Adsorption and Diffusion of Benzene in Mg-MOF-74 with Open Metal Sites

Recent Advances in Hierarchical Porous Engineering of MOFs and Their Derived Materials for Catalytic and Battery: Methods and Application

Hierarchical porous materials have attracted the attention of researchers due to their enormous specific surface area, maximized active site utilization efficiency, and unique structure and properties. In this context, metal-organic frameworks (MOFs) offer a unique mix of properties that make them particularly appealing as tunable porous substrates containing highly active sites. This review focuses on recent advances in the types and synthetic strategies of hierarchical porous MOFs and their derived materials. Furthermore, it highlights the relationship between the mass diffusion and transport of hierarchical porous structures and the pore size with examples and simulations, while identifying their potential and limitations. On this basis, how the synthesis conditions affect the structure and electrochemical properties of MOFs based hierarchical porous materials with different structures is discussed, highlighting the prospects and challenges for the synthetization, as well as further scientific research and practical applications. Finally, some insights into current research and future design ideas for advanced MOFs based hierarchical porous materials are presented.

Elucidating the Competitive Adsorption of H2O and CO2 in CALF-20: New Insights for Enhanced Carbon Capture Metal-Organic Frameworks

In light of the pressing need for efficient carbon capture solutions, our study investigates the simultaneous adsorption of water (H2O) and carbon dioxide (CO2) as a function of relative humidity in CALF-20, a highly scalable and stable metal-organic framework (MOF). Advanced computer simulations reveal that due to their similar interactions with the framework, H2O and CO2 molecules compete for the same binding sites, occupying similar void regions within the CALF-20 pores. This competition results in distinct thermodynamic and dynamical behaviors of H2O and CO2 molecules, depending on whether one or both guest species are present. Notably, the presence of CO2 molecules forces the H2O molecules to form more connected hydrogen-bond networks within smaller regions, slowing water reorientation dynamics and decreasing water entropy. Conversely, the presence of water speeds up the reorientation of CO2 molecules, decreases the CO2 entropy, and increases the propensity for CO2 to be adsorbed within the framework due to stronger water-mediated interactions. Due to the competition for the same void spaces, both H2O and CO2 molecules exhibit slower diffusion when molecules of the other guest species are present. These findings offer valuable strategies and insights into enhancing the differential affinity of H2O and CO2 for MOFs specifically designed for carbon capture applications.

Dynamical and electronic properties of anion-pillared metal-organic frameworks for natural gas separation

The increasing demand for natural gas as a clean energy source has emphasized the need for efficient gas separation technologies. Metal-organic frameworks (MOFs) have emerged as a promising class of materials for gas separation, with anion-pillared MOFs (APMOFs) gaining attention for their fine-tuned pore design and shape/size selectivity. In this study, we investigate the dynamical and electronic properties of three APMOFs, SIFSIX-3-Cu, SIFSIX-2-Cu-i, and SIFSIX-2-Cu, for the separation of methane from ethane, ethene, propane, propene, and N using computational simulations. Our simulations employ Grand Canonical Monte Carlo (GCMC) and Molecular Dynamics (MD) techniques combined with Density Functional Theory (DFT) calculations. We find that that all three APMOFs exhibit promising separation capabilities for methane from propane and propene based on both thermodynamics and kinetics parameters. In addition, we use Noncovalent Interaction (NCI) analysis to investigate intermolecular interactions and find that the fluorine atoms in the MOF can polarize gas molecules and establish electrostatic interactions with hydrogen atoms in the molecule. Finally, we show that SIFSIX-2-Cu-i is a potential candidate for separating N2/CH4 due to its interpenetration.

Defective MOF-74 with ancillary open metal sites for the enhanced adsorption of chemical warfare agent simulants

The development of effective porous adsorbents plays a vital role in eliminating hazardous substances from the environment. Toxic chemicals, including chemical warfare agents (CWAs), pose significant risks to both humans and ecosystems, highlighting the urgency to create efficient porous adsorbents. Therefore, substantial attention has been directed towards advancing adsorption techniques for the successful eradication of CWAs from the environment. Herein, we demonstrate a rational approach for enhancing the adsorption capability of a porous metal-organic framework (MOF) by employing ancillary open metal sites within the MOF structure. To generate defective MOF-74 (D-MOF-74) with ancillary open metal sites, some of the 2,5-dihydroxy-1,4-bezenedicarboxylic acid (DHBDC) linkers originally present in the MOF-74 structure were replaced with 1,4-benzenedicarboxylic acid (BDC) linkers. The absence of hydroxyl groups in the BDC linkers compared to the original DHBDC linkers creates ancillary open metal sites, which enhance the adsorption ability of D-MOF-74 for CWA simulants such as dimethyl methyl phosphonate, 2-chloroethyl ethyl sulfide, and methyl salicylate by providing effective interaction sites for the targeted molecules. However, excessive creation of open metal sites causes the collapse of the originally well-developed MOF-74 structure, resulting in a substantial reduction in its empty space and a subsequent decline in adsorption efficiency. Thus, to produce a defective MOF with the best performance, it is necessary to replace an appropriate amount of organic linker and create suitable open metal sites. Moreover, D-MOF-74 displays excellent recyclability during consecutive adsorption cycles without losing its original structure and morphology, suggesting that D-MOF-74 is an effective and stable material for the removal of CWA simulants.

(FeMnCe)-co-doped MOF-74 with significantly improved performance for overall water splitting

Developing inexpensive electrocatalysts with high activity and stability is of great value for overall water splitting. In this work, we designed a series of 3d-4f (FeMnCe)-trimetallic MOF-74 with different ratios of 3d- and 4f-metal centers. Among them, FeMn6Ce0.5-MOF-74/NF exhibited the best electrocatalytic performance for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in an alkaline solution. It only requires a low overpotential of 281 mV@100 mA cm-2 for OER and 186 mV@-10 mA cm-2 for HER in 1 M KOH. With FeMn6Ce0.5-MOF-74/NF as the anode and cathode in the overall water splitting system, only 1.65 V is needed to deliver a current density of 10 mA cm-2. In particular, for the as-fabricated FeMn6Ce0.5-MOF-74/NF||Pt/C cell unit, only 1.40 V is needed to achieve 10 mA cm-2. Therefore, the successful design of 3d-4f mixed-metallic MOF-74 provides a new viewpoint to develop highly efficient non-precious metal electrocatalysts.

Synthesis of an IRMOF-1@SiO2 Core-Shell and Amino-Functionalization with APTES for the Adsorption of Urea and Creatinine Using a Fixed-Bed Column Study

Kidney dysfunction is a clinical disease that disables the kidneys to remove the waste products and uremic toxins from the circulation and may lead to fatal kidney failure. Hemodialysis is advantageous in this circumstance since it prevents the accumulation of waste products in the body and facilitates the removal of uremic toxins. However, hemodialysis cannot entirely remove some uremic toxins, such as urea and creatinine. In this paper, a high-performance fixed-bed column for urea and creatinine removal was offered. As a result, a MOF layer was built on SiO₂, which was then amino-functionalized using APTES. Numerous assays were used to characterize the final adsorbent. The adsorption of urea and creatinine was evaluated in batch and continuous conditions. Thus, it was demonstrated that the adsorption behavior of A(0.2)-IRMOF-1@SiO₂ followed the Langmuir isotherm, and it exhibited the maximum adsorption capacity. The batch experiment determined that urea and creatinine had an adsorption capacity of 1325.73 and 625.00 mg·g^-1, respectively. The adsorption capacity was increased, which was due to the presence of amino groups (APTES) on the MOF surface. The continuous operation was evaluated using the A(0.2)-IRMOF-1@SiO₂ fixed-bed column. Thomas and Nelson's models were examined to achieve a better understanding of the adsorption behaviors. The A(0.2)-IRMOF-1@SiO₂ fixed-bed column successfully removed 92.57% of urea and 80.47% of creatinine. The separation factor for urea in comparison to creatinine was 2.40 in the A(0.2)-IRMOF-1@SiO₂ fixed-bed column.

The Complexity of Comparative Adsorption of C6 Hydrocarbons (Benzene, Cyclohexane, n-Hexane) at Metal-Organic Frameworks

The relatively stable MOFs Alfum, MIL-160, DUT-4, DUT-5, MIL-53-TDC, MIL-53, UiO-66, UiO-66-NH₂, UiO-66(F)₄, UiO-67, DUT-67, NH₂-MIL-125, MIL-125, MIL-101(Cr), ZIF-8, ZIF-11 and ZIF-7 were studied for their C₆ sorption properties. An understanding of the uptake of the larger C₆ molecules cannot simply be achieved with surface area and pore volume (from N₂ sorption) but involves the complex micropore structure of the MOF. The maximum adsorption capacity at p p₀^-1 = 0.9 was shown by DUT-4 for benzene, MIL-101(Cr) for cyclohexane and DUT-5 for n-hexane. In the low-pressure range from p p₀^-1 = 0.1 down to 0.05 the highest benzene uptake is given by DUT-5, DUT-67/UiO-67 and MIL-101(Cr), for cyclohexane and n-hexane by DUT-5, UiO-67 and MIL-101(Cr). The highest uptake capacity at p p₀^-1 = 0.02 was seen with MIL-53 for benzene, MIL-125 for cyclohexane and DUT-5 for n-hexane. DUT-5 and MIL-101(Cr) are the MOFs with the widest pore window openings/cross sections but the low-pressure uptake seems to be controlled by a complex combination of ligand and pore-size effect. IAST selectivities between the three binary mixtures show a finely tuned and difficult to predict interplay of pore window size with (critical) adsorptive size and possibly a role of electrostatics through functional groups such as NH₂.

Adsorption and Self-Diffusion of R32/R1234yf in MOF-200 Nanoparticles by Molecular Dynamics Simulation

The thermophysical properties of a refrigerant can be modified via adding metal organic frameworks (MOF) to it. Understanding the adsorption–diffusion process of the mixture in MOFs at the molecular level is important to further improve the efficiency of the organic Rankine cycle. The adsorption and diffusion of R32/R1234yf in MOF-200 was investigated by molecular dynamics simulation in the present work. The results show that the number of adsorbed molecules of R32 in MOF-200 per unit mass is higher than that of R1234yf in the pure fluid adsorption system. The adsorption capacity of the mixture is lower than that of a pure working medium due to competitive adsorption. For both pure and mixed refrigerants, the adsorption heat of R32 in MOF-200 is smaller than that of R1234yf. Compared with R1234yf, the self-diffusion coefficient of R32 in MOF-200 is larger because of the lower diffusion activation energy.

Separation of Volatile Organic Compounds in TAMOF-1

Separation of volatile organic compounds is one of the most studied processes in industry. TAMOF-1 is a homochiral metal-organic framework with a crystalline network of interconnected ≈1 nm channels and has high thermal and chemical stability. Thanks to these features, it can resolve racemic mixtures of chiral drugs as a chiral stationary phase in chromatography. Interestingly, the particular shape and size of its channels, along with the presence of metallic centers and functional groups, allow establishing weak but significant interactions with guest molecules. This opens interesting possibilities not only to resolve racemates but also to separate other organic mixtures, such as saturated/unsaturated and/or linear/branched molecules. In search of these applications, we have studied the separation of volatile organic compounds in TAMOF-1. Monte Carlo simulations in the grand-canonical ensemble have been carried out to evaluate the separation of the selected molecules. Our results predict that TAMOF-1 is able to separate xylene isomers, hexane isomers, and benzene-cyclohexane mixtures. Experimental breakthrough analysis in the gas phase and also in the liquid phase confirms these predictions. Beds of TAMOF-1 are able to recognize the substitution in xylenes and the branching in hexanes, yielding excellent separation and reproducibility, thanks to the chemical and mechanical features of this material.

Facile synthesis of magnesium-based metal-organic framework with tailored nanostructure for effective volatile organic compounds adsorption

A novel Mg(II) metal-organic framework (Mg-MOF) was synthesized based on the ligand of 2,2'-bipyridine-4,4'-dicarboxylic acid. Single-crystal X-ray structural analysis confirmed that three-dimensional-nanostructure Mg-MOFs formed a monoclinic system with a channel size of 15.733 Å × 23.736 Å. N₂ adsorption isotherm, Fourier transform infrared spectroscopy, thermogravimetric analysis and high-resolution transmission electron microscopy were performed to characterize the thermal stability and purity of the Mg-MOFs. The adsorption studies on four typical volatile organic compounds (VOCs) emitted during wood drying showed that Mg-MOFs have noteworthy adsorption capacities, especially for benzene and β-pinene with adsorptions of 182.26 mg g^-1 and 144.42 mg g^-1, respectively. In addition, the adsorption of Mg-MOFs mainly occurred via natural adsorption, specifically, multi-layer physical adsorption, accompanied by chemical forces, which occurred in the pores where the VOCs molecules combined with active sites. As an adsorbent, Mg-MOFs exhibit versatile behaviour for toxic gas accumulation.

Reactive Grand-Canonical Monte Carlo Simulations for Modeling Hydration of MgCl2

Thermochemical heat-storage applications, based on the reversible endo-/exothermic hydration reaction of salts, are intensively investigated to search for compact heat-storage devices. To achieve a truly valuable storage system, progressively complex salts are investigated. For these salts, the equilibrium temperature and pressure conditions are not always easy to predict. However, these conditions are crucial for the design of thermochemical heat-storage systems. A biased grand-canonical Monte Carlo (GCMC) tool is developed, enabling the study of equilibrium conditions at the molecular level. The GCMC algorithm is combined with reactive force field molecular dynamics (ReaxFF), which allows bond formation within the simulation. The Weeks-Chandler-Andersen (WCA) potential is used to scan multiple trial positions for the GCMC algorithm at a small cost. The most promising trial positions can be selected for recomputation with the more expensive ReaxFF. The developed WCA-ReaxFF-GCMC tool was used to study the hydration of MgCl2·nH2O. The simulation results show a good agreement with experimental and thermodynamic equilibriums for multiple hydration levels. The hydration shows that water, present at the surface of crystalline salt, deforms the surface layers and promotes further hydration of these deformed layers. Additionally, the WCA-ReaxFF-GCMC algorithm can be used to study other, non-TCM-related, reactive sorption processes.

Porous structured cotton-based ACF for the adsorption of benzen

Fibrous activated carbon has attracted emerging research interests due to its remarkable adsorption performance for volatile organic compounds (VOCs). Though this adsorption behavior for VOCs is closely related to the pore structure on the surface of activated carbon fiber (ACF), few researchers paid attentions to the influence of textural properties of this adsorption process. Especially, cotton-based activated carbon fiber (CACF) for adsorbing benzene pollutant is rarely reported. Herein, in order to develop a high-performance adsorbent for the removal of VOCs pollutants, this work studied the influence of textural properties of CACF on the adsorption of benzene. The results showed that the increase of carbonization temperature would lead to the reduction of mesopores but the increase of micropores for CACF; the embedment of phosphoric acid and its derivatives into the carbon layers contributed to the formation of pore structure for CACF; furthermore, specific surface area of CACF can also be enlarged by increasing the concentration of phosphoric acid. More importantly, it was found that the adsorption capacity of CACF for benzene was strongly dependent on the specific surface area and volume of micropores within CACF because micropores can provide more favorable binding sites. This adsorption process preferred to occur on the wall of micropores, then the accumulated benzene would slowly fill the pores. Interestingly, the decrease of pore size of micropores can unexpectedly improve the affinity of CACF to benzene on the contrary. This work provides a new strategy to develop porous structured ACF materials for the high-performance adsorption of VOCs.

Nanoconfinement and mass transport in metal-organic frameworks

The ubiquity of metal-organic frameworks in recent scientific literature underscores their highly versatile nature. MOFs have been developed for use in a wide array of applications, including: sensors, catalysis, separations, drug delivery, and electrochemical processes. Often overlooked in the discussion of MOF-based materials is the mass transport of guest molecules within the pores and channels. Given the wide distribution of pore sizes, linker functionalization, and crystal sizes, molecular diffusion within MOFs can be highly dependent on the MOF-guest system. In this review, we discuss the major factors that govern the mass transport of molecules through MOFs at both the intracrystalline and intercrystalline scale; provide an overview of the experimental and computational methods used to measure guest diffusivity within MOFs; and highlight the relevance of mass transfer in the applications of MOFs in electrochemical systems, separations, and heterogeneous catalysis.

A decomposition mechanism for Mn2(DSBDC) metal-organic frameworks in the presence of water molecules

In this work, we investigate the effects of water on the structural stability of Mn₂(DSBDC) metal-organic framework (MOF) using DFT-based calculations. It has been found that the adsorption of multiple water molecules forming a hydrogen bond network around the Mn centers plays an important role in the decomposition process. Different effects contribute to the destabilization of the MOF: water molecules that directly coordinate to the open sites displayed by a part of the Mn centers can induce a significant shift in the charge distribution as indicated by the analysis of charge density differences and the Bader charges. This adsorption process leads to a slight elongation of the metal-linker bonds. The direct interaction with the Mn center is the most stable adsorption mode for water in Mn₂(DSBDC). Once these adsorption sites at the Mn centers are fully occupied, additional water molecules start to bind via hydrogen bonds to the already present water molecules or, more importantly, to the linker molecules. This, in return, leads to a significant weakening of the Mn-linker bonds, thus allowing water insertion into the Mn-linker bonds with a barrier of only 0.16 eV, which is believed to initiate the decomposition of the Mn₂(DSBDC) framework. Based on a kinetic Monte Carlo model, it can be shown that high temperatures can prevent the adsorption of water molecules around the Mn sites and thus slow down the MOF decomposition.

Defect engineering-induced porosity in graphene quantum dots embedded metal-organic frameworks for enhanced benzene and toluene adsorption

The emerging environmental issues necessitate the engineering of novel and well-designed nanoadsorbents for advanced separation and purification applications. Despite recent advances, the facile synthesis of hierarchical micro-mesoporous metal-organic frameworks (MOFs) with tuned structures has remained a challenge. Herein, we report a simple defect engineering approach to manipulate the framework, induce mesoporosity, and crease large pore volumes in MIL-101(Cr) by embedding graphene quantum dots (GQDs) during its self-assembly process. For instance, MIL-101@GQD-3 (V_meso: 0.68 and V_tot: 1.87 cm³/g) exhibited 300.0% and 53.3% more meso and total pore volume compared to those of the conventional MIL-101 (V_meso: 0.17 and V_tot: 1.22 cm³/g), respectively, resulting in 1.7 and 2.8 times greater benzene and toluene loading at 1 bar and 25 °C. In addition, we found that MIL-101@GQD-3 retained its superiority over a wide range of VOC concentrations and operating temperature (25-55 °C) with great cyclic capacity and energy-efficient regeneration. Considering the simplicity of the adopted technique to induce mesoporosity and tune the nanoporous structure of MOFs, the presented GQD incorporation technique is expected to provide a new pathway for the facile synthesis of advanced materials for environmental applications.

Synthesis of High-Quality Mg-MOF-74 Thin Films via Vapor-Assisted Crystallization

The unique features of metal-organic frameworks (MOFs), such as their large surface areas and diversity of structures, make them suitable for a broad range of applications including storage, separation, and sensing of gases. Among all the MOFs, Mg-MOF-74 with the highest CO₂ uptake at 1 bar and 25 °C would be particularly beneficial for CO₂-related applications. One of the most critical enabling technologies for implementing Mg-MOF-74 is the preparation of dense and continuous films that would maximize the sorption behaviors. However, Mg-MOF-74 thin films present significant challenges in demonstrating large-scale coatings. Herein, we demonstrate for the first time high-quality Mg-MOF-74 films synthesized via a vapor-assisted crystallization (VAC) process. The VAC process described herein provides dense and highly crystalline layers of the Mg-MOF-74 thin film with a low coefficient of variation of film thickness below 7%. By minimizing the solvent use, the VAC process is also more environmentally friendly than conventional techniques. In this work, we first optimized a precursor solution for the VAC process and then investigated the effects of synthesis temperature, time, and droplet volume on the growth, crystallinity, and thickness of VAC Mg-MOF-74 films. The porosity of the MOF film was assessed by measuring the CO₂ uptake at room temperature and 1 bar. The obtained VAC Mg-MOF-74 films possess a well-defined microporosity, as deduced from CO₂ adsorption studies via quartz crystal microbalance (QCM) and comparison with bulk Mg-MOF-74 reference data. Furthermore, CO₂ cyclic adsorption-desorption experiments on the VAC Mg-MOF-74 films showed scaled uptakes to a wide range of CO₂ concentration without showing significant variations in the baseline. We specifically demonstrate how the film's quality of the MOF affects adsorption behavior of CO₂ on VAC Mg-MOF-74 and drop-cast Mg-MOF-74 films.

Flexible amorphous metal-organic frameworks with π Lewis acidic pore surface for selective adsorptive separations

Selective separation of light hydrocarbons (LHs) and adsorption of volatile organic compounds (VOCs) remain expensive and complex scientific challenges in the petrochemical industry. Shape-selective adsorbent materials can cost-effectively face these demands. Two new porous, dynamic and amorphous metal-organic frameworks (MOFs), NEU-3 [= Zn(PMDA)(Py)2] and NEU-4 [= Fe(PMDA)(Py)2] are disclosed. These MOFs along with NEU-1c [= Zn(BPDI)(Py)2] and NEU-2 [= Fe(BPDI)(Py)2] display an electron-deficient pore surface due to predesigned π-electron-deficient ligands. They are unique smart guest-responsive materials owing to their π Lewis acidic pore surface and presumably their framework flexibility. A variety of effective adsorptions and adsorptive separations is achieved by using beds of NEU-1c, NEU-2, NEU-3 and NEU-4. Promising for further investigations into the petrochemical industry, NEU-4 shows ultrahigh benzene adsorption, recognition capability, selectivity for benzene over its analogues, and high stability and regenerability.

Fiber-Based Gas Filter Assembled via In Situ Synthesis of ZIF-8 Metal Organic Frameworks for an Optimal Adsorption of SO2: Experimental and Theoretical Approaches

For environmental protection from exposure to airborne toxic gases, metal organic frameworks (MOFs) have drawn great attention as gas adsorbent options, with their advantages in chemical tailorability and large porosity. To develop a fiber-based gas filter that is effective against SO₂ gas, zeolite imidazole framework-8 (ZIF-8) was applied to polypropylene nonwoven by various methods. Among the tested methods, the sol-gel impregnation method showed the highest ZIF-8 loading efficiency. There existed an optimal loading of ZIF-8 for the maximum adsorption efficiency, and it was associated with the accessibility of gas molecules to the ZIF-8 pores and active sites. Dominant adsorption processes and mechanisms were investigated by fitting the theoretical sorption models to experimental data. The results demonstrate that the increased ZIF-8 loading to fibers, beyond a certain level, may hinder the diffusivity and increase the barrier effect, eventually decreasing the adsorption efficiency. This study is novel and significant in that a multifaceted approach, including experimental analysis, theoretical investigation, and computational modeling, was made for scrutinizing the intricate phenomena occurring in the gas sorption process. The results of this study provide the fundamental yet practical information on the manufacturing considerations for the optimal design of MOF-loaded fibrous adsorbents.

A highly stable metal–organic framework with cubane-like clusters for the selective oxidation of aryl alkenes to aldehydes or ketones

A novel MOF with cubane-like clusters was prepared based on an electron-deficient triazine derivative, and it exhibits excellent thermal and chemical stability and can be used for the selective oxidation of aryl alkenes to aldehydes or ketones in mild conditions.

In situ growth of well-aligned Ni-MOF nanosheets on nickel foam for enhanced photocatalytic degradation of typical volatile organic compounds

Exploitation of highly efficient catalysts for photocatalytic degradation of volatile organic compounds (VOCs) under visible light irradiation is highly desirable yet challenging. Herein, well-aligned 2D Ni-MOF nanosheet arrays vertically grown on porous nickel foam (Ni-MOF/NF) without lateral stacking were successfully prepared via a facile in situ solvothermal strategy. In this process, Ni foam could serve as both a skeleton to vertically support the Ni-MOF nanosheets and a self-sacrificial template to afford Ni ions for MOF growth. The Ni-MOF/NF nanosheet arrays with highly exposed active sites and light harvesting centres as well as fast mass and e- transport channels exhibited excellent photocatalytic oxidation activity and mineralization efficiency to typical VOCs emitted from the paint spray industry, which was almost impossible for their three-dimensional (3D) bulk Ni-MOF counterparts. A mineralization efficiency of 86.6% could be achieved at 98.1% of ethyl acetate removal. The related degradation mechanism and possible reaction pathways were also attempted based on the electron paramagnetic resonance (EPR) and online Time-of-Flight Mass Spectrometer (PTR-ToF-MS) results.

Separation of CF4/N2, C2F6/N2, and SF6/N2 Mixtures in Amorphous Activated Carbons Using Molecular Simulations

The capture and separation of CF₄, C₂F₆, and SF₆ and their mixtures containing nitrogen is a challenging process. To solve this, we propose the use of saccharose coke-based carbons as membranes for the adsorption and separation of these gases. By means of advanced techniques of Monte Carlo and molecular dynamics simulations, we have studied the adsorption and diffusion of CF₄, C₂F₆, and SF₆ as well as their mixtures with nitrogen in three HRMC carbon models, namely, CS400, CS1000, and CS1000a. We have computed the adsorption isotherms of the single components and the heat of adsorption as a function of the adsorbed concentration. We have also calculated the competitive adsorption of fluoride molecules and nitrogen at two different molar fractions, 0.1 and 0.9. We have computed the transport properties of the adsorbed gases in terms of the self-diffusivities and corrected diffusivities. The performance of the membranes for the targeted separations has been characterized by the calculation of the permselectivity. Our results indicate that the activated amorphous carbon CS1000a is an efficient adsorbent for the capture of the fluoride adsorbates as well as their purification from nitrogen-based mixtures.

Zeolitic Imidazolate Framework-Based Composite Incorporated with Well-Dispersed CoNi Nanoparticles for Efficient Catalytic Reduction Reaction

Incorporation of metal nanocatalysts within a well-defined porous support is of great importance for stabilizing unstable metal nanocatalysts, so that they display an effective and long-lasting catalytic activity. In particular, metal-organic frameworks (MOFs) with a wide range of structures serve as excellent porous supports for stabilizing unstable nanocatalysts. In addition, the development of inexpensive metal nanocatalysts is necessary to replace expensive noble metal nanocatalysts. Herein, we report on a simple method for the preparation of porous MOF-based or carbon-based composites incorporated with catalytically active CoNi alloy nanoparticles. CoNi alloy nanoparticles were produced from the concurrent reduction of Co and Ni ions existing within a zeolitic imidazolate framework (ZIF)-based precursor material during the thermal treatment. In particular, a part of the highly porous ZIF was preserved during the thermal treatment at 400 °C, which eventually resulted in a composite of ZIF and CoNi (CoNi@ZIF). The resulting CoNi@ZIF showed excellent catalytic activity for the reduction of 4-nitrophenol to 4-aminophenol. The synergy between the highly porous ZIF support and the well-dispersed CoNi nanoparticles within CoNi@ZIF provided an outstanding catalytic performance, even with inexpensive transition-metal nanocatalysts. Moreover, the catalytic activity of CoNi@ZIF was well conserved even after five consecutive reactions.

In situ decorated MOF-derived Mn–Fe oxides on Fe mesh as novel monolithic catalysts for NOx reduction

In situ decorated MOF-derived Mn–Fe oxides on Fe mesh were developed as novel monolithic catalysts for NO_x reduction.