Porous Framework Research Articles

Adsorption Properties of Hydrophobic Porous Coordination Polymers of Zinc-Oxalic Acid with Triazole and Amino Triazole Mixture Ligands

The porous coordination polymers were prepared from Zn2+ and oxalic acid with 2 linker ligands, 1,2,4-triazole (Taz) and 3-amino-1,2,4-triazole (ATaz). The adsorption of N2 after adsorption of degassed CO2 in the pore frameworks increased by 3 times. The flexibility of this structure is due to the interaction of CO2 molecules with the amine groups contained in it, thereby increasing its porosity.

3D framework MXene Ti3C2/g-C3N4/Fe3Si magneto-dielectric foam unveiling superior microwave absorption and thermal management performance

In conjunction with the swift advancement of detection technologies, the challenge persists in developing advanced stealth materials. The focus of this work is on the straightforward synthesis of a hybrid magneto-dielectric nanocomposite material composed of MXene Ti3C2/Fe3Si/g-C3N4 within a three-dimensional melamine foam framework, designed to deliver effective stealth capabilities. The high electrical conductivity and considerable permittivity of Ti3C2 have imposed limitations on its effectiveness in electromagnetic wave absorbers. In this context, the utilization of this compound in combination with substances like g-C3N4 and Fe3Si to fine-tune impedance matching and fully exploit the intrinsic properties is suggested. Furthermore, the distinctive 3D porous frameworks of the melamine foam, combined with the accordion-like structure of the MXene compound, extend and elongate paths for wave propagation to enhance energy dissipation. Through the activation of various loss mechanisms, it was possible to achieve a minimum reflection loss of −44.3 dB using a 1.5 mm thickness with an effective absorption bandwidth of 1.9 GHz. The enhancement of stealth performance was achieved through the combination of heterojunction interfaces among hybrid components and a 3D interconnected continuous path within the structure.

Carbonized porous zeolitic imidazolate framework as promising electrode for electrochemical supercapacitors

In order to manufacture effective supercapacitors with improved electrochemical performance, it is imperative to investigate greater surface area electrode materials. This work describes the development of a cost-effective method for the carbonization of porous zeolitic imidazole framework (ZIF8) to utilize as electrode of electrochemical supercapacitors. The electrode materials were prepared by synthesizing highly porous ZIF8-P followed by pyrolysis at 500 °C (ZIF8-P-500). The pyrolysis of ZIF-8 significantly strengthened the porous behavior by maintaining their hexagonal particles and obtaining high surface to volume ratio. The measurements using constant current charge/discharge (GCD) and cyclic voltammetry (CV) were used to evaluate the electrochemical capacitance characteristics of the synthesized ZIF8-P based electrode. The supercapacitor assembly using the optimized ZIF8-P electrode exhibited a high specific capacitance of ∼423.9 Fg–1 with exceptional cycle stability by maintaining capacitance of ∼86.7 % from its initial capacitance after 5000 cycles. Thus, the results indicate that the ZIF8-P based supercapacitor offers a compelling path for creating porous carbon electrodes from MOFs using low cost pyrolysis for advancing supercapacitor technology.

Supramolecular Polymer Frameworks with Controlled and Uniform Pore Apertures.

Porous frameworks with controlled pore structure and tunable aperture are greatly demanded. However, precise synthesis of this kind of materials is a formidable challenge. Herein, we report the fabrication of two-dimensional (2D) supramolecular polymer frameworks using a precisely synthesized rod-like helical polyisocyanide as link. Four three-arm star-shaped polyisocyanides with the degree of the polymerization of 10, 20, 30 and 40, and having 2-ureido-4[1H]-pyrimidinone (UPy) terminals were synthesized. 2D-Crystalline polymer frameworks with apertures of 5.3, 10.1, 13.9, and 19.1 nm were respectively obtained through intermolecular hydrogen bonding interaction between the terminal Upy units. The pore aperture is dependent on the length of polyisocyanide backbone. Thus, well-defined supramolecular polymer frameworks with controlled and uniform hexagonal pores were obtained, as proved by small-angle X-ray scattering (synchrotron radiation facility), atomic force microscopy, and Brunauer-Emmett-Teller analyses. The frameworks with uniform large pore aperture were used to purify nanomaterials and immobilize biomacromolecules. For instance, the membranes of the polymer frameworks could size-fractionation of silver nanoparticles into uniform nanoparticles with very low dispersity. The frameworks with large aperture facilitated the inclusion of myoglobin and enhanced the stability and catalytic activity.

Functional light diffusers based on hybrid CsPbBr3/SiO2 aero-framework structures for laser light illumination and conversion

The new generation of laser-based solid-state lighting (SSL) white light sources requires new material systems capable of withstanding, diffusing, and converting high intensity laser light. State-of-the-art systems use a blue light emitting diode or laser diode in combination with color conversion materials, such as yellow emitting Ce-doped phosphors or red and green emitting quantum dots (QD), to produce white light. However, for laser-based high-brightness illumination thermal management and uniform light diffusion are still major challenges in the quest to convert a highly focused laser beam into an efficient lighting solution. Here, we present a material system consisting of a highly open porous (> 99%) framework structure of hollow SiO2 microtubes. This framework structure enables efficient and uniform light distribution as well as ensuring good thermal management even at high laser powers of up to 5 W, while drastically reducing the speckle contrast. By further functionalizing the microtubes with halide perovskite QDs (SiO2@CsPbBr3 as model system) color conversion from UV to visible light is achieved. By depositing an ultrathin (~ 5.5 nm) film of poly(ethylene glycol dimethyl acrylate) (pEGDMA) via initiated chemical vapor deposition (iCVD), the luminescent stability of the QDs against moisture is enhanced. The demonstrated hybrid material system paves the way for the design of advanced and functional laser light diffusers and converters that can meet the challenges associated with laser-based SSL applications.Graphical

A π−π stacked porous framework for highly efficient second near-infrared photothermal effects and photo-thermo-electric conversion

Near-infrared (NIR) photothermal compounds, which convert low-energy NIR photons into heat, have recently attracted significant attention due to their potential applications in many areas such as photothermal imaging, diagnosis and therapy, photosensors, and catalysis. Photothermal conversion efficiency (PCE), a critical parameter of NIR photothermal materials, significantly influences their practical performance. However, exploring highly efficient NIR photothermal compounds, particularly in the NIR-II domain, remains a significant challenge. Herein, we report on a highly efficient NIR-II photothermal compound based on a novel π−π stacked porous framework {[Ni4Cl2(ONDI)2(bpy)4]⋅2Cl⋅2H2O⋅xDMF⋅yH2O}n (1). This compound features a porous supramolecular framework constructed through intermolecular π−π interactions. Additionally, compound 1 exhibits broad optical absorption spanning from the ultraviolet to the NIR region, with an edge extending to 1600 nm. Under irradiation with a 1064 nm laser, compound 1 demonstrates significant NIR-II photothermal effects, achieving a remarkable PCE of 84.4 %, attributed to the formation of charge states and the abundant π−π interactions in its crystal structure. When integrated with commercial thermoelectric generators, compound 1 shows promising potential for photo-thermo-electric conversion, with a maximum open-circuit voltage of 250 mV and 350 mV under irradiation of 1 sun and 2 suns, respectively. Furthermore, the output power density of 1@TEC1-12701 reaches 0.53 W/m2 under 1 sun and 1.23 W/m2 under 2 suns.

Recovering noble metals from waste streams using porous organic frameworks for heterogeneous catalysis

AbstractRecovering noble metals from waste resources and incorporating them into catalysts stands out as a promising strategy for advancing sustainability within the catalysis field. This review provides a comprehensive overview of recent investigations into noble metal recovery from waste streams, specifically employing porous organic frameworks (POFs). Additionally, the study delves into the utilization of the resultant composites, enriched with noble metals, in heterogeneous catalysis. Moreover, we offer insights into the challenges faced and outline prospects for the practical implementation of extracting noble metal catalysts from waste streams using POFs, aiming to develop cost-effective, sustainable, and efficient heterogeneous catalysts.

Analyzing Foam Injection Dynamics in Porous Media: A Combined Computational and Experimental Approach

The study of foam injection dynamics into porous media holds numerous applications, with its primary use being the optimization of the oil extraction process. Additionally, it finds utility in various other domains, including soil decontamination techniques. This study focuses on evaluating foam injection through low-cost experiments and computational models. The model integrates a classic two-phase immiscible fluid flow in a porous media framework, augmented by a mobility reduction factor to simulate foam’s impact on gas phase mobility. Simple experiments were conducted to assess water displacement using both gas and gas-foam injection methods. Results revealed that while gas injection tends to form preferential paths rapidly, leading to gas disruption, foam injection generates a more compact front, enhancing sweep efficiency by mitigating preferential path formation. The computational model successfully reproduced the experimental findings qualitatively. This research introduces a cost-effective experiment suitable for didactic purposes, illustrating complex concepts and underscoring the complementary nature of experimental and computational methodologies in advancing engineering techniques.

Integrating Multiple Redox‐Active Units into Conductive Covalent Organic Frameworks for High‐Performance Sodium‐Ion Batteries

The rational design of porous covalent organic frameworks (COFs) with high conductivity and reversible redox activity is the key to improving their performance in sodium‐ion batteries (SIBs). Herein, we report a series of COFs (FPDC‐TPA‐COF, FPDC‐TPB‐COF, and FPDC‐TPT‐COF) based on an organosulfur linker, (trioxocyclohexane‐triylidene)tris(dithiole‐diylylidene))hexabenzaldehyde (FPDC). These COFs feature two‐dimensional crystalline structures, high porosity, good conductivity, and densely packed redox‐active sites, making them suitable for energy storage devices. Among them, FPDC‐TPT‐COF demonstrates a remarkably high specific capacity of 420 mAh g−1 (0.2 A g−1), excellent cycling stability (~87% capacity retention after 3000 cycles, 1.0 A g−1) and high rate performance (339 mAh g−1 at 2.0 A g−1) as an anode for SIBs, surpassing most reported COF‐based electrodes. The superior performance is attributed to the dithiole moieties enhancing the conductivity and the presence of redox‐active carbonyl, imine, and triazine sites facilitating Na storage. Furthermore, the sodiation mechanism was elucidated through in‐situ experiments and density functional theory (DFT) calculations. This work highlights the advantages of integrating multiple functional groups into redox‐active COFs for the rational design of efficient and stable SIBs.

Integrating Multiple Redox-Active Units into Conductive Covalent Organic Frameworks for High-Performance Sodium-Ion Batteries.

The rational design of porous covalent organic frameworks (COFs) with high conductivity and reversible redox activity is the key to improving their performance in sodium-ion batteries (SIBs). Herein, we report a series of COFs (FPDC-TPA-COF, FPDC-TPB-COF, and FPDC-TPT-COF) based on an organosulfur linker, (trioxocyclohexane-triylidene)tris(dithiole-diylylidene))hexabenzaldehyde (FPDC). These COFs feature two-dimensional crystalline structures, high porosity, good conductivity, and densely packed redox-active sites, making them suitable for energy storage devices. Among them, FPDC-TPT-COF demonstrates a remarkably high specific capacity of 420 mAh g-1 (0.2 A g-1), excellent cycling stability (~87% capacity retention after 3000 cycles, 1.0 A g-1) and high rate performance (339 mAh g-1 at 2.0 A g-1) as an anode for SIBs, surpassing most reported COF-based electrodes. The superior performance is attributed to the dithiole moieties enhancing the conductivity and the presence of redox-active carbonyl, imine, and triazine sites facilitating Na storage. Furthermore, the sodiation mechanism was elucidated through in-situ experiments and density functional theory (DFT) calculations. This work highlights the advantages of integrating multiple functional groups into redox-active COFs for the rational design of efficient and stable SIBs.

Porous structural battery composite for coordinated integration of mechanical and electrical functionalities

AbstractStructural battery composites (SBCs) represent an emerging multifunctional technology in which materials functionalized with energy storage capabilities are used to build load‐bearing structural components. However, due to the liquid electrolyte contamination in structural battery electrolyte (SBE) and the large volume expansion of active battery materials, the poor interlayer interfacial in multilayer SBCs often causes difficulties in practical use. In this study, a new porous LiFePO4‐graphite SBC is designed and fabricated by independently distributing battery materials and resin matrix on carbon fiber fabric in pattern lattice form to prepare electrodes prepreg. The cured porous composite framework supports the load‐bearing function while limiting the electrochemical reaction in liquid electrolyte within lattices. The electrodes show reversible electric resistance after 3000 bending cycles with radius as small as 10 mm. The mechanical properties enhance significantly with tensile strength of 486.1 MPa and Young's modulus of 9.1 GPa compared to that with a liquid–solid biphasic mixed SBE structure. The SBC also exhibits a favorable capacity of 27.8 mAh/g at 0.1C. This straightforward integration path of mechanical and electrical functionalities is compatible with the manufacturing process of aerospace composite structures, which will provide an efficient and convenient energy supply solution for distributed electronics.Highlights A porous full‐cell structural battery composite (SBC) was designed and fabricated with prepregs. A suspension deposition and volatilization method was developed for robust battery material coating. Electrodes layer exhibited reversible electric resistance after 3000 tensile/bending cycles. The tensile strength and modulus increased significantly compared to the SBC with liquid–solid biphasic mixed structural battery electrolyte. Coordinated integration path was completely compatible with the manufacturing process of aerospace composite structures.

MOF-Derived Ni/NiO-C Nanocomposites as Bifunctional Electrocatalysts Capable of Driving Both ORR and OER.

Bifunctional electrocatalysts, capable of efficiently driving both the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER), are crucial for advancing electrochemical processes. While noble-metal-based catalysts are widely recognized for their role in oxygen processes, current state-of-the-art designs are limited to either ORR or OER activity, presenting a notable research gap. In addressing this challenge, we have developed a novel Ni/NiO-C nanocomposite catalyst derived from a nickel-based metal-organic framework (Ni-SKU-5). For the ORR, the Ni/NiO-C catalyst exhibits an onset potential of 0.95 V vs RHE in a 1.0 M KOH solution, coupled with a Tafel slope of -99 mV dec-1 at 1600 rpm. Moreover, the catalyst displays excellent stability, maintaining a performance of over 90% after 10 h of continuous reaction. Furthermore, the catalyst proves effective in the OER, boasting an overpotential of 370 mV (at 10 mA cm-2) and a Tafel slope of 114 mV dec-1, highlighting its bifunctionality. The bifunctional overpotential of the Ni/NiO-C composite is measured at 820 mV, surpassing that of the 20% Pt/C electrocatalyst (860 mV), highlighting its potential for practical applications. Comparative experiments establish the origin of the robust bifunctional reactivity toward the conformal hybrid structure, porous framework, and the synergistic effect operating among the constituents of the nanocomposite.

Asymmetric Cu−N1O3 Sites Coupling Atop‐type and Bridge‐type Adsorbed *C1 for Electrocatalytic CO2‐to‐C2 Conversion

Abstract2D functional porous frameworks offer a platform for studying the structure–activity relationships during electrocatalytic CO2 reduction reaction (CO2RR). Yet challenges still exist to breakthrough key limitations on site configuration (typical M−O4 or M−N4 units) and product selectivity (common CO2‐to‐CO conversion). Herein, a novel 2D metal–organic framework (MOF) with planar asymmetric N/O mixed coordinated Cu−N1O3 unit is constructed, labeled as BIT‐119. When applied to CO2RR, BIT‐119 could reach a CO2‐to‐C2 conversion with C2 partial current density ranging from 36.9 to 165.0 mA cm−2 in flow cell. Compared to the typical symmetric Cu−O4 units, asymmetric Cu−N1O3 units lead to the re‐distribution of local electron structure, regulating the adsorption strength of several key adsorbates and the following catalytic selectivity. From experimental and theoretical analyses, Cu−N1O3 sites could simultaneously couple the atop‐type (on Cu site) and bridge‐type (on Cu−N site) adsorption of *C1 species to reach the CO2‐to‐C2 conversion. This work broadens the feasible C−C coupling mechanism on 2D functional porous frameworks.

Preparation of NH2-MIL-101(Fe) Metal Organic Framework and Its Performance in Adsorbing and Removing Tetracycline.

Tetracycline's accumulation in the environment poses threats to human health and the ecological balance, necessitating efficient and rapid removal methods. Novel porous metal-organic framework (MOF) materials have garnered significant attention in academia due to their distinctive characteristics. This paper focuses on studying the adsorption and removal performance of amino-modified MIL-101(Fe) materials towards tetracycline, along with their adsorption mechanisms. The main research objectives and conclusions are as follows: (1) NH2-MIL-101(Fe) MOF materials were successfully synthesized via the solvothermal method, confirmed through various characterization techniques including XRD, FT-IR, SEM, EDS, XPS, BET, and TGA. (2) NH2-MIL-101(Fe) exhibited a 40% enhancement in tetracycline adsorption performance compared to MIL-101(Fe), primarily through chemical adsorption following pseudo-second-order kinetics. The adsorption process conformed well to Freundlich isotherm models, indicating multilayer and heterogeneous adsorption characteristics. Thermodynamic analysis revealed the adsorption process as a spontaneous endothermic reaction. (3) An increased adsorbent dosage and temperature correspondingly improved NH2-MIL-101(Fe)'s adsorption efficiency, with optimal performance observed under neutral pH conditions. These findings provide new strategies for the effective removal of tetracycline from the environment, thus holding significant implications for environmental protection.

Thermally Conductive Polydimethylsiloxane-Based Composite with a Three-Dimensional Vertically Aligned Thermal Network Incorporating Hexagonal Boron Nitride Nanosheets and Nanodiamonds.

Thermal interface materials play a pivotal role in efficiently transferring heat from heating devices to thermal management components, thereby reducing the risk of component degradation due to overheating. In this study, we propose a strategy for enhancing the out-of-plane thermal conductivity (TC) of composite materials by fabricating a three-dimensional (3D) thermal network within a polydimethylsiloxane (PDMS) matrix. Specifically, the composite material was designed to incorporate a dense thermal network comprising hexagonal boron nitride nanosheets (BNNSs) and nanodiamonds (NDs). The fabrication process commenced with the preparation of BNNSs through liquid-phase exfoliation, followed by the creation of a 3D BNNSs-NDs/polyimide aerogel thermal framework using a unidirectional solidification ice templating method and subsequent heat treatment. Vacuum impregnation and curing were then employed to finalize the production of the 3D BNNSs-NDs/PDMS composite material. Characterization analyses indicated that the addition of NDs filled the voids between BNNSs, leading to the densification of the thermal framework pore walls and the establishment of additional thermal pathways. Impressively, with concentrations of BNNSs and NDs of 17.99 and 7.71 wt %, respectively, the out-of-plane TC of the 3D BNNSs-NDs/PDMS composite material reached 1.623 W m-1 K-1, marking notable enhancements of 754.21% and 256.70% compared to those of pure PDMS and composites prepared via direct blending with randomly distributed BNNSs and NDs, respectively. Furthermore, the 3D BNNSs-NDs thermal framework improved the compressive strength and the dimensional stability of the composite material. Finite element simulations additionally confirmed the synergistic improvement of the TC achieved through the combination of BNNSs and NDs, demonstrating that the 3D BNNSs-NDs/PDMS composite material displayed superior heat conduction and a greater density of thermal pathways compared to those of its counterparts, including 3D BNNSs/PDMS and 3D NDs/PDMS composite materials. In summary, this work presents a strategy for enhancing the out-of-plane TC of polymer-based composite materials by incorporating vertically aligned thermal networks.

Enhancing CO2 adsorption performance of cold oxygen plasma-treated almond shell-derived activated carbons through ionic liquid incorporation

To enhance the CO2 adsorption of almond shell-derived activated carbon (AC) samples treated with cold oxygen plasma, the samples were impregnated with cholinium-amino acid ionic liquids ([Cho][AA] ILs) using the vacuum-assisted impregnation method. The physicochemical and textural properties of the resulting composites (ILs@AC) were characterized using various techniques, including Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM) coupled with energy-dispersive X-ray (EDX) spectroscopy, and Brunauer-Emmett-Teller (BET) surface area measurement. The CO2 adsorption performance of the samples was evaluated using a quartz crystal microbalance (QCM) over a temperature range of 288.15–308.15 K and gas pressures up to 1 bar. The IL@AC composite materials exhibited notably improved CO2 adsorption capacities compared to pristine AC. The CO2 adsorption isotherms onto the IL@AC composite samples closely conformed to the Langmuir isotherm model, indicating the dominant involvement of strong intermolecular interactions, particularly driven by amine functionalities. Meanwhile, the results revealed that [Cho][His]@AC showed lowered CO2 adsorption capacity compared to [Cho][Pro]@AC and [Cho][Gln]@AC. Among the studied ionic liquids, [Cho][Pro]@AC showed the highest absorption capacity (2.332 mmol·g−1 at 288 K and 1 bar). This was due to the obstruction of internal pores within the AC structure caused by excessive amine incorporation into its porous framework. In the meantime, for a deeper insight into the impregnation process of ILs onto the AC surfaces and their potential interactions with CO2 molecules, we conducted density-functional theory (DFT) calculations using the ωB97XD/6-31 + G(d,p) method. The calculated interaction energies, ranging from − 1.19 to − 1.44 eV, along with calculated quantum chemical descriptors, indicated a notable stabilization of IL species on the AC surfaces, with high affinity toward CO2 molecules.

Synergistic Enhancements of Zn-ZIF with Nano Zinc Oxide for Hydrogen adsorption, energy storage, and photocatalytic technologies

Creating the porous Zinc-Zeolitic Imidazolate Framework (Zn-ZIF) using a solvothermal technique addresses the need for advanced materials with distinctive properties and cost-effectiveness in modern applications. The PXRD, SEM, UV-DRS, TEM, and TGA/DTG are used to characterize different concentrations of Zn-ZIF. Zn-ZIF's crystalline structure and phase purity have been verified by PXRD. Using diffuse reflectance spectra, the Kubelka-Monk function determined the band gaps of the Zn-ZIF samples, and scanning electron microscopy revealed a more porous structure. At 77 K and 1 bar, the Zn-ZIF solution with a 2:1 ratio had the highest hydrogen storage capacity (1.71 wt%). The electrochemical behavior of several Zn-ZIF electrodes in a 6 M KOH electrolyte was evaluated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) experiments. The Zn-ZIF electrode with a 2:1 ratio exhibits a low charge transfer resistance and a high proton diffusion coefficient (D) of 1.687 × 10−4 cm2 s−1. The characteristics of the 2:1 synthesized Zn-ZIF electrode as a supercapacitor were investigated. Our analysis of the generated Zn-ZIF material's specific capacitance values after 2000 cycles revealed an impressive retention rate of nearly 89 %, with values of 296.6 Fg-1. In addition, we examined the photocatalytic activities of the as-synthesized material by exposing it to ultraviolet light and seeing how it degraded organic dyes such as Cango-Red (CR) dye. With a photocatalytic efficacy of 95.06 % for CR dye, Zn-ZIF (2:1 ratio) is the most effective. These findings should provide new knowledge for researchers interested in developing novel Zn-ZIF materials for photocatalytic, energy storage, and hydrogen storage applications.

Unlocking Fast Ionic Transport in Sub‐Nano Channels of MOF‐Based Electrolytes for Next‐Generation Batteries

AbstractIncorporating appropriate molecules into ordered porous framework materials plays a pivotal role in modulating their physicochemical properties and dynamic behaviors. Such frameworked materials are also applicable for the preparation of solid‐state electrolyte (SSE) with altered electrochemical performance. In this work, MOF (Metal‐Organic Framework)‐based frameworked electrolytes (FEs) are prepared by the introduction of conductive ion‐molecule complexes and have investigated the electrochemical behaviors. The angstrom‐level pores in the framework enable efficient interactions with the complexes and participation in ion transportation by altering the coordinating environments of Li+ ions. As a result, the activated MOF‐based SSE exhibits an impressive ionic conductivity of 4.0×10−4 S cm−1 at room temperature (RT), along with a notably reduced activation energy of 0.12 eV at 350 K. The MOF‐based FE has been applied to Li /FE /LiFePO4 batteries, which exhibit excellent long‐cycling performance with virtually no capacity loss over 1000 cycles at the current density of 2 C at RT. The novel Li+ transport mechanisms where ion‐molecules would actively participate in the interactions between the framework and Li+ ions, not only present a new strategy for enhancing the ion transport kinetics, but also deliver outstanding electrochemical performance promising for next‐generation batteries.

An Ultramicroporous Zinc‐Based Zeolitic Imidazolate Framework‐8 for the Adsorption of CO2, CH4, CO, N2 and H2: A Combined Experimental and Theoretical Study

AbstractAn alternative synthesis route to obtain ultramicroporous zeolitic imidazolate framework‐8 (ZIF‐8) is reported that is rapid and does not require organic solvent or heating. The polyethylene glycol‐templated ZIF‐8 nanoparticles (<50 nm size) exhibited a high BET (Brunauer, Emmett and Teller) surface area of 1853 m2/g, a total pore volume of 0.73 cm3/g, and 0.54 nm ultramicropores. A new approach is introduced here to better understand gas adsorption in porous metal organic frameworks (MOFs) that combines theoretical and experimental isotherm data obtained for five gases with statistical physics modelling. The multiscale analytical model reveals that the gas molecules, irrespective of their structure, adsorb in a mixed orientation at low temperature, and a parallel multi‐molecular orientation at higher temperature. The number of gas molecules adsorbed per site ranged from 0.83–2.2 while the number of adsorbent layers ranged between 1.4–5.6, depending on the gas and the temperature. The multilayer adsorption processes involved adsorption energies from 2.85 kJ/mol–9.77 kJ/mol for all gases, consistent with physisorption via van der Waals and London dispersion forces. The initial adsorption energies were higher and therefore stronger. A particularly high capacity for CO2 of 1088 mg(CO2)/g at 298 K was observed while H2 adsorption was only 9 mg(H2)/g. The other gases adsorbed at 145 mg/g–245 mg/g at 298 K. Thermodynamic functions that governed the adsorption process such as the internal energy, the enthalpy, and Gibbs free energy, are also reported, as well as the adsorption entropies, for the 5 gases.

BaFe12O19 Functional Porous Carbon Nanocomposite as an Electrocatalyst of the Oxygen Reduction Reaction

AbstractIt is crucial to develop a non‐precious metal catalyst with high efficiency, affordable cost, and minimal environmental impact for conducting research on the oxygen reduction reaction (ORR) in fuel cells. In this study, BaFe12O19 functional porous carbon (BaFe12O19/PC) nanocomposite was successfully prepared using Fe2O3, BaCO3 and glucose as precursors. Meanwhile, the BaFe12O19/PC catalyst‐modified glassy carbon electrode, carbon rod, and Hg/HgO electrode were used as the working electrode, counter electrode, and reference electrode, respectively, to investigate the electrochemical behavior. The uniform distribution of nano‐scale BaFe12O19 particles in a porous carbon framework was confirmed by field emission scanning electron microscopy characterization. In addition, a double‐layer interface (Fe/Fe3C) was formed between the porous carbon and the nano‐sized BaFe12O19 particles. Fe/Fe3C has a synergistic effect with C, facilitating the migration and transfer of electrons from BaFe12O19 to porous carbon. The BaFe12O19/PC nanocomposite exhibited a four‐electron pathway for electrocatalytic kinetics, showcasing a significantly elevated half‐wave potential of 0.77 V, an impressively reduced Tafel slope of 84.95 mV/dec, and exceptional tolerance towards methanol. It is important to highlight that the BaFe12O19/PC nanocomposite not only possess high catalytic activity for oxygen reduction reactions (ORR), but also demonstrate excellent stability. Consequently, this synthesized BaFe12O19/PC nanocomposite hold promising prospects as cost‐effective and efficient catalysts in fuel cell applications.