene 1,4‐diboronic acid as an organic linker. Interestingly, the obtained GOF shows a high surface area (506 m² g⁻¹) which is around 11 times higher than that of GO (46 m² g⁻¹), indicating that the organic modification on the GO surface is an effective way of preparing a porous structure using GO. Our synthetic approach is quite simple, facile, and fast, compared with many other approaches reported previously. The synthesized GOF exhibits a very large CO₂ capacity of 4.95 mmol g⁻¹ at 298 K (1 bar), which is higher those of other porous materials or carbon‐based materials, along with an excellent CO₂/N₂ selectivity of 48.8.     

Isostructural NiII Metal–Organic Frameworks (MOFs) for Efficient Electrocatalysis of Oxygen Evolution Reaction and for Gas Sorption Properties

Design and synthesis of stable, active and cost-effective electrocatalyst for water splitting applications is an emerging area of research, given the depletion of fossil fuels. Herein, two isostructural Ni^II redox-active metal–organic frameworks (MOFs) containing flexible tripodal trispyridyl ligand ( L ) and linear dicarboxylates such as terephthalate (TA) and 2-aminoterphthalate (H₂NTA) are studied for their catalytic activity in oxygen evaluation reaction (OER). The 2D-layered MOFs form 3D hydrogen bonded frameworks containing one-dimensional hydrophilic channels that are filled with water molecules. The electrochemical studies reveal that MOFs display an efficient catalytic activity towards oxygen evolution reaction in alkaline conditions with an overpotential as low as 356 mV. Further, these 2D-MOFs exhibit excellent ability to adsorb water vapor (180–230 cc g⁻¹ at 273 K) and CO₂ (33 cc g⁻¹ at 273 K). The presence of hydrophilic functionality in the frameworks was found to significantly enhance the electrocatalytic activity as well as H₂O sorption.     

Highly Dispersible Hexagonal Carbon–MoS2–Carbon Nanoplates with Hollow Sandwich Structures for Supercapacitors

MoS₂, a typical layered transition-metal dichalcogenide, is promising as an electrode material in supercapacitors. However, its low electrical conductivity could lead to limited capacitance if applied in electrochemical devices. Herein, a new nanostructure composed of hollow carbon–MoS₂–carbon was successfully synthesized through an l -cysteine-assisted hydrothermal method by using gibbsite as a template and polydopamine as a carbon precursor. After calcination and etching of the gibbsite template, uniform hollow platelets, which were made of a sandwich-like assembly of partial graphitic carbon and two-dimensional layered MoS₂ flakes, were obtained. The platelets showed excellent dispersibility and stability in water, and good electrical conductivity due to carbon provided by the calcination of polydopamine coatings. The hollow nanoplate morphology of the material provided a high specific surface area of 543 m² g⁻¹, a total pore volume of 0.677 cm³ g⁻¹, and fairly small mesopores (≈5.3 nm). The material was applied in a symmetric supercapacitor and exhibited a specific capacitance of 248 F g⁻¹ (0.12 F cm⁻²) at a constant current density of 0.1 A g⁻¹; thus suggesting that hollow carbon–MoS₂–carbon nanoplates are promising candidate materials for supercapacitors.     

Ionic electro-active polymer actuator based on cobalt-containing nitrogen-doped carbon/conducting polymer soft electrode

Nanoscale cobalt-containing nitrogen-doped porous carbon (CoNC) materials were prepared by thermolysis of a zeolitic imidazolate framework (ZIF), ZIF-67, at different temperatures and their application for ionic electro-active polymer (EAP) actuator was evaluated. CoNC-700, which was obtained from ZIF-67 pyrolysis at 700 °C, exhibits specific surface area of 753.86 m² g⁻¹, pore volume of 0.5768 cm³ g⁻¹, and specific capacitance of 120.7 F∙g⁻¹. CoNC/conducting polymer soft electrode were fabricated by unitizing effective interaction of CoNC with poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS). High-performance ionic actuators were developed for the first time using this CoNC/PEDOT:PSS soft electrode. The developed ionic EAP actuator exhibited large peak-to-peak displacement of 20.4 mm and high bending strain of 0.28% (3 V and 0.1 Hz). Therefore, ZIFs or metal organic frameworks (MOFs) can be applied to provide significant improvements in EAP actuators, which can play key roles as technological advances toward bioinspired actuating devices required for next-generation soft and wearable electronics.     

Tuning of Microenvironment in Covalent Organic Framework via Fluorination Strategy promotes Selective CO2 Capture

Herein, we have designed and synthesized two heteroatom (N, O) rich covalent organic frameworks (COF), PD-COF and TF-COF , respectively, to demonstrate their relative effect on CO₂ adsorption capacity and also CO₂/N₂ selectivity. Compared to the non-fluorinated PD-COF (BET surface area 805 m² g⁻¹, total pore volume 0.3647 ccg⁻¹), a decrease in BET surface area and also pore volume have been observed for fluorinated TF-COF due to the incorporation of fluorine to the porous framework (BET surface area 451 m² g⁻¹, total pore volume 0.2978 ccg⁻¹). This fact leads to an enormous decrease in the CO₂ adsorption capacity and CO₂/N₂ selectivity of TF-COF , though it shows stronger affinity towards CO₂ with a Qst of 37.76 KJ/mol. The more CO₂ adsorption capacity by PD-COF can be attributed to the large specific surface area with considerable amount of micropore volume compared to the TF-COF . Further, PD-COF exhibited CO₂/N₂ selectivity of 16.8, higher than that of TF-COF (CO₂/N₂ selectivity 13.4).     

Coordination-Modulated Metal Tetrathiafulvalene Octacarboxylate Frameworks for High-Performance Lithium-Ion Battery Anodes

Modulation of the ligands and coordination environment of metal–organic frameworks (MOFs) has been an effective and relatively unexplored avenue for improving the anode performance of lithium-ion batteries (LIBs). In this study, three MOFs are synthesized, namely, M₄(o-TTFOB)(bpm)₂(H₂O)₂ (where M is Mn, Zn, and Cd; o-H₈TTFOB is ortho-tetrathiafulvalene octabenzoate; and bpm is 2,2′-bipyrimidine), based on a new ligand o-H₈TTFOB with two adjacent carboxylates on one phenyl, which allows us to establish the impact of metal coordination on the performance of these MOFs as anode materials in LIBs. Mn-o-TTFOB and Zn-o-TTFOB, with two more uncoordinated oxygen atoms from o-TTFOB⁸⁻, show higher reversible specific capacities of 1249 mAh g⁻¹ and 1288 mAh g⁻¹ under 200 mA g⁻¹ after full activation. In contrast, Cd-o-TTFOB shows a reversible capacity of 448 mAh g⁻¹ under the same condition due to the lack of uncoordinated oxygen atoms. Crystal structure analysis, cyclic voltammetry measurements of the half-cell configurations, and density functional theory calculations have been performed to explain the lithium storage mechanism, diffusion kinetics, and structure-function relationship. This study demonstrates the advantages of MOFs with high designability in the fabrication of LIBs.     

A Carbocationic Triarylmethane-Based Porous Covalent Organic Network

A thermally stable carbocationic covalent organic network (CON), named RIO-70 was prepared from pararosaniline hydrochloride, an inexpensive dye, and triformylphloroglucinol in solvothermal conditions. This nanoporous organic material has shown a specific surface area of 990 m² g⁻¹ and pore size of 10.3 Å. The material has CO₂ uptake of 2.14 mmol g⁻¹ (0.5 bar), 2.7 mmol g⁻¹ (1 bar), and 6.8 mmol g⁻¹ (20 bar), the latter corresponding to 3 CO₂ molecules adsorbed per pore per sheet. It is shown to be a semiconductor, with electrical conductivity (σ) of 3.17×10⁻⁷ S cm⁻¹, which increases to 5.26×10⁻⁴ S cm⁻¹ upon exposure to I₂ vapor. DFT calculations using periodic conditions support the findings.     

Synthesis of Co3O4/Carbon Heteroaerogels with Ultrahigh Capacitance via Polyethyleneimine Intercalation of Co2BIM4 Nanosheets

The development of metal–organic frameworks (MOFs)-based supercapacitors have attracted intense concentration in recent years due to their regularly arranged porous and tunable pore sizes. However, the performance of the MOFs-derived supercapacitors is also low because of their poor electrical conductivity and rarely accessible active sites. In the present work, we developed a Co-MOF (namely Co₂BIM₄, BIM=benzimidazole) nanosheets derived Co₃O₄/nitrogen-doped carbon (Co₂BIM₄-Co₃O₄/NC) heteroaerogel as a novel supercapacitor electrode. The 3D Co₂BIM₄-Co₃O₄/NC heteroaerogels were obtained by directly intercalating polyethyleneimine (PEI) into the interlayers of Co₂BIM₄ nanosheets and following by carbonizing the resulting Co₂BIM₄/PEI composite. The Co₂BIM₄-Co₃O₄/NC electrode possessed 3D conductive framework with an overlapped hetero-interface and expanded interlayers, leading to fast and stable charge transfer/diffusion and an enhanced pseudocapacitance performance. Therefore, the Co₂BIM₄-Co₃O₄/NC electrode showed ultrahigh capacitance of 2568 F g⁻¹ at 1 A g⁻¹, 1747 F g⁻¹ at 10 A g⁻¹, and excellent long cycling time with a capacitance preservation of 92.7 % following 10000 cycles at 10 A g⁻¹, which is very promising for applications in supercapacitors and other energy storage devices.     

Sulfone-Modified Covalent Organic Frameworks Enabling Efficient Photocatalytic Hydrogen Peroxide Generation via One-Step Two-Electron O2 Reduction

Photocatalytic oxygen reduction reaction (ORR) offers a promising hydrogen peroxide (H₂O₂) synthetic strategy, especially the one-step two-electron (2e⁻) ORR route holds great potential in achieving highly efficient and selectivity. However, efficient one-step 2e⁻ ORR is rarely harvested and the underlying mechanism for regulating the ORR pathways remains greatly obscure. Here, by loading sulfone units into covalent organic frameworks (FS-COFs), we present an efficient photocatalyst for H₂O₂ generation via one-step 2e⁻ ORR from pure water and air. Under visible light irradiation, FS-COFs exert a superb H₂O₂ yield of 3904.2 μmol h⁻¹ g⁻¹, outperforming most reported metal-free catalysts under similar conditions. Experimental and theoretical investigation reveals that the sulfone units accelerate the separation of photoinduced electron-hole (e⁻-h⁺) pairs, enhance the protonation of COFs, and promote O₂ adsorption in the Yeager-type, which jointly alters the reaction process from two-step 2e⁻ ORR to the one-step one, thereby achieving efficient H₂O₂ generation with high selectivity.     

A Two-Dimensional Metal–Organic Polymer Enabled by Robust Nickel–Nitrogen and Hydrogen Bonds for Exceptional Sodium-Ion Storage

Organic electrode materials suffer from low electronic conductivity and poor structure stability. Herein, a metal–organic polymer, Ni-coordinated tetramino-benzoquinone (Ni-TABQ), is synthesized via d–π hybridization. The polymer chains are stitched by hydrogen bonds to feature as a robust two-dimensional (2D) layered structure. It offers both electron conduction and Na⁺ diffusion pathways along the directions of the polymer chains and the hydrogen bonds. With both the conjugated benzoid carbonyls and imines as the redox centers for the insertion and extraction of Na⁺, the Ni-TABQ delivers high capacities of about 469.5 mAh g⁻¹ at 100 mA g⁻¹ and 345.4 mAh g⁻¹ at 8 A g⁻¹. The large capacities are sustained for 100 cycles with almost 100 % coulombic efficiencies. The exceptional electrochemical performance is attributed to the unique 2D electron conduction and Na⁺ diffusion pathways enabled by the robust Ni–N and hydrogen bonds.     

A Novel Aluminum-Based Metal-Organic Framework with Uniform Micropores for Trace BTEX Adsorption

Metal-organic frameworks (MOFs) are potential porous adsorbents for benzene, toluene, ethylbenzene and xylene (BTEX). A novel MOF, using low toxic aluminum (Al) as the metal, named as ZJU-620(Al), with uniform micropore size of 8.37±0.73 Å and specific surface area of 1347 m² g⁻¹, was synthesized. It is constructed by one-dimensional rod-shaped AlO₆ clusters, formate ligands and 4,4′,4′′-(2,4,6-trimethylbenzene-1,3,5-triyl) tribenzoic ligands. ZJU-620(Al) exhibits excellent chemical-thermal stability and adsorption for trace BTEX, e.g., benzene adsorption of 3.80 mmol g⁻¹ at P/P₀=0.01 and 298 K, which is the largest one reported. Using Grand Canonical Monte Carlo simulations and Single-crystal X-ray diffraction analyses, it was observed that the excellent adsorption could be attributed to the high affinity of BTEX molecules in ZJU-620(Al) micropores because the kinetic diameters of BTEX are close up to the pore size of ZJU-620(Al).     

A Three-Dimensional Porous Organic Semiconductor Based on Fully sp2-Hybridized Graphitic Polymer

Dimensionality plays an important role in the charge transport properties of organic semiconductors. Although three-dimensional semiconductors, such as Si, are common in inorganic materials, imparting electrical conductivity to covalent three-dimensional organic polymers is challenging. Now, the synthesis of a three-dimensional π-conjugated porous organic polymer (3D p-POP) using catalyst-free Diels–Alder cycloaddition polymerization followed by acid-promoted aromatization is presented. With a surface area of 801 m² g⁻¹, full conjugation throughout the carbon backbone, and an electrical conductivity of 6(2)×10⁻⁴ S cm⁻¹ upon treatment with I₂ vapor, the 3D p-POP is the first member of a new class of permanently porous 3D organic semiconductors.     

A Facile Grinding Method for the Synthesis of 3D Ag Metal–Organic Frameworks (MOFs) Containing Ag6Mo7O24 for High-Performance Supercapacitors

Successful synthesis of three kinds of dynamically stable compounds by a simple grinding method is reported, giving Ag₆Mo₇O₂₄, Ag-BTC (Ag-MOF, BTC=benzene-1,3,5-tricarboxylic acid), and {Ag₆Mo₇O₂₄}@Ag-MOF metal–organic frameworks (MOFs). According to the electrochemical dynamic analysis, these materials have pseudocapacitor behavior and high capacitance. The unique nanorod structure of {Ag₆Mo₇O₂₄}@Ag-MOF provides more active sites, faster ion/electron transfer, and electrolyte diffusion pathways, resulting in excellent specific capacitance (971 F g⁻¹) higher than the other compounds. {Ag₆Mo₇O₂₄}@Ag-MOF (glassy carbon electrode) also has an excellent rate ability (60.1 %) and long cycle stability (98 % retention after 5000 cycles). In addition, the fully symmetrical button battery (with nickel foam as the current collector) fabricated with {Ag₆Mo₇O₂₄}@Ag-MOF delivers an energy density of 11.1 Wh kg⁻¹ at 600.1 Wh kg⁻¹ coupled with excellent cycling stability (86.4 %) at 1.2 V. These results demonstrate a new simple grinding method to prepare polyoxometalate-based metal–organic frameworks (POMOFs) for high-performance materials.     

Preparation of Hierarchical Porous Activated Carbon from Banana Leaves for High-performance Supercapacitor: Effect of Type of Electrolytes on Performance

We demonstrate a facile efficient way to fabricate activated carbon nanosheets (ACNSs) consisting of hierarchical porous carbon materials. Simply heating banana leaves with K₂CO₃ produce ACNSs having a unique combination of macro-, meso- and micropores with a high specific surface area of ∼1459 m² g⁻¹. The effects of different electrolytes on the electrochemical supercapacitor performance and stability of the ACNSs are tested using a two-electrode system. The specific capacitance (C_sp) values are 55, 114, and 190 F g⁻¹ in aqueous 0.5 M sodium sulfate, organic 1 M tetraethylammonium tetrafluoroborate in acetonitrile, and pure ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF₆]) electrolytes, respectively. The ACNSs also shows the largest potential window of 3.0 V, the highest specific energy (59 Wh kg⁻¹) and specific power (750 W kg⁻¹) in [BMIM][PF₆]. A mini-prototype device is prepared to demonstrate the practicality of the ACNSs.     

A Dual-Ligand Porous Coordination Polymer Chemiresistor with Modulated Conductivity and Porosity

Single-ligand-based electronically conductive porous coordination polymers/metal–organic frameworks (EC-PCPs/MOFs) fail to meet the requirements of numerous electronic applications owing to their limited tunability in terms of both conductivity and topology. In this study, a new 2D π-conjugated EC-MOF containing copper units with mixed trigonal ligands was developed: Cu₃(HHTP)(THQ) (HHTP=2,3,6,7,10,11-hexahydrotriphenylene, THQ=tetrahydroxy-1,4-quinone). The modulated conductivity (σ≈2.53×10⁻⁵ S cm⁻¹ with an activation energy of 0.30 eV) and high porosity (ca. 441.2 m² g⁻¹) of the Cu₃(HHTP)(THQ) semiconductive nanowires provided an appropriate resistance baseline and highly accessible areas for the development of an excellent chemiresistive gas sensor.     

Large-Scale Synthesis of MOF-Derived Superporous Carbon Aerogels with Extraordinary Adsorption Capacity for Organic Solvents

Carbon aerogels (CAs) with 3D interconnected networks hold promise for application in areas such as pollutant treatment, energy storage, and electrocatalysis. In spite of this, it remains challenging to synthesize high-performance CAs on a large scale in a simple and sustainable manner. We report an eco-friendly method for the scalable synthesis of ultralight and superporous CAs by using cheap and widely available agarose (AG) biomass as the carbon precursor. Zeolitic imidazolate framework-8 (ZIF-8) with high porosity is introduced into the AG aerogels to increase the specific surface area and enable heteroatom doping. After pyrolysis under inert atmosphere, the ZIF-8/AG-derived nitrogen-doped CAs show a highly interconnected porous mazelike structure with a low density of 24 mg cm⁻³, a high specific surface area of 516 m² g⁻¹, and a large pore volume of 0.58 cm⁻³ g⁻¹. The resulting CAs exhibit significant potential for application in the adsorption of organic pollutants.     

Regulating Oxygen Configuration in Hierarchically Porous Carbon Nanosheets for High-Rate and Durable Na+ Storage

Surface oxygen functionalities (particularly C−O configuration) in carbon materials have negative influence on their electrical conductivity and Na⁺ storage performance. Herein, we propose a concept from surface chemistry to regulate the oxygen configuration in hierarchically porous carbon nanosheets (HPCNS). It is demonstrated that the C−O/C=O ratio in HPCNS reduces from 1.49 to 0.43 and its graphitization degree increases by increasing the carbonization temperature under a reduction atmosphere. Remarkably, such high graphitization degree and low C−O content of the HPCNS-800 are favorable for promoting its electron/ion transfer kinetics, thus endowing it with high-rate (323.6 mAh g⁻¹ at 0.05 A g⁻¹ and 138.5 mAh g⁻¹ at 20.0 A g⁻¹) and durable (96 % capacity retention over 5700 cycles at 10.0 A g⁻¹) Na⁺ storage performance. This work permits the optimization of heteroatom configurations in carbon for superior Na⁺ storage.     

Cooperative Proton and Li-ion Conduction in a 2D-Layered MOF via Mechanical Insertion of Lithium Halides

Ionic conduction in highly designable and porous metal–organic frameworks has been explored through the introduction of various ionic species (H⁺, OH⁻, Li⁺, etc.) using post-synthetic modification such as acid, salt, or ionic liquid incorporation. Here, we report on high ionic conductivity (σ>10⁻² S cm⁻¹) in a two-dimensionally (2D)-layered Ti-dobdc (Ti₂(Hdobdc)₂(H₂dobdc), H₄dobdc: 2,5-dihydroxyterephthalic acid) via LiX (X=Cl, Br, I) intercalation using mechanical mixing. The anionic species in lithium halide strongly affect the ionic conductivity and durability of conductivity. Solid-state pulsed-field gradient nuclear magnetic resonance (PFG NMR ) verified the high mobility of H⁺ and Li⁺ ions in the temperature range of 300–400 K. In particular, the insertion of Li salts improved the H⁺ mobility above 373 K owing to strong binding with H₂O. Furthermore, the continuous increase in Li⁺ mobility with temperature contributed to the retention of the overall high ionic conductivity at high temperatures.     

Phenazine-based Compound Realizing Separate Hydrogen and Oxygen Production in Electrolytic Water Splitting

Electrocatalytic water splitting powered by renewable energy is a sustainable approach for hydrogen production. However, conventional water electrolysis may suffer from gas mixing, and the different kinetics between hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) will limit the direct use of unstable renewable energies, leading to increased cost of H₂ production. Herein, a novel phenazine-based compound is synthesized to develop the solid-state redox mediator associated water splititng process, and thus decoupling the H₂ and O₂ production in acid solution without the use of membrane. Excitingly, this organic redox mediator exhibits high specific capacity (290 mAh g⁻¹ at 0.5 A g⁻¹), excellent rate performance (186 mAh g⁻¹ at 30 A g⁻¹) and long cycle life (3000 cycles) due to its π-conjugated aromatic structure and the fast kinetics of H⁺ storage/release process. Furthermore, a membrane-free decoupled water electrolysis architecture driven by solar energy is achieved, demonstrating high-purity H₂ production at different times.     

β-MnO2/Metal–Organic Framework Derived Nanoporous ZnMn2O4 Nanorods as Lithium-Ion Battery Anodes with Superior Lithium-Storage Performance

Nanoporous ZnMn₂O₄ nanorods have been successfully synthesized by calcining β-MnO₂/ZIF-8 precursors (ZIF-8 is a type of metal–organic framework). If measured as an anode material for lithium-ion batteries, the ZnMn₂O₄ nanorods exhibit an initial discharge capacity of 1792 mA h g⁻¹ at 200 mA g⁻¹, and an excellent reversible capacity of 1399.8 mA h g⁻¹ after 150 cycles (78.1 % retention of the initial discharge capacity). Even at 1000 mA g⁻¹, the reversible capacity is still as high as 998.7 mA h g⁻¹ after 300 cycles. The remarkable lithium-storage performance is attributed to the one-dimensional nanoporous structure. The nanoporous architecture not only allows more lithium ions to be stored, which provides additional interfacial lithium-storage capacity, but also buffers the volume changes, to a certain degree, during the Li⁺ insertion/extraction process. The results demonstrate that nanoporous ZnMn₂O₄ nanorods with superior lithium-storage performance have the potential to be candidates for commercial anode materials in lithium-ion batteries.