One‐stage Template‐free KOH Activation for Mesopore‐enriched Carbons and Their Application in CO2 Capture

Activated carbons with a high mesoporous structure were prepared by a one‐stage KOH activation process without the assistance of templates and further used as adsorbents for CO₂ capture. The physical and chemical properties as well as the pore structures of the resulting mesoporous carbons were characterized by N₂ adsorption isotherms, scanning electron microscopy (SEM ), X‐ray diffraction (XRD ), Raman spectroscopy, and Fourier transform infrared (FTIR ) spectroscopy. The activated carbon showed greater specific surface area and mesopore volume as the activation temperature was increased up to 600°C, showing a uniform pore structure, great surface area (up to ~815 m²/g), and high mesopore ratio (~55%). The activated sample exhibited competitive CO₂ adsorption capacities at 1 atm pressure, reaching 2.29 and 3.4 mmol/g at 25 and 0°C, respectively. This study highlights the potential of well‐designed mesoporous carbon as an adsorbent for CO₂ removal and widespread gas adsorption applications.     

Preparation of activated carbons and their adsorption properties for greenhouse gases: CH4 and CO2

Three kinds of activated carbons were prepared using coconut-shells as carbon precursors and characterized by XRD, FT-IR and texture property test. The results indicate that the prepared activated carbons were mainly amorphous and only a few impurity groups were adsorbed on their surfaces. The texture property test reveals that the activated carbons displayed different texture properties, especially the micropore size distribution. The adsorption capacities of the activated carbons were investigated by adsorbing CH4, CO2, N2 and O2 at 25 ?C in the pressure range of 0-200 kPa. The results reveal that all the activated carbons had high CO2 adsorption capacity, one of which had the highest CO2 adsorption value of 2.55 mmol/g at 200 kPa. And the highest adsorption capacity for CH4 of the activated carbons can reach 1.93 mmol/g at 200 kPa. In the pressure range of 0-200 kPa, the adsorption capacities for N2 and O2 were increased linearly with the change of pressure and K-AC is an excellent adsorbent towards the adsorption separation of greenhouse gases.     

树脂基球状活性炭的制备及对二氧化碳吸附性能的研究

以四种离子交换树脂（两种强碱性树脂D201和D280、两种弱碱性树脂D301G和D301R）为原料,经过磺化、炭化、活化处理制备了树脂基球状活性炭。采用TG、SEM、N₂吸附等对球状活性炭的收率、表面形貌、比表面积进行了表征,研究了所制球状活性炭对CO₂的吸附性能。结果表明,磺化处理有助提高树脂球的炭化收率;得到的四种球状活性炭对CO₂吸附性能良好,强碱性树脂球原料比弱碱性树脂球更具有优势,其中,由强碱性树脂球D201制得的树脂球状活性炭在30 ℃下对CO₂的吸附量可达2.57 mmol/g;十次循环吸附之后,树脂球仍能保持很好的CO₂吸附性能。     

Thermoregulated Phase‐Transition Synthesis of Two‐Dimensional Carbon Nanoplates Rich in sp2 Carbon and Unimodal Ultramicropores for Kinetic Gas Separation

The development of highly selective, chemically stable and moisture‐resistant adsorbents is a key milestone for gas separation. Porous carbons featured with random orientation and cross‐linking of turbostratic nanodomains usually have a wide distribution of micropores. Here we have developed a thermoregulated phase‐transition‐assisted synthesis of carbon nanoplates with more than 80 % sp² carbon, unimodal ultramicropore and a controllable thickness. The thin structure allows oriented growth of carbon crystallites, and stacking of crystallites in nearly parallel orientation are responsible for the single size of the micropores. When used for gas separation from CH₄, carbon nanoplates exhibit high uptakes (5.2, 5.3 and 5.1 mmol g^?1) and selectivities (7, 71 and 386) for CO₂, C₂H₆ and C₃H₈ under ambient conditions. The dynamic adsorption capacities are close to equilibrium uptakes of single components, further demonstrating superiority of carbon nanoplates in terms of selectivity and sorption kinetics.     

Recovering methane from quartz sand-bearing hydrate with gaseous CO_2

The replacement method by CO_2 is regarded as a new approach to natural gas hydrate(NGH) exploitation method, by which methane production and carbon dioxide sequestration might be obtained simultaneously. In this study, CO_2 was used to recover CH_4 from hydrate reservoirs at different temperatures and pressures. During the CO_2–CH_4 recovery process, the pressure was selected from 2.1 to 3.4 MPa, and the temperature ranged from 274.2 to 281.2 K. Calculating the fugacity differences between the gas phase and the hydrate phase for CO_2 and CH_4 at different conditions, it has found rising pressure was positive for hydrates formation process that was helpful for the improvement of CH_4 recovery rate. Rising temperature promoted the trend of CH_4 hydrate decomposition for the whole process of CO_2–CH_4replacement.The highest recovery rate was 46.6 % at 3.4 MPa 281.2 K for CO_2–CH_4replacement reaction in this work.     

A compare review about equilibrium conditions of semi-clathrate hydrate: experimental measurements visions and thermodynamic modeling aspects

The formation of gaseous (gas) hydrates for storage, separation and transportation application is essential. In this regard, a comprehensive study of this case is essential. Semi-clathrate hydrates have higher temperature stability and are formed in a stable range. The purpose of this study is review the experimental and modeling of the semi-clathrate hydrates, to investigate the equilibrium conditions for the formation/dissociation of them based on the type of thermodynamic promoters like TBAB, TBAC, TBAF, TBANO₃ and TBP groups. This review is consist of 4 overall section, at first an introduction to semi-clathrate hydrates has defined. After that, the experimental research has discussed through different gas systems such as CO₂, CH₄, N₂, H₂ etc. Also, the target of each study, like the CO₂ capture, separation of CH4, formation/dissociation equilibrium conditions, are expressed. Then, in the modeling section, the different types of thermodynamic modeling like, equaling fugacity, intelligence computing, Gibbs free energy minimization and Chen-Guo method are collected. At final section, a comparison between types of promoter showed that the addition of TBAF to aqueous solution has the best promotion effect on the CO₂ clathrate hydrate formation. Also, the results of comparing the concentration of promoters have shown that up to a certain amount of TBAB, the salt's role as a promoter and by addition concentration of promoter, has an inhibition effect. Also, besides the results of the comparison different promoters on equilibrium conditions of different gaseous hydrates, have indicated that, TBAB has the most significant impact on carbon dioxide hydrate.

     

Fabricating pyridinic N-B sites in porous carbon as efficient metal-free electrocatalyst in conversion CO2 into CH4

Electrochemical reduction of CO₂ (CO₂RR) to value-added chemicals is an attractive strategy for greenhouse gas mitigation and carbon recycle. Carbon material is one of most promising electrocatalysts but its product selectivity is limited by few modulating approaches for active sites. Herein, the predominant pyridinic N-B sites (accounting for 80% to all N species) are fabricated in hierarchically porous structure of graphene nanoribbons/amorphous carbon. The graphene nanoribbons and porous structure can accelerate electron and ion/gas transport during CO₂RR, respectively. This carbon electrocatalyst exhibits excellent selectivity toward CO₂ reduction to CH₄ with the faradaic efficiency of 68% at −0.50 V vs. RHE. As demonstrated by density functional theory, a proper adsorbed energy of *CO and *CH₂O are generated on the pyridinic N-B site resulting into high CH₄ selectivity. Therefore, this study provides a novel method to modulate active sites of carbon-based electrocatalyst to obtain high CH₄ selectivity.     

Encapsulation of a Porous Organic Cage into the Pores of a Metal–Organic Framework for Enhanced CO2 Separation

We present a facile approach to encapsulate functional porous organic cages (POCs) into a robust MOF by an incipient‐wetness impregnation method. Porous cucurbit[6]uril (CB6) cages with high CO₂ affinity were successfully encapsulated into the nanospace of Cr‐based MIL‐101 while retaining the crystal framework, morphology, and high stability of MIL‐101. The encapsulated CB6 amount is controllable. Importantly, as the CB6 molecule with intrinsic micropores is smaller than the inner mesopores of MIL‐101, more affinity sites for CO₂ are created in the resulting CB6@MIL‐101 composites, leading to enhanced CO₂ uptake capacity and CO₂/N₂, CO₂/CH₄ separation performance at low pressures. This POC@MOF encapsulation strategy provides a facile route to introduce functional POCs into stable MOFs for various potential applications.     

Encapsulation of an Ionic Metalloporphyrin into a Zeolite Imidazolate Framework in situ for CO2 Chemical Transformation via Host–Guest Synergistic Catalysis

It is a great challenge to rationally integrate multiple reactive sites into a composite material with confined nanospace, which can be applied as a nanoreactor to facilitate targeting catalytic reaction. In this work, an ionic metalloporphyrin has been encapsulated in situ into ZIF‐8 for a solvent‐free synthesis of cyclic carbonates from CO₂ and epoxides without any co‐catalyst under 1 atm CO₂.     

Graphene Oxide Membranes with Heterogeneous Nanodomains for Efficient CO2 Separations

Achieving high membrane performance in terms of gas permeance and carbon dioxide selectivity is an important target in carbon capture. Aiming to manipulate the channel affinity towards CO₂ to implement efficient separations, gas separation membranes containing CO₂‐philic and non‐CO₂‐philic nanodomains in the interlayer channels of graphene oxide (GO) were formed by intercalating poly(ethylene glycol) diamines (PEGDA). PEGDA reacts with epoxy groups on the GO surface, constructing CO₂‐philic nanodomains and rendering a high sorption capacity, whereas unreacted GO surfaces give non‐CO₂‐philic nanodomains, rendering low‐friction diffusion. Owing to the orderly stacking of nanochannels through cross‐linking and the heterogeneous nanodomains with moderate CO₂ affinity, a GO‐PEGDA500 membrane exhibits a high CO₂ permeance of 175.5 GPU and a CO₂/CH₄ selectivity of 69.5, which is the highest performance reported for dry‐state GO‐stacking membranes.     

Carbon Molecular Sieve Membrane Preparation by Economical Coating and Pyrolysis of Porous Polymer Hollow Fibers

Dip coating and pyrolysis processes are used to create multi‐layer asymmetric carbon molecular sieve (CMS) hollow fiber membranes with excellent gas separation properties. Coating of an economical engineered support with a high‐performance polyimide to create precursor fibers with a dense skin layer reduces material cost by 25‐fold compared to monolithic precursors or ceramic supports. CMS permeation results with CO₂/CH₄ (50:50) mixed gas feed show attractive CO₂/CH₄ selectivity of 58.8 and CO₂ permeance of 310 GPU at 35 °C.     

Optimizing the parameters of the steam-carbon dioxide conversion of methane by Gibbs energy minimization

The thermodynamic equilibrium for the steam-carbon dioxide conversion of methane was studied by Gibbs energy minimization. The degree of coke formation, the content of methane and carbon dioxide in the synthesis gas, and the synthesis gas H₂/CO ratio were plotted as functions of the molar ratios of CO₂/CH₄ and H₂O/CH₄ in the initial mixture at different temperatures and pressures. The regions of the optimum CH₄/CO₂/H₂O molar ratios for steam-carbon dioxide conversion were discovered, with no coke formation taking place in these regions. The optimized CH₄/CO₂/H₂O molar fractions characterized by the minimum content of methane and carbon dioxide in the synthesis gas were found for each region.     

Enhancing CO2 Separation Ability of a Metal–Organic Framework by Post‐Synthetic Ligand Exchange with Flexible Aliphatic Carboxylates

A series of porous metal–organic frameworks having flexible carboxylic acid pendants in their pores (UiO‐66‐ADn: n=4, 6, 8, and 10, where n denotes the number of carbons in a pendant) has been synthesized by post‐synthetic ligand exchange of terephthalate in UiO‐66 with a series of alkanedioic acids (HO₂C(CH₂)_n?2CO₂H). NMR, IR, PXRD, TEM, and mass spectral data have suggested that a terephthalate linker in UiO‐66 was substituted by two alkanedioate moieties, resulting in free carboxyl pendants in the pores. When post‐synthetically modified UiO‐66 was partially digested by adjusting the amount of added HF/sample, NMR spectra indicated that the ratio of alkanedioic acid/terephthalic acid was increased with smaller amounts of acid, implying that the ligand substitution proceeded from the outer layer of the particles. Gas sorption studies indicated that the surface areas and the pore volumes of all UiO‐66‐ADns were decreased compared to those of UiO‐66, and that the CO₂ adsorption capacities of UiO‐66‐ADn (n=4, 8) were similar to that of UiO‐66. In the case of UiO‐66‐AD6, the CO₂ uptake capacity was 34 % higher at 298 K and 58 % higher at 323 K compared to those of UiO‐66. It was elucidated by thermodynamic calculations that the introduction of flexible carboxyl pendants of appropriate length has two effects: 1) it increases the interaction enthalpy between the host framework and CO₂ molecules, and 2) it mitigates the entropy loss upon CO₂ adsorption due to the formation of multiple configurations for the interactions between carboxyl groups and CO₂ molecules. The ideal adsorption solution theory (IAST) selectivity for CO₂ adsorption over that of CH₄ was enhanced for all of the UiO‐66‐ADns compared to that of UiO‐66 at 298 K. In particular, UiO‐66‐AD6 showed the most strongly enhanced CO₂ uptake capacity and significantly increased selectivity for CO₂ adsorption over that of CH₄ at ambient temperature, suggesting that it is a promising material for sequestering CO₂ from landfill gas.     

Achieving Simultaneous CO2 and H2S Conversion via a Coupled Solar‐Driven Electrochemical Approach on Non‐Precious‐Metal Catalysts

Carbon dioxide (CO₂) and hydrogen sulfide (H₂S) are generally concomitant with methane (CH₄) in natural gas and traditionally deemed useless or even harmful. Developing strategies that can simultaneously convert both CO₂ and H₂S into value‐added products is attractive; however it has not received enough attention. A solar‐driven electrochemical process is demonstrated using graphene‐encapsulated zinc oxide catalyst for CO₂ reduction and graphene catalyst for H₂S oxidation mediated by EDTA‐Fe²⁺/EDTA‐Fe³⁺ redox couples. The as‐prepared solar‐driven electrochemical system can realize the simultaneous conversion of CO₂ and H₂S into carbon monoxide and elemental sulfur at near neutral conditions with high stability and selectivity. This conceptually provides an alternative avenue for the purification of natural gas with added economic and environmental benefits.     

Preparation and characterization of waste ion-exchange resin-based activated carbon for CO<Subscript>2</Subscript> capture

Waste ion-exchange resin was utilized as precursor to produce activated carbon by KOH chemical activation, on which the effects of different activation temperatures, activation times and impregnation ratios were studied in this paper. The CO₂ adsorption of the produced activated carbon was tested by TGA at 30 °C and environment pressure. Furthermore, the effects of preparation parameters on CO₂ adsorption were investigated. Experimental results show that the produced activated carbons are microporous carbons, which are suitable for CO₂ adsorption. The CO₂ adsorption capacity increases firstly and then decreases with the increase of activation temperature, activation time and impregnation rate. The maximum adsorption capacity is 81.24 mg/g under the condition of 30 °C and pure CO₂. The results also suggest that waste ion-exchange resin-based activated carbons possess great potential as adsorbents for post-combustion CO₂ capture.     

Adsorption of CO2 on nitrogen-enriched activated carbon and zeolite 13X

Adsorption may be a potentially attractive alternative to capturing CO₂ from stationary sources in the context of Carbon Capture and Sequestration (CCS) technologies. Activated carbon and zeolites are state-of-art adsorbents which may be used for CO₂ adsorption, however physisorption alone tends to be insignificant at high temperatures. In the present work, commercial adsorbents have been impregnated with monoethanolamine (MEA) and triethanolamine (TEA) in order to investigate the effect of the modified surface chemistry on CO₂ adsorption, especially above room temperature. Adsorption isotherms for CO₂, N₂ and CH₄ were measured in a gravimetrically system in the pressure range of UHV to 10 bar, at 298 and 348 K for activated carbon and zeolite 13X supports. The adsorbed concentration of CO₂ was significantly higher than those of CH₄ and N₂ for both adsorbents in the whole pressure range studied, zeolite 13X showing a remarkable affinity for CO₂ at very low pressures. However, at 348 K, the adsorbed concentration of CO₂ decreases significantly. The supports impregnated with concentrated amine solutions and dried in air suffered a detrimental effect on the textural properties, although CO₂ uptake became much less susceptible to temperature increase. Impregnations carried out with dilute solution followed by drying in inert atmosphere yielded materials with very similar textural characteristics as compared to the parent support. CO₂ isotherms in such materials showed a significant change with similar capacities at 348 K as compared to the original support at 298 K in the case of activated carbons. The impregnated zeolite showed a decrease in adsorbed phase concentration in low pressures for a given temperature, but the adsorbed amount also seemed to be less affected by temperature. These results are promising and indicate that CO₂ adsorption may be enhanced despite high process temperatures (e.g. 348 K), if convenient impregnation and drying methods are applied.     

Bioinspired Design of a Giant [Mn86] Nanocage-Based Metal-Organic Framework with Specific CO2 Binding Pockets for Highly Selective CO2 Separation

Adsorption-based removal of carbon dioxide (CO₂) from gas mixtures has demonstrated great potential for solving energy security and environmental sustainability challenges. However, due to similar physicochemical properties between CO₂ and other gases as well as the co-adsorption behavior, the selectivity of CO₂ is severely limited in currently reported CO₂-selective sorbents. To address the challenge, we create a bioinspired design strategy and report a robust, microporous metal–organic framework (MOF) with unprecedented [Mn₈₆] nanocages. Attributed to the existence of unique enzyme-like confined pockets, strong coordination interactions and dipole-dipole interactions are generated for CO₂ molecules, resulting in only CO₂ molecules fitting in the pocket while other gas molecules are prohibited. Thus, this MOF can selectively remove CO₂ from various gas mixtures and show record-high selectivities of CO₂/CH₄ and CO₂/N₂ mixtures. Highly efficient CO₂/C₂H₂, CO₂/CH₄, and CO₂/N₂ separations are achieved, as verified by experimental breakthrough tests. This work paves a new avenue for the fabrication of adsorbents with high CO₂ selectivity and provides important guidance for designing highly effective adsorbents for gas separation.     

Carbon Dioxide Destruction with Methane Reforming by a Novel Plasma-Catalytic Converter

A novel plasma-catalyst converter (NPCC) was engineered in applying the carbon capture utilization technology for the destruction of carbon dioxide (CO₂), which is a cause of global warming and is generated from the combustion of fossil fuels. The NPCC has an orifice-type baffle to improve an amount of gas feed with the higher CO₂ destruction for a stationary point sources application . To examine its ability for the CO₂ destruction, the performance analysis was conducted on the effects of methane additive, nozzle injection velocity, total gas feed, and catalyst type. The product gas from the NPCC was combustible components like CO, H₂, CH₄, THCs. The CO₂ destruction and the CH₄ conversion at a 1.29 CH₄/CO₂ ratio were 37 and 47 %, respectively, and the energy decomposition efficiency was 0.0036 L/min W. The nickel oxide catalyst among other catalysts showed the most effectiveness for the CO₂ destruction and CH₄ conversion at a lower temperature. The carbon-black produced without the catalytic bed has carbon nanoparticles with diverse shapes, such as spherical carbon particles and carbon nanotubes; and its high conductivity and specific surface area were suitable for special electronic materials, fuel cells, and nanocomponents.     

Rational Construction of an Exceptionally Stable MOF Catalyst with Metal-Adeninate Vertices toward CO2 Cycloaddition under Mild and Cocatalyst-Free Conditions

CO₂ is considered as the primary greenhouse gas, resulting in a series of serious environmental problems that affect people's life and health. Carbon capture and sequestration has been implemented as one of the most appealing pathways to control and use CO₂. Here, we rationally integrate various functional sites within the confined nanospace of a microporous metal–organic framework (MOF) material, which is constructed by mixed-ligand strategy based on metal-adeninate vertices. It not only exhibits excellent stability but also can efficiently transform CO₂ and epoxides to cyclic carbonates under mild and cocatalyst-free conditions. Additionally, this catalyst shows extraordinary recyclability for the CO₂ cycloaddition reaction.     

Confined Nanospace Pyrolysis for the Fabrication of Coaxial Fe3O4@C Hollow Particles with a Penetrated Mesochannel as a Superior Anode for Li‐Ion Batteries

In this study, a method is developed to fabricate Fe₃O₄@C particles with a coaxial and penetrated hollow mesochannel based on the concept of “confined nanospace pyrolysis”. The synthesis involves the production of a polydopamine coating followed by a silica coating on a rod‐shaped β‐FeOOH nanoparticle, and subsequent treatment by using confined nanospace pyrolysis and silica removal procedures. Typical coaxial hollow Fe₃O₄@C possesses a rice‐grain morphology and mesoporous structure with a large specific surface area, as well as a continuous and flexible carbon shell. Electrochemical tests reveal that the hollow Fe₃O₄@C with an open‐ended nanostructure delivers a high specific capacity (ca. 864 mA h g^?1 at 1 A g^?1), excellent rate capability with a capacity of about 582 mA h g^?1 at 2 A g^?1, and a high Coulombic efficiency (>97 %). The excellent electrochemical performance benefits from the hollow cavity with an inner diameter of 18 nm and a flexible carbon shell that can accommodate the volume change of the Fe₃O₄ during the lithium insertion/extraction processes as well as the large specific surface area and open inner cavity to facilitate the rapid diffusion of lithium ions from electrolyte to active material. This fabrication strategy can be used to generate a hollow or porous metal oxide structure for high‐performance Li‐ion batteries.