Low-concentration CO2 Capture Research Articles

Carbon-based materials for low concentration CO2 capture and electrocatalytic reduction

The gradual increase in carbon dioxide (CO2) concentration in the atmosphere has been recognized as a significant problem for humankind. CO2 flue gas is one of the most apparent contributing sources of emissions. CO2 capture and conversion are environmental-friendly and efficient ways to reduce atmospheric carbon dioxide emissions from flue gases. Considering the traditional expensive gas purification process of low-concentration CO2, the low-cost capturing and electrocatalytic CO2 reduction (ECR) at low concentration by newly-developed carbon-based materials provide an attractive approach to convert low-concentration CO2 in flue gas into high-value fuels and chemicals. Developing and integrating carbon-based capturing and catalytic materials with an understanding of the mechanism has a promising future and will promote this technology toward practical application. This review describes recent progress in the design, preparation, and structural characterization of existing carbon-based materials for the capture and catalysis of low-concentration CO2. The crucial factors of capturing and catalysis performance of all the carbon-based materials are also summarized. Furthermore, the review identifies existing research problems and challenges, and outlines future research directions. We also discuss the prospects for the industrialization of low-concentration CO2 capture and ECR. The remaining technological challenges and future directions for enhancing and applying of carbon-based materials for CO2 capture and electrocatalytic reduction are highlighted.

Na-doped Li4SiO4 as an efficient sorbent for low-concentration CO2 capture at high temperature: Superior adsorption and rapid kinetics mechanism

Lithium silicate (Li4SiO4) sorbent has garnered attention in CO2 capture due to its high theoretical adsorption capacity and fast kinetics. However, its adsorption capacity and kinetics were hindered by low CO2 concentration. Improving adsorption performance of Li4SiO4 at low CO2 concentration has become the key to industrial application. In this work, high-activity Na-doped Li4SiO4 with controllable active substance Li3NaSiO4 was achieved. The influences of raw materials ratios on the CO2 adsorption performance were systematically investigated. When RLi/Si=4.05:1 and RNa/Si=0.15:1, the sample exhibited the highest adsorption capacity of 32.28 wt% with an equilibrium time of 29 min, and a superior stable capacity of 31.09 wt% in 15 cycles. Importantly, the double exponential fitting revealed that LiNaCO3 accelerated the ion diffusion rate and real-time adsorption processes showed Li3NaSiO4 expedited surface chemical reaction rate. Based on these, a novel Na2CO3 eutectic doping mechanism was proposed. The active substance Li3NaSiO4, generated through Na doping, along with its product formed from the reaction with CO2, molten LiNaCO3, acted synergistically to improve adsorption performance by accelerating surface chemical reaction rate and ion diffusion rate. Compared with other doped Li4SiO4, the sorbent prepared in this work demonstrated competitive adsorption performance, providing theoretical and technical support for the large-scale production of high-activity Li4SiO4.

Dynamic breakthrough performance of low concentration CO2 adsorption in fixed-bed column with porous amino acid ionic liquid composites

Low concentration carbon dioxide (CO2) capture from air or confined spaces currently faces significant challenges, such as relatively poor dynamic adsorption breakthrough performance and cyclic stability. In our previous work, functionalized ionic liquid (IL) tetraethylammonium glycine ([N2222][Gly]) and porous molecular sieve (SBA-15) were combined to synthesize porous amino acid IL composite 60 wt% [N2222][Gly]@SBA-15 with microporous and ultra-microporous structures, which provide a new pathway for low concentration CO2 capture. In order to further obtain the dynamic CO2 adsorption breakthrough performance of this material under simulated actual working conditions, the effects of temperatures, relative humidity (RH) and CO2 concentrations on CO2 adsorption and desorption breakthrough performance of 60 wt% [N2222][Gly]@SBA-15 in a fixed-bed column were systematically studied in this work. The results indicated that CO2 adsorption capacity is up to 1.81 mmolCO2/g-adsorbent at 298.15 K, 1 bar and 0 % RH under 1 vol% CO2-containing gas mixture balanced with N2 and reaches 2.44 mmolCO2/g-adsorbent at 15 % RH due to the mechanism change of CO2 reaction with primary amine from 2: 1 under dry gas to 1: 1 stoichiometry in the presence of moisture. Moreover, the adsorbent maintains good cyclic adsorption-desorption performance. Further, CO2 adsorption breakthrough behaviors were well fitted by Avrami kinetic model, and the CO2 adsorption rate of 60 wt% [N2222][Gly]@SBA-15 was controlled by intra-particle diffusion. This work implied that IL-modified adsorbents have great potentials for low concentration CO2 capture applications.

Adsorption of high-temperature CO2 by Ca2+/Na+-doped lithium orthosilicate: characterization, kinetics, and recycle.

High-temperature solid adsorbent Li4SiO4 has received broad attention due to its high theoretical adsorption capacity, high regeneration capacity, and wide range of raw materials for preparation. In this paper, a Li4SiO4 adsorbent was prepared by MCM-48 as the silica precursor and modified by doping with metal ions (Ca2+ and Na+) for high-temperature capture of low-concentration CO2. The results showed that the surface of the Ca-doped (or Na-doped) Li4SiO4 adsorbent developed some particles that are primarily composed by Li2CaSiO4 (or Li3NaSiO4). Furthermore, the grains of the adsorbents became finer, effectively increasing the specific surface area and enhancing adsorption performance. Under 15 vol% CO2, the maximum CO2 adsorption was 25.63 wt% and 32.86 wt% when the Ca2+ doping amount was 0.06 and the Na+ doping amount was 0.12, respectively. These values were both higher than the adsorption capacity before the metal ion doping. After 10 adsorption/desorption cycles, the adsorption capacity of Na-doped Li4SiO4 increased by 9.68 wt%, while that of Ca-doped Li4SiO4 decreased by 7.98 wt%. This difference could be attributed to the easy sintering of the Ca-containing adsorbent. Furthermore, a biexponential model was used to fit the CO2 adsorption curve of the adsorbent in order to study the adsorption kinetics. Compared to the conventional Li4SiO4, the Ca/Na-doped adsorbent offers several advantages, such as a high CO2 adsorption capacity and stable cycling ability.

Direct capture of low-concentration CO2 and selective hydrogenation to CH4 over Al2O3-supported Ni–La dual functional materials

La-modified Al2O3-supported Ni nanoparticles were developed as effective dual functional materials for direct capture of low-concentration CO2 and selective hydrogenation to CH4 under mild reaction conditions.

Ultrastable bifunctional multi-stage active metal catalysts for low concentration CO2 capture and in-situ conversion

Integrating CO2 capture and in-situ conversion is a promising means of processing low concentration CO2 in flue gas. The development of a low cost, highly stable catalyst to reduce the running cost is key to the development of this technology. The ultrastable bifunctional multi-stage active metal catalysts (Ca12Al14O33-y (Ca2Fe2O5)-CoxCaO) were synthesized by the solid phase synthesis method with low cost industrial powder raw materials. The catalyst was stabilized with calcium aluminate (Ca12Al14O33) and calcium ferrite (Ca2Fe2O5) as a substrate structural framework for CaO and enhanced the dispersion of CaO. It not only solved the problem of CaO deactivation due to sintering, pore collapse, and agglomeration in the continuous high-temperature reaction, but also showed excellent catalytic performance for reverse-water–gas-shift (RWGS) reaction. On the basis of calcium-looping and RWGS reaction, the high temperature CO2 capture and in-situ conversion process is realized in the same fixed-bed reactor for processing simulated flue gas with 16.7 vol% CO2. The results showed that at the optimum operating temperature of 610 °C, the catalyst still maintains a stable CO2 capture capacity, over 98% CO2 conversion rate and close to 100% CO selectivity after 100 cycles. The multi-stage active metal structure catalysts provided a unique construction idea for designing ultrastable catalysts for low concentration CO2 capture and in-situ conversion with great potential for industrial application.

High-performance CO2 Capture from Air by Harnessing the Power of CaO- and Superbase Ionic Liquid-Engineered Sorbents.

Direct air capture (DAC) of CO2 by solid porous materials represents an attractive "negative emission" technology. However, state-of-the-art sorbents based on supported amines still suffer from unsolved high energy consumption and stability issues. Herein, taking clues from the CO2 interaction with superbase-derived ionic liquids (SILs), high-performance and tunable sorbents in DAC of CO2 was developed by harnessing the power of CaO- and SIL-engineered sorbents. Deploying mesoporous silica as the substrate, a thin CaO layer was first introduced to consume the surface-OH groups, and then active sites with different basicities (e.g., triazolate and imidazolate) were introduced as a uniformly distributed thin layer. The as-obtained sorbents displayed high CO2 uptake capacity via volumetric (at 0.4 mbar) and breakthrough test (400 ppm CO2 source), rapid interaction kinetics, facile CO2 releasing, and stable sorption/desorption cycles. Operando Diffuse Reflectance Infrared Fourier Transformation Spectroscopy (DRIFTS) analysis under simulated air atmosphere and solid-state Nuclear Magnetic Resonance (NMR) under 13CO2 atmosphere demonstrated the critical roles of the SIL species in low-concentration CO2 capture.The fundamental insights obtained in this work provide guidance on the development of high-performance sorbents in DAC of CO2 by leveraging the combined advantages of porous solid scaffolds and the unique features of CO2-philic ILs.

Effect of Functional Groups on Low-Concentration Carbon Dioxide Capture in UiO-66-Type Metal–Organic Frameworks

The selective capture of low-concentration CO2 from air or confined spaces remains a great challenge. In this study, various functional groups were introduced into UiO-66 to generate functionalized derivatives (UiO-66-R, R = NO2, NH2, OH, and CH3), aiming at significantly enhancing CO2 adsorption and separation efficiency. More significantly, UiO-66-NO2 and UiO-66-NH2 with high polarity exhibit exceptional CO2 affinity and optimal separation characteristics in mixed CO2/O2/N2 (1:21:78). In addition, the impressive stability of UiO-66-NO2 and UiO-66-NH2 endows them with excellent recycling stability. The effective adsorption and separation performances demonstrated by these two functional materials suggest their potential as promising physical adsorbents for capturing low-concentration CO2.

Low-concentration CO2 capture system with liquid-like adsorbent based on monoethanolamine for low energy consumption

Direct air capture (DAC) of atmospheric CO2 is becoming ever more important for a carbon neutral society. To achieve this, it is critical to reduce the energy consumption of DAC systems. In this work, as a solution, a liquid-like adsorbent (LLA) is used as an adsorbent for DAC of low-concentration CO2. We improve the performance of LLA with monoethanolamine (MEA), and named it as LLA-M to efficiently capture atmospheric CO2 and reduce energy consumption at DAC environment. The effective dispersion of MEA in the LLA promotes CO2 capture by overcoming their low thermal stability. When 40 wt% MEA is added, the highest performance is achieved along with a CO2 capture capacity of 2.50 mmol g−1 in 100% CO2 atmosphere and 1.01 mmol g−1 in low CO2 concentration atmosphere. The loss and deterioration of MEA is suppressed by the LLA and therefore the performance is stably maintained while repeating the CO2 capture/regeneration cycles. Consequently, the CO2 capture capacity is improved by 29.9% compared with when using only MEA. More importantly, the results indicate a record CO2 capture energy consumption of 0.89 GJ tCO2−1 at 100% CO2 condition and 2.13 GJ tCO2−1 at 400 ppm CO2 condition. Furthermore, the LLA-M can be recycled below 120 °C which makes it possible to reduce energy consumption by exploiting renewable energies such as solar heat. This study offers a promising low-carbon route for efficient atmospheric CO2 capture using an LLA incorporated with MEA.

Controlled alkali etching of MOFs with secondary building units for low-concentration CO2 capture.

Low-concentration CO2 capture is particularly challenging because it requires highly selective adsorbents that can effectively capture CO2 from gas mixtures containing other components such as nitrogen and water vapor. In this study, we have successfully developed a series of controlled alkali-etched MOF-808-X (where X ranges from 0.04 to 0.10), the FT-IR and XPS characterizations revealed the presence of hydroxyl groups (-OH) on the zirconium clusters. Low-concentration CO2 capture experiments demonstrated improved CO2 capture performance of the MOF-808-X series compared to the pristine MOF-808 under dry conditions (400 ppm CO2). Among them, MOF-808-0.07 with abundant Zr-OH sites showed the highest CO2 capture capacity of 0.21 mmol g-1 under dry conditions, which is 70 times higher than that of pristine MOF-808. Additionally, MOF-808-0.07 exhibited fast adsorption kinetics, stable CO2 capture under humid air conditions (with a relative humidity of 30%), and stable regeneration even after 50 cycles of adsorption and desorption. In situ DRIFTS and 13C CP-MAS ssNMR characterizations revealed that the enhanced low-concentration CO2 capture is attributed to the formation of a stable six-membered ring structure through the interaction of intramolecular hydrogen bonds between neighboring Zr-OH sites via a chemisorption mechanism.

High temperature capture of low concentration CO2 by Na/Ca-doped lithium orthosilicate with KIT-6 as precursor

Using KIT-6 as the silica source, a series of Li 4 SiO 4 adsorbents (KIT-6-Li 4 SiO 4 ) were synthesized by impregnation precipitation method for high temperature CO 2 capture. Then, the KIT-6-Li 4 SiO 4 -800-4 (KL-800-4) material, was selected to analyze the improvement of the adsorption performance by Ca 2+ /Na + eutectic doping modification. These adsorbents were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and low temperature N 2 adsorption/desorption, and the CO 2 adsorption capacity of them was explored. At 600 °C and under 15 vol% CO 2 , KL-Ca0.03 and KL-Na0.06 sorbents resulted in a CO 2 uptake of 29.17 wt% and 35.35 wt% (close to the theoretical maximum), respectively，which are much higher than that of KL-800-4 (14.73 wt%). After 10 adsorption/desorption cycles, the adsorption capacity of KL-Na0.06 increased by 1.35 wt%. We found that KL-Na0.06 has more advantages compared with traditional lithium orthosilicate and undoped adsorbents, including lower energy consumption, higher CO 2 adsorption capacity and better cycling ability. Finally, the double exponential model had a high degree of fit for the adsorption of CO 2 by Li 4 SiO 4 .

Confinement effects facilitate low-concentration carbon dioxide capture with zeolites

Engineered systems designed to remove CO2 from the atmosphere need better adsorbents. Here, we report on zeolite-based adsorbents for the capture of low-concentration CO2. Synthetic zeolites with the mordenite (MOR)-type framework topology physisorb CO2 from low concentrations with fast kinetics, low heat of adsorption, and high capacity. The MOR-type zeolites can have a CO2 capacity of up to 1.15 and 1.05 mmol/g for adsorption from 400 ppm CO2 at 30 °C, measured by volumetric and gravimetric methods, respectively. A structure-performance study demonstrates that Na+ cations in the O33 site located in the side-pocket of the MOR-type framework, that is accessed through a ring of eight tetrahedral atoms (either Si4+ or Al3+: eight-membered ring [8MR]), is the primary site for the CO2 uptake at low concentrations. The presence of N2 and O2 shows negligible impact on CO2 adsorption in MOR-type zeolites, and the capacity increases to ∼2.0 mmol/g at subambient temperatures. By using a series of zeolites with variable topologies, we found the size of the confining pore space to be important for the adsorption of trace CO2. The results obtained here show that the MOR-type zeolites have a number of desirable features for the capture of CO2 at low concentrations.

Progress and prospects of carbon dioxide capture, EOR-utilization and storage industrialization

Carbon dioxide capture, EOR-utilization and storage (CCUS-EOR) are the most practical and feasible large-scale carbon reduction technologies, and also the key technologies to greatly improve the recovery of low-permeability oil fields. This paper sorts out the main course of CCUS-EOR technological development abroad and its industrialization progress. The progress of CCUS-EOR technological research and field tests in China are summarized, the development status, problems and challenges of the entire industry chain of CO2 capture, transportation, oil displacement, and storage are analyzed. The results show a huge potential of the large-scale application of CCUS-EOR in China in terms of carbon emission reduction and oil production increase. At present, CCUS-EOR in China is in a critical stage of development, from field pilot tests to industrialization. Aiming at the feature of continental sedimentary oil and gas reservoirs in China, and giving full play to the advantages of the abundant reserves for CO2 flooding, huge underground storage space, surface infrastructure, and wide distribution of wellbore injection channels, by cooperating with carbon emission enterprises, critical technological research and demonstration project construction should be accelerated, including the capture of low-concentration CO2 at low-cost and on large-scale, supercritical CO2 long-distance transportation, greatly enhancing oil recovery and storage rate, and CO2 large-scale and safe storage. CCUS-EOR theoretical and technical standard system should be constructed for the whole industrial chain to support and promote the industrial scale application, leading the rapid and profitable development of CCUS-EOR emerging industrial chain with innovation.

Granulation of alkaline metal nitrate promoted MgO adsorbents and the low-concentration CO2 capture performance in the fixed bed adsorber

Magnesium-based adsorbents with the modification of alkaline metal salts are considered the competitive candidates for CO2 capture at intermedium temperature. In this article, the NaNO3 promoted MgO adsorbents were prepared and granulated, and the characterization methods were used to detect the microstructure of the granular adsorbents, including NaNO3 distribution, BET specific surface area, micropore size and microcrystal aggregation. The thermogravimetric analyzer (TGA) tests were carried out to investigate the optimal CO2 adsorption and desorption temperatures and the cyclic stability of the NaNO3 promoted MgO granules. Moreover, the pretreatment of carbonization and calcination was adopted to improve the cyclic stability of the granular adsorbents. Furthermore, the fixed bed adsorber with 40 g NaNO3-MgO granules was used to capture CO2 from 50% CO2 mixture gas with N2 and from 20% CO2 mixture gas with N2, respectively, and the CO2 breakthrough behaviors in the fixed bed were investigated. It was found that NaNO3-MgO adsorbents were suitable for the middle and high-concentration CO2 capture (such as 50% CO2 feed gas) in fixed bed adsorber with the higher CO2 recovery efficiency, but the CO2 recovery efficiency was lower for the low-concentration CO2 capture (such as 20% CO2 feed gas) at ordinary pressure. Because about 10 kPa CO2 partial pressure in the gas phase was needed to overcome CO2 mass transfer resistance in the molten salt layer on MgO surface during adsorption, the appropriate pressurization would improve the low-concentration CO2 capture efficiency in the fixed bed adsorber.

Zinc Containing Small‐Pore Zeolites for Capture of Low Concentration Carbon Dioxide

AbstractThe capture of low concentration CO2 presents numerous challenges. Here, we report that zinc containing chabazite (CHA) zeolites can realize high capacity, fast adsorption kinetics, and low desorption energy when capturing ca. 400 ppm CO2. Control of the state and location of the zinc ions in the CHA cage is critical to the performance. Zn2+ loaded onto paired anionic sites in the six‐membered rings (6MRs) in the CHA cage are the primary sites to adsorb ca. 0.51 mmol CO2/g‐zeolite with Si/Al=ca. 7, a 17‐fold increase compared to the parent H‐form. The capacity is increased further to ca. 0.67 mmol CO2/g‐zeolite with Si/Al=ca. 2 due to more paired sites for zinc exchange. Zeolites with double six‐membered rings (D6MRs) that orient 6MRs into the cages give enhanced uptakes for CO2 adsorption with zinc exchange. The results reveal that zinc exchanged CHA and several other small pore, cage containing zeolites merit further investigation for the capture of low concentration CO2.

Zinc Containing Small‐Pore Zeolites for Capture of Low Concentration Carbon Dioxide

AbstractThe capture of low concentration CO2 presents numerous challenges. Here, we report that zinc containing chabazite (CHA) zeolites can realize high capacity, fast adsorption kinetics, and low desorption energy when capturing ca. 400 ppm CO2. Control of the state and location of the zinc ions in the CHA cage is critical to the performance. Zn2+ loaded onto paired anionic sites in the six‐membered rings (6MRs) in the CHA cage are the primary sites to adsorb ca. 0.51 mmol CO2/g‐zeolite with Si/Al=ca. 7, a 17‐fold increase compared to the parent H‐form. The capacity is increased further to ca. 0.67 mmol CO2/g‐zeolite with Si/Al=ca. 2 due to more paired sites for zinc exchange. Zeolites with double six‐membered rings (D6MRs) that orient 6MRs into the cages give enhanced uptakes for CO2 adsorption with zinc exchange. The results reveal that zinc exchanged CHA and several other small pore, cage containing zeolites merit further investigation for the capture of low concentration CO2.

Tetraethylenepentamine-grafted polyacrylonitrile-poly(methyl methacrylate) hollow fibers for low concentration CO2 capture at ambient temperature

In this work, a new type of solid amine sorbent was developed for low concentration CO2 capture at ambient temperature. Polyacrylonitrile(PAN)-poly(methyl methacrylate)(PMMA) porous hollow fibers were firstly prepared by a wet-spinning process. Tetraethylenepentamine(TEPA) was then grafted onto the porous structure of the hollow fibers. The amine modified hollow fibers denoted as TEPA@PAN-PMMA were characterized by the Fourier transform infrared spectroscopy (FT-IR), thermo-gravimetric analysis(TGA), Brunauer-Emmett-Teller(BET), and scanning electron microscopy(SEM) methods. Performance of the TEPA@PAN-PMMA for CO2 capture was evaluated by passing a 0.3% CO2-N2 gas mixture through the porous matrix of the hollow fibers at ambient temperature. The highest CO2 adsorption capacity reached up to 1.50 mmol g−1 for dry feed, and 3.00 mmol g−1 for wet feed, respectively. Cyclic CO2 adsorption-desorption test indicated that the TEPA@PAN-PMMA sorbents are stable and regenerable.

In-situ amino-functionalization of zeolitic imidazolate frameworks for high-efficiency capture of low-concentration CO2 from flue gas

The capture of low-concentration CO2 from flue gas is an on-going challenge. In this work, a novel series of amino-functionalized zeolitic imidazolate framework-8 materials (ZIF-DIA) was facilely synthesized via in-situ incorporating an large-size amino-functional imidazolium ligand during the synthesis process under atmospheric conditions, and its adsorption performance of CO2 from a simulated flue gas (15 vol% CO2) was investigated. With the introduction of amino-functional imidazolium ligand, the regular hexahedron structure of pure ZIF-8 is gradually converted into cluster-like morphology. The amino-functionalized ZIF materials exhibit high specific surface areas (712–941 m2·g−1), rapid CO2 adsorption rate (≤80 s), excellent CO2 adsorption capacities of up to 6.17 mmol·g−1 under wide temperature range (35–110 °C), overwhelming that of pure ZIF-8 (≤1.96 mmol·g−1) and other reported metal–organic frameworks (MOFs). DFT calculation verified that π-π stacking and hydrogen bonding between imidazole/aromatic rings on ligands and CO2 play crucial role in high CO2 uptake. Excellent recyclability in 10 runs under both low and high temperatures (55 °C, 110 °C) is exhibited, endowing this kind of materials with great potential for practical applications.

Recent progress of green sorbents-based technologies for low concentration CO2 capture

The increased concentration of CO 2 due to continuous breathing and no discharge of human beings in the manned closed space, like spacecraft and submarines, can be a threat to health and safety. Effective removal of low concentration CO 2 from the manned closed space is essential to meet the requirements of long-term space or deep-sea exploration, which is an international frontier and trend. Ionic liquids (ILs), as a widespread and green solvent, already showed its excellent performance on CO 2 capture and absorption, indicating its potential application in low concentration CO 2 capture. In this review, we first summarized the current methods and strategies for direct capture from low concentration CO 2 in both the atmosphere and manned closed spaces. Then, the multi-scale simulation methods of CO 2 capture by ionic liquids are described in detail, including screening ionic liquids by COSMO-RS methods, capture mechanism by density functional theory and molecular dynamics simulation, and absorption process by computational fluid dynamics simulation. Lastly, some typical IL-based green technologies for low concentration CO 2 capture, such as functionalized ILs, co-solvent systems with ILs, and supported materials based on ILs, are introduced, and analyzed the subtle possibility in manned closed spaces. Finally, we look forward to the technology and development of low concentration CO 2 capture, which can meet the needs of human survival in closed space and proposed that supported materials with ionic liquids have great advantages and infinite possibilities in the vital area.

Polyvinyl Chloride-Derived Carbon Spheres for CO2 Adsorption.

Polyvinyl chloride (PVC) is the world's third-most widely produced plastic polymer. Directly transforming PVC to carbonaceous materials for CO2 capture provides an environmentally friendly and attractive strategy to recycle plastics. In this work, a simple and effective method was developed to prepare PVC-derived carbon spheres. In this method, the classical "spheroidization" process shaped the original PVC powders into millimeter spheres, and a special dehalogenation and cross-linking process in the presence of a phase-transfer catalyst transferred the thermoplasticity of the PVC-spheres into thermosetting, which stabilized the shape. Furthermore, by rationally adjusting the activation conditions, the porous structure of the carbon spheres was well optimized. With a specific surface area up to 1738 m2 g-1 and the developed microporous structure, the as-prepared carbon spheres showed not only excellent performance in pure CO2 adsorption (8.93 mmol g-1 , 39.3 wt% at 0 °C and 5.47 mmol g-1 , 24.1 wt% at 25 °C), but also outstanding adsorption capacity and recyclability in low-concentration CO2 capture, even superior to conventional molecular sieves.