CuCl2-Activated Sustainable Microporous Carbons with Tailorable Multiscale Pores for Effective CO2 Capture

Porosity is the key factor in determining the CO2 capture capacity for porous carbon-based adsorbents, especially narrow micropores of less than 1.0 nm. Unfortunately, this desired feature is still a great challenge to tailor micropores by an effective, low-corrosion, and environmentally friendly activating agent. Herein, we reported a suitable dynamic porogen of CuCl2 to engineer microporous carbons rich in narrow micropores of <1.0 nm for solving the above problem. The porosity can be easily tuned by varying the concentration of the CuCl2 porogen. The resultant porous carbons exhibited a multiscale micropore size, high micropore volume, and suitable surface nitrogen doping content, especially high-proportioned ultromicropores of <0.7 nm. As adsorbents for capturing CO2, the obtained microporous carbons possess satisfactory CO2 uptake, moderate heat of CO2 adsorption, reasonable CO2/N2 selectivity, and easy regeneration. Our work proposes an alternative way to design porous carbon-based adsorbents for efficiently capturing CO2 from the postcombustion flue gases. More importantly, this work opens up an almost-zero cost and industrially friendly route to convert biowaste into high-added-value adsorbents for CO2 capture in an industrial practical application.

Enhanced CO2 Capture of Poly(amidoamine)-Modified Graphene Oxide Aerogels with the Addition of Carbon Nanotubes

Innovative dendrimer-modified graphene oxide (GO) aerogels are reported by employing generation 3.0 poly(amidoamine) (PAMAM) dendrimer and a combined synthesis approach based on the hydrothermal method and freeze-casting followed by lyophilization. The properties of modified aerogels were investigated with the dendrimer concentration and the addition of carbon nanotubes (CNTs) in varying ratios. Aerogel properties were evaluated via scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). The obtained results indicated a strong correlation of the N content with the PAMAM/CNT ratio, where optimum values were revealed. The CO₂ adsorption performance on the modified aerogels increased with the concentration of the dendrimer at an appropriate PAMAM/CNT ratio, reaching the value of 2.23 mmol g^-1 at PAMAM/CNT ratio of 0.6/0.12 (mg mL^-1). The reported results confirm that CNTs could be exploited to improve the functionalization/reduction degree in PAMAM-modified GO aerogels for CO₂ capture.

Experimental and modelling studies of carbon dioxide capture onto pristine, nitrogen-doped, and activated ordered mesoporous carbons

The search for suitable materials for carbon dioxide capture and storage has attracted the attention of the scientific community in view of the increased global CO₂ levels and its after-effects. Among the different materials under research, porous carbons and their doped analogues are extensively debated for their ability to store carbon dioxide at high pressures. The present paper examined high-pressure carbon dioxide storage studies of 1-D hexagonal and 3-D cubic ordered mesoporous pristine and N-doped carbons prepared using the nano-casting method. Excess carbon dioxide sorption isotherms were obtained using the volumetric technique and were fitted using the Toth model. Various parameters that influence CO₂ storage on metal-free ordered mesoporous carbons, such as the effect of pore size, pore dimension, pyrolysis temperature, the impact of nitrogen substitution, and the effect of ammonia activation are discussed. It was observed that the carbon dioxide storage capacity has an inverse relation to the total nitrogen doped, the amount of pyridinic nitrogen functionality, and the pyrolysis temperature, whereas the pore size seems to have a linear relationship. On the other hand, the presence of oxygen has a positive effect on the sorption capacity. Among the prepared ordered mesoporous carbons, the ammonia-treated one has shown the highest adsorption capacity of 37.8 mmol g^-1 at 34 bar and 0 °C.

Analysis of the Influence of Activated Carbons' Production Conditions on the Porous Structure Formation on the Basis of Carbon Dioxide Adsorption Isotherms

The results of a study of the impact of activation temperature and the mass ratio of the activator to the carbonised precursor on the porous structure of nitrogen-doped activated carbons obtained from lotus leaves by carbonisation and chemical activation with sodium amide (NaNH₂) are presented. The analyses were carried out via the new numerical clustering-based adsorption analysis, the Brunauer-Emmett-Teller, the Dubinin-Raduskevich, and the density functional theory methods applied to carbon dioxide adsorption isotherms. Carbon dioxide adsorption isotherms' analysis provided much more detailed and reliable information about the pore structure analysed. The analyses showed that the surface area of the analysed activated carbons is strongly heterogeneous, but the analysed activated carbons are characterised by a bimodal pore structure, i.e., peaks are clearly visible, first in the range of pore size from about 0.6 to 2.0 nm and second in the range from about 2.0 to 4.0 nm. This pore structure provides optimal adsorption performance of carbon dioxide molecules in the pore structure both for adsorption at atmospheric pressure, which requires the presence of narrow pores for the highest packing density, as well as for adsorption at higher pressures, which requires the presence of large micropores and small mesopores. However, there are no micropores smaller than 0.5 nm in the analysed activated carbons, which precludes their use for carbon dioxide adsorption for processes conducted at pressures less than 0.01 MPa.

Rational synthesis of microporous carbons for enhanced post-combustion CO2 capture via non-hydroxide activation of air carbonised biomass

This work explores the use of a less corrosive activating agent, potassium oxalate (PO), in combination with difficult to activate carbonaceous matter for the preparation of activated carbons. The design of the study allowed a fuller understanding of the workings of PO compared to hydroxide (KOH) activation, and also optimised the preparation of highly microporous carbons with exceptional CO₂ storage capacity under low pressure (≤1 bar) conditions at ambient temperature. The PO activated carbons have a surface area of up to 1760 m² g⁻¹ and are highly microporous with virtually all of the surface area arising from micropores. The porosity of the PO activated carbons can be readily tailored towards having pores of size 6–8 Å, which are highly suited for CO₂ storage at low pressure (i.e., post-combustion capture). At 25 °C, the PO activated carbons can store up to 1.8 and 5.0 mmol g⁻¹ of CO₂ at 0.15 bar and 1 bar, respectively. On the other hand, KOH activated carbons reach a higher surface area of up to 2700 m² g⁻¹, and store up to 1.0 and 4.0 mmol g⁻¹ of CO₂. This work demonstrates that PO may be used as a mild, less corrosive and less toxic activating agent for the rational and targeted synthesis of biomass-derived activated carbons with tailored porosity. The targeted synthesis may be aided by careful selection of the biomass starting material as guided by the O/C ratio of the biomass.

Rational combination of a mild activating agent (potassium oxalate) and air carbonised biomass, which is resistant to activation, yields highly microporous carbons with enhanced post-combustion CO₂ uptake.

A review on application of activated carbons for carbon dioxide capture: present performance, preparation, and surface modification for further improvement

The atmosphere security and regulation of climate change are being continuously highlighted as a pressing issue. The crisis of climate change owing to the anthropogenic carbon dioxide emission has led many governments at federal and provincial levels to promulgate policies to address this concern. Among them is regulating the carbon dioxide emission from major industrial sources such as power plants, petrochemical industries, cement plants, and other industries that depend on the combustion of fossil fuels for energy to operate. In view of this, various CO2 capture and sequestration technologies have been investigated and presented. From this review, adsorption of CO2 on porous solid materials has been gaining increasing attention due to its cost-effectiveness, ease of application, and comparably low energy demand. Despite the myriad of advanced materials such as zeolites, carbons-based, metal-organic frameworks, mesoporous silicas, and polymers being researched, research on activated carbons (ACs) continue to be in the mainstream. Therefore, this review is endeavored to elucidate the adsorption properties of CO2 on activated carbons derived from different sources. Selective adsorption based on pore size/shape and surface chemistry is investigated. Accordingly, the effect of surface modifications of the ACs with NH3, amines, and metal oxides on adsorption performance toward CO2 is evaluated. The adsorption performance of the activated carbons under humid conditions is also reviewed. Finally, activated carbon-based composite has been surveyed and recommended as a feasible strategy to improve AC adsorption properties toward CO2. The activated carbon surface in the graphical abstract is nitrogen rich modified using ammonia through thermal treatment. The values of CO2 emissions by sources are taken from (Yoro and Daramola 2020).

Facile synthesis and characterization of microporous-structured activated carbon from agro waste materials and its application for CO2 capture

Biomass-derived activated carbon was prepared from the agro waste materials, (wild sugarcane (WS) and saw dust (SD)) by chemical activation using phosphoric acid. The crystallinity, morphology, functional groups of the synthesized activated carbon were investigated. The effects of contact time (10-60 min), mass of adsorbent (0.05-0.2 g) and concentrations of CO2 (1 × 10-4 to 10 × 10-4 M) were analysed and the optimum adsorption conditions were found. Freundlich, Langmuir, Temkin, Dubinin-Radushkevich and Sips isotherm were used to analyse the adsorption data. The adsorption process was fitted with the Freundlich model. Adsorption capacity of agro waste-based sorbent was 5.225 × 10-3 mol/g. Thermodynamic parameters, such as ΔH0, ΔG0, ΔS0 , were calculated and it was found that the present system was a spontaneous process. From the kinetic studies, it was inferred that the Pseudo-second-order kinetics describes the kinetics of CO2 on AC-WSSD with an equilibrium point attained at 50 minutes with a high R2 value of 0.9602. The Brunauer Emmett Teller (BET) surface area of 1220 m2/g and an iodine value of 1360 m2/g were better indications for adsorption process. The interaction between CO2 and functional groups on the surface of the activated carbon was confirmed by FTIR. Desorption studies were carried out for three cycles with an efficiency of 93.2%.

Advances in Post-Combustion CO2 Capture by Physical Adsorption: From Materials Innovation to Separation Practice

The atmospheric CO₂ concentration continues a rapid increase to its current record high value of 416 ppm for the time being. It calls for advanced CO₂ capture technologies. One of the attractive technologies is physical adsorption-based separation, which shows easy regeneration and high cycle stability, and thus reduced energy penalties and cost. The extensive research on this topic is evidenced by the growing body of scientific and technical literature. The progress spans from the innovation of novel porous adsorbents to practical separation practices. Major CO₂ capture materials include the most widely used industrially relevant porous carbons, zeolites, activated alumina, mesoporous silica, and the newly emerging metal-organic frameworks (MOFs) and covalent-organic framework (COFs). The key intrinsic properties such as pore structure, surface chemistry, preferable adsorption sites, and other structural features that would affect CO₂ capture capacity, selectivity, and recyclability are first discussed. The industrial relevant variables such as particle size of adsorbents, the mechanical strength, adsorption heat management, and other technological advances are equally important, even more crucial when scaling up from bench and pilot-scale to demonstration and commercial scale. Therefore, we aim to bring a full picture of the adsorption-based CO₂ separation technologies, from adsorbent design, intrinsic property evaluation to performance assessment not only under ideal equilibrium conditions but also in realistic pressure swing adsorption processes.

CO2 adsorption mechanisms on MOFs: a case study of open metal sites, ultra-microporosity and flexible framework

In this review the CO₂ adsorption mechanisms of MOF-74-Mg, HKUST-1, SIFSIX-3-M, and ZIF-8 are explored, highlighting their preferential adsorption sites, CO₂–MOF complex configuration, adsorption dynamics, bonding angle, and water stability.

Structural Deterioration of Well-Faceted MOFs upon H2S Exposure and Its Effect in the Adsorption Performance

The structural deterioration of archetypical, well-faceted metal-organic frameworks (MOFs) has been evaluated upon exposure to an acidic environment (H₂S). Experimental results show that the structural damage highly depends on the nature of the hybrid network (e.g., softness of the metal ions, hydrophilic properties, among others) and the crystallographic orientation of the exposed facets. Microscopy images show that HKUST-1 with well-defined octahedral (111) facets is completely deteriorated, ZIF-8 with preferentially exposed (110) facets exhibits a large external deterioration with the development of holes or cavities in the mesoporous range, whereas UiO-66-NH₂ with (111) exposed facets, and PCN-250 with (100) facets does not reflect any sign of surface damage. Despite the selectivity in the external deterioration, X-ray diffraction and gas adsorption measurements confirm that indeed all MOFs suffer an important internal deterioration, these effects being more severe for MOFs based on softer cations (e.g., Cu-based HKUST-1 and Fe-based PCN-250). These structural changes have inevitable important effects in the final adsorption performance for CO₂ and CH₄ at low and high pressures.

Tailoring Low-Cost Granular Activated Carbons Intended for CO2 Adsorption

Physical adsorption on activated carbons has shown to be a very attractive methodology for CO₂ separation from flue gas streams and biogas. In this context, the goal of this work was to prepare granular activated carbons intended for CO₂ adsorption from an abundant and low-cost biomass residue (coconut shell) by using practical and cost-effective procedures. By the first time, parameters involved in chemical activation with dehydrating agents (H₃PO₄ or ZnCl₂) and/or physical activation with CO₂ were systematically screened in depth in order to obtain materials with improved performance for CO₂ adsorption on a volume basis. Compared with the commonly used mass basis, the data expressed on a volume basis are very important for industrial applications because they permit to estimate the efficiency of a fixed bed adsorption column. The work permitted to prepare granular activated carbons with a blend of relatively high gravimetric CO₂ uptake and bulk density, so that high volumetric CO₂ uptakes were attained. The highest values were 2.67 and 1.17 mmol/cm³ for CO₂ pressures of 1.0 and 0.15 bar, respectively. It is remarkable that the obtained results were similar to those reported by other authors for carbons chemically activated with KOH, the activation methodology that has been widely claimed as the one that produce ACs with the best performances for CO₂ adsorption, but which involves severe restrictions. Therefore, the present work can be considered a very important step in paving the way toward making CO₂ adsorption an each time more interesting technology to reduce the emissions of anthropogenic greenhouse gases.

Metal-Organic Complexes@Melamine Foam Template Strategy to Prepare Three-Dimensional Porous Carbon with Hollow Spheres Structures for Efficient Organic Vapor and Small Molecule Gas Adsorption

Three-dimensional (3D) porous carbon materials have received substantial attention owing to their unique structural features. However, the synthesis of 3D porous carbon, especially 3D porous carbon with hollow spheres structures at the connection points, still pose challenges. Herein, we first develop a metal-organic complexes@melamine foam (MOC@MF) template strategy, by using hot-pressing and carbonization method to synthesize 3D porous carbon with hollow spheres structures (denoted as NOPCs). The formation mechanism of NOPCs can be attributed to the difference in Laplace pressure and surface energy gradient between the carbonized MOC and carbonized MF. These rare 3D porous carbons exhibit high BET surface area (2453.8 m² g^-1), N contents (10.5%), and O contents (16.3%). Moreover, NOPCs show significant amounts of toluene and methanol at room temperature, reaching as high as 1360 and 1140 mg g^-1. The adsorption amounts of SO₂ and CO₂ for NOPCs are up to 93.1 and 445 mg g^-1. Theoretical calculation indicates surfaces of porous carbon with N and O coexistence could strongly enhance adsorption with high adsorption energy of -65.83 kJ mol g^-1.

An overview on trace CO2 removal by advanced physisorbent materials

This review paper focuses on various gas processing technologies and materials that efficiently capture trace levels of carbon dioxide (CO₂). Fundamental separation mechanisms such as absorption, adsorption, and distillation technology are presented. Liquid amine-based carbon capture (C-capture) technologies have been in existence for over half a century, however, liquid amine capture relies upon chemical reactions and is energy-intensive. Liquid amines are thus not economically viable for broad deployment and offer little room for innovation. Innovative C-capture technologies must improve both the environmental footprint and cost-effectiveness. As a promising alternative, physisorbents have many advantages including considerably lower regeneration energy. Generally, existing classes of physisorbent materials, such as metal-organic frameworks (MOFs) and zeolites are selective toward C-capture. However, their selectivity is currently not high enough to remove trace levels (e.g., ~1%) of CO₂ from various natural gas process streams. This review summarizes the current advancements in physisorbent materials for CO₂ capture. Here, key performance parameters needed to select the most suitable candidate are highlighted. Furthermore, this review discusses the scope for the development of better performing CO₂ selective physisorbents from both environmental and economic perspectives. In addition, hybrid ultra microporous materials (HUMs), characterized mainly by ultra-micro pores (<0.7 nm), are discussed in reference to C-capture. Various characteristics of HUMs result in high selectivity and applicability in difficult separations such as the gas sweetening and C-capture from complex humid mixed gas streams.

Synthesis of micro–mesoporous CPO-27-Mg@KIT-6 composites and their test in CO2 adsorption

Novel composites were synthesised through a fusion between CPO-27-Mg framework and mesoporous silica KIT-6 and tested in the CO₂ adsorption.

Activated Carbon in the Third Dimension-3D Printing of a Tuned Porous Carbon

A method for obtaining hierarchically structured porous carbons, employing 3D printing to control the structure down to the lower µm scale, is presented. To successfully 3D print a polymer precursor and transfer it to a highly stable and structurally conformal carbon material, stereolithography 3D printing and photoinduced copolymerization of pentaerythritol tetraacrylate and divinylbenzene are employed. Mechanically stable structures result and a resolution of ≈15 µm is demonstrated. This approach can be combined with liquid porogen templating to control the amount and size (up to ≈100 nm) of transport pores in the final carbonaceous material. Additional CO2 activation enables high surface area materials (up to 2200 m2 g-1) that show the 3D printing controlled µm structure and nm sized transport pores. This unique flexibility holds promise for the identification of optimal carbonaceous structures for energy application, catalysis, and adsorption.

Enhanced CO2 Adsorption on Nitrogen-Doped Carbon Materials by Salt and Base Co-Activation Method

Nitrogen-doped carbon materials with enhanced CO₂ adsorption were prepared by the salt and base co-activation method. First, resorcinol-formaldehyde resin was synthesized with a certain salt as an additive and used as a precursor. Next, the resulting precursor was mixed with KOH and subsequently carbonized under ammonia flow to finally obtain the nitrogen-doped carbon materials. A series of samples, with and without the addition of different salts, were prepared, characterized by XRD (X-ray powder diffraction), elemental analysis, BET (N₂-adsorption-desorption analysis), XPS (X-ray photoelectron spectroscopy) and SEM (Scanning electron microscopy) and tested for CO₂ adsorption. The results showed that the salt and base co-activation method has a remarkable enhancing effect on the CO₂ capture capacity. The combination of KCl and KOH was proved to be the best combination, and 167.15 mg CO₂ could be adsorbed with 1 g nitrogen-doped carbon at 30 °C under 1 atm pressure. The materials characterizations revealed that the introduction of the base and salt could greatly increase the content of doped nitrogen, the surface area and the amount of formed micropore, which led to enhanced CO₂ absorption of the carbon materials.

Stability of amine-functionalized CO2 adsorbents: a multifaceted puzzle

This review focuses on important stability issues facing amine-functionalized CO2 adsorbents, including amine-grafted and amine-impregnated silicas, zeolites, metal-organic frameworks and carbons. During the past couple of decades, major advances were achieved in understanding and improving the performance of such materials, particularly in terms of CO2 adsorptive properties such as adsorption capacity, selectivity and kinetics. Nonetheless, to pave the way toward commercialization of adsorption-based CO2 capture technologies, in addition to other attributes, adsorbent materials should be stable over many thousands of adsorption-desorption cycles. Adsorbent stability, which is of utmost importance as it determines adsorbent lifetime and operational costs of CO2 capture, is a multifaceted issue involving thermal, hydrothermal, and chemical stability. Here we discuss the impact of the adsorbent physical and chemical properties, the feed gas composition and characteristics, and the adsorption-desorption operational parameters on the long-term stability of amine-functionalized CO2 adsorbents. We also review important insights associated with the underlying deactivation pathways of the adsorbents upon exposure to high temperature, oxygen, dry CO2, sulfur-containing compounds, nitrogen oxides, oxygen and steam. Finally, specific recommendations are provided to address outstanding stability issues.

A photoluminescent indium-organic framework with discrete cages and one-dimensional channels for gas adsorption

We have successfully obtained, for the first time, a new heterometallic indium-organic framework (InOF-14) with a functional and luminescent Eu(iii) component. Based on the mutually competitive [In(CO2)4] and [Eu2(CO2)4(H2O)4] units, this microporous structure possesses discrete nano-cages and one-dimensional channels for gas adsorption, and simultaneously exhibits excellent luminescence properties.

Individual Nanoporous Carbon Spheres with High Nitrogen Content from Polyacrylonitrile Nanoparticles with Sacrificial Protective Layers

Functional nanoporous carbon spheres (NPC-S) are important for applications ranging from adsorption, catalysis, separation to energy storage, and biomedicine. The development of effective NPC-S materials has been hindered by the fusion of particles during the pyrolytic process that results in agglomerated materials with reduced activity. Herein, we present a process that enables the scalable synthesis of dispersed NPC-S materials by coating sacrificial protective layers around polyacrylonitrile nanoparticles (PAN NPs) to prevent interparticle cross-linking during carbonization. In a first step, PAN NPs are synthesized using miniemulsion polymerization, followed by grafting of 3-(triethoxysilyl)propyl methacrylate (TESPMA) to form well-defined core-shell structured PAN@PTESPMA nanospheres. The cross-linked PTESPMA brush layer suppresses cross-linking reactions during carbonization. Uniform NPC-S exhibiting diameters of ∼100 nm, with relatively high accessible surface area (∼424 m²/g), and high nitrogen content (14.8 wt %) was obtained. When compared to a regular nanoporous carbon monolith (NPC-M), the nitrogen-doped NPC-S demonstrated better performance for CO₂ capture with a higher CO₂/N₂ selectivity, an increased efficiency in catalytic oxygen reduction reactions, as well as improved electrochemical capacitive behavior. This miniemulsion polymerization-based strategy for the preparation of functional PAN NPs provides a new, facile approach to prepare high-performance porous carbon spheres for diverse applications.

Porous Organic Polymers for Post-Combustion Carbon Capture

One of the most pressing environmental concerns of our age is the escalating level of atmospheric CO₂ . Intensive efforts have been made to investigate advanced porous materials, especially porous organic polymers (POPs), as one type of the most promising candidates for carbon capture due to their extremely high porosity, structural diversity, and physicochemical stability. This review provides a critical and in-depth analysis of recent POP research as it pertains to carbon capture. The definitions and terminologies commonly used to evaluate the performance of POPs for carbon capture, including CO₂ capacity, enthalpy, selectivity, and regeneration strategies, are summarized. A detailed correlation study between the structural and chemical features of POPs and their adsorption capacities is discussed, mainly focusing on the physical interactions and chemical reactions. Finally, a concise outlook for utilizing POPs for carbon capture is discussed, noting areas in which further work is needed to develop the next-generation POPs for practical applications.

Computational evaluation of aluminophosphate zeotypes for CO2/N2 separation

Zeolites and structurally related materials (zeotypes) have received considerable attention as potential adsorbents for selective carbon dioxide adsorption. Within this group, zeotypes with aluminophosphate composition (AlPOs) could be an interesting alternative to the more frequently studied aluminosilicate zeolites. So far, however, only a few AlPOs have been characterised experimentally in terms of their CO₂ adsorption properties. In this study, force-field based grand-canonical Monte Carlo (GCMC) simulations were used to evaluate the potential of AlPOs for CO₂/N₂ separation, a binary mixture that constitutes a suitable model system for the removal of carbon dioxide from flue gases. A total of 51 frameworks were considered, all of which have been reported either as pure AlPOs or as heteroatom-containing AlPO derivatives. Prior to the GCMC simulations, all structures were optimised using dispersion-corrected density-functional theory calculations. The potential of these 51 systems for CO₂/N₂ separation was assessed in preliminary calculations (Henry constants and CO₂ uptake at selected pressures). On the basis of these calculations, 21 AlPOs of particular interest were selected, for which 15 : 85 CO₂/N₂ mixture adsorption isotherms were calculated up to 10 bar. For adsorption-based separations using an adsorption pressure of 1 bar (vacuum-swing adsorption), AlPOs with GIS, ATN, ATT, and SIV topologies were predicted to be most attractive, as they combine high CO₂/N₂ selectivities (75 to 140) and reasonable CO₂ working capacities (1 to 1.7 mmol g^-1). Under pressure-swing adsorption conditions, there is a tradeoff between selectivity and working capacity: while highly selective AlPOs like GIS reach only moderate working capacities, the frameworks with the highest working capacities above 2 mmol g^-1, AFY, KFI, and SAV, have lower selectivities between 25 and 35. To gain atomic-level insights into the host-guest interactions, interaction energy maps were computed for selected AlPOs. The computational assessment presented here can guide future experimental efforts in the development and optimisation of AlPO-based adsorbents for selective CO₂ adsorption.

Cooperative CO2 adsorption promotes high CO2 adsorption density over wide optimal nanopore range

Separation of CO2 based on adsorption, absorption, and membrane techniques is a crucial technology necessary to address current global warming issues. Porous media are essential for all these approaches and understanding the nature of the porous structure is important for achieving highly efficient CO2 adsorption. Porous carbon is considered to be a suitable porous media for investigating the fundamental mechanisms of CO2 adsorption, because of its simple morphology and its availability in a wide range of well-defined pore sizes. In this study, we investigated the dependence of CO2 adsorption on pore structures such as pore size, volume, and specific surface area. We also studied slit-shaped and cylindrical pore morphologies based on activated carbon fibers of 0.6–1.7 nm and carbon nanotubes of 1–5 nm, respectively, with relatively uniform structures. Porous media with larger specific surface areas gave higher CO2 adsorption densities than those of media having larger pore volumes. Narrower pores gave higher adsorption densities because of deep adsorption potential wells. However, at a higher pressure CO2 adsorption densities increased again in nanopores including micropores and small mesopores. The optimal pore size ranges of CO2 adsorption in the slit-shaped and cylindrical carbon pores were 0.4–1.2 and 1.0–2.0 nm, respectively, although a high adsorption density was only expected for the narrow carbon nanopores from adsorption potentials. The wider nanopore ranges than expected nanopore ranges are reasonable when considering intermolecular interactions in addition to CO2–carbon pore interactions. Therefore, cooperative adsorption among CO2 in relatively narrow nanopores can allow for high density and high capacity adsorption.

Adsorptive Water Removal from Dichloromethane and Vapor-Phase Regeneration of a Molecular Sieve 3A Packed Bed

The drying of dichloromethane with a molecular sieve 3A packed bed process is modeled and experimentally verified. In the process, the dichloromethane is dried in the liquid phase and the adsorbent is regenerated by water desorption with dried dichloromethane product in the vapor phase. Adsorption equilibrium experiments show that dichloromethane does not compete with water adsorption, because of size exclusion; the pure water vapor isotherm from literature provides an accurate representation of the experiments. The breakthrough curves are adequately described by a mathematical model that includes external mass transfer, pore diffusion, and surface diffusion. During the desorption step, the main heat transfer mechanism is the condensation of the superheated dichloromethane vapor. The regeneration time is shortened significantly by external bed heating. Cyclic steady-state experiments demonstrate the feasibility of this novel, zero-emission drying process.

Salt Templating with Pore Padding: Hierarchical Pore Tailoring towards Functionalised Porous Carbons

We propose a new synthetic route towards nanoporous functional carbon materials based on salt templating with pore-padding approach (STPP). STPP relies on the use of a pore-padding agent that undergoes an initial polymerisation/ condensation process prior to the formation of a solid carbon framework. The pore-padding agent allows tailoring hierarchically the pore-size distribution and controlling the amount of heteroatom (nitrogen in this case) functionalities as well as the type of nitrogen (graphitic, pyridinic, oxides of nitrogen) incorporated within the carbon framework in a single-step-process. Our newly developed STPP method offers a unique pathway and new design principle to create simultaneously high surface area, microporosity, functionality and pore hierarchy. The functional carbon materials produced by STPP showed a remarkable CO₂ /N₂ selectivity. At 273 K, a carbon with only micropores offered an exceptionally high CO₂ adsorption capacity whereas a carbon with only mesopores showed promising CO₂ -philicity with high CO₂ /N₂ selectivity in the range of 46-60 %, making them excellent candidates for CO₂ capture from flue gas or for CO₂ storage.

Applications of hierarchically structured porous materials from energy storage and conversion, catalysis, photocatalysis, adsorption, separation, and sensing to biomedicine

A comprehensive review of the recent progress in the applications of hierarchically structured porous materials is given.

Gas storage and separation in a water-stable [CuI5BTT3]4− anion framework comprising a giant multi-prismatic nanoscale cage

A water-stable Cu(i)-based metal–organic framework, featuring a giant multi-prismatic nanoscale cage and high CO₂/N₂ and CO₂/H₂ sorption selectivities, was constructed using the nitrogen-rich ligand of 1,3,5-tris(2H-tetrazol-5-yl)benzene (H₃BTT).

Superior CO2 adsorption from waste coffee ground derived carbons

Utilising waste from spent coffee grounds KOH activated highly microporous carbons with surface areas of 2785 m² g⁻¹ and micropore volumes of 0.793 cm³ g⁻¹ were synthesised that are capable of uptake capacities near 3 mmol g⁻¹ at 50 °C and 1 bar.

Triethylenetetramine-Modified P123-Occluded Zr-SBA-15 Molecular Sieve for CO2 Adsorption

A pluronic 123 (P123)-occluded mesoporous molecular sieve Zr-SBA-15, Zr-SBA(P) was modified with triethylenetetramine (TETA) and tested for CO2 adsorption. The synthesized materials were characterized by powder X-ray diffraction, N2 adsorption–desorption, dispersive spectroscopy, thermogravimetric analysis, temperature-programmer desorption of CO2, and Fourier transform infrared spectroscopy. The results of CO2 adsorption show that the TETA and P123 species have positive effects on the CO2 adsorption capacity of the adsorbent, and the performance of the as-prepared adsorbent in a stream of low CO2 concentration is excellent. At 50 wt-% TETA loading, Zr-SBA(P) has a maximum capacity of 4.27 mmol g–1 in a stream of 5 % CO2 at 50°C, ~33.5 % higher than the adsorbent prepared in the absence of P123. In addition, the adsorbent is superior in reusability. It is envisaged that the adsorbent will find wide application in CO2 capture.