Mechanism Of CO2 Adsorption Research Articles

Explainable molecular simulation and machine learning for carbon dioxide adsorption on magnesium oxide

The effects of the adsorption energy of CO2 within MgO at different temperatures were investigated by molecular dynamics simulations and experimentally verified. The adsorption mechanism of CO2 within MgO was discussed and explained qualitatively. The results indicated that the diffusive adsorption of CO2 by MgO was divided into two stages, and the ability of CO2 capture by the cubic MgO performed better than that by spherical MgO. The adsorption of CO2 by the cubic MgO was mainly physical and received the inhibited adsorption behavior at the high-temperature stage (>505 K). Herein, we established a comprehensive dataset of adsorption energies and quantitatively analyzed an adsorption energy prediction model using machine learning techniques. The results demonstrated that Decision Tree Regression (DTR) and K-nearest neighbor (KNN) algorithms offer satisfactory accuracy based on root mean square error (RMSE) and R2 evaluations. This approach enables efficient and precise prediction of adsorption energies without the need for labor-intensive molecular dynamics calculations. Furthermore, we explored the influence of various features (Crystal structure, The number of Mg, The number of CO2, Temperature, Pressure, Volume, and Bond energy) on prediction performance. Lastly, we globally evaluated the relative contributions of each feature across four sets of relatively effective algorithms. This comprehensive analysis enhances our understanding of the adsorption mechanism of magnesium oxide on carbon dioxide and provides valuable insights to guide the design of the next generation of high-performance magnesium oxide materials for carbon capture and storage.

Co-adsorption mechanisms of As(V) and Cd(II) by three-dimensional flower-like Mg/Al/Fe-CLDH synthesized by "memory effect".

Due to the different physical and chemical properties such as surface charge and ion morphology between As(V) and Cd(II), it is challenging to remove As(V) and Cd(II), especially at low concentrations. This study constructed a novel three-dimension nanocomposite adsorbent Mg/Al/Fe-CLDH (CFMA) by "hydrothermal + calcination method". And different initial concentration ratios (Cd: As=1: 2, 1: 1, 2: 1) were used to investigate the removal performance of CFMA for Cd(II) and As(V). When the concentration ratio Cd: As=1: 2, the residual concentrations of As(V) and Cd(II) were 8.7 μg/L and 4.2 μg/L, respectively, which met the drinking water standard; In the co-adsorption system, As(V) and Cd(II) influence each other's adsorption behavior due to the anionic bridge and shielding effect of As(V) on Cd(II), As(V) gradually changed from monolayer adsorption to multi-layer adsorption dominant, while Cd(II) gradually changed from multi-layer adsorption to monolayer adsorption dominant. In this paper, the structure-activity relationship between material structure and synchronous removal of arsenic and cadmium was clarified, and the mechanism of synchronous removal was revealed, which provided technical guidance for synchronous removal of As(V) and Cd(II) from non-ferrous metal smelting wastewater.

Efficient adsorptive removal of Co2+ from aqueous solution using graphene oxide.

This study aimed to utilize synthesized graphene oxide (GO) for adsorptive removal of cobalt ions and investigate the adsorption mechanism using advanced techniques such as X-ray absorption spectra (XAFS). The GO was synthesized via an improved Hummers method, resulting in high surface area (93.7 m2/g) and abundant oxygen-containing functional groups. Various characterizations, including SEM, TEM, Raman, FT-IR, TG, potentiometric titrations, and N2 sorption-desorption measurements, were employed to characterize the GO. The adsorption behavior of GO towards Co2+ was investigated, and the results showed that the adsorption process followed a pseudo-second-order kinetic model and the Langmuir model, with a maximum sorption capacity of 93.7 mg/g. The adsorption process was chemisorption and endothermic, with GO showing adsorption selectivity order of Co2+ > Sr2+ > Cs+. Based on various characterizations such as X-ray absorption near-edge spectroscopy (XANES), extended X-ray absorption fine structure (EXAFS), FT-IR, and XPS, the sorption mechanism of Co2+ onto GO was discussed, with the results indicating that coordination and electrostatic interaction were the primary adsorption mechanisms, with oxygen-containing functional groups playing a vital role. The first coordinating atom for Co2+ was O, and the coordination environment was similar to that of cobalt acetate and CoO. Overall, this study provides comprehensive understanding of the adsorption behavior and mechanism of Co2+ onto GO, highlighting its potential as an effective adsorbent for removing nuclides from aqueous solution.

Synergistic effect and co-adsorption mechanism of a mixed collector on the flotation separation of spodumene from feldspar

In this study, the flotation separation of spodumene from feldspar was achieved using mixed collector of sodium oleate (NaOL)/cetyl trimethylammonium bromide (CTAB). Micro-flotation experiments show that the selective flotation separation of the two minerals could not be achieved in the presence of single collector under the pH range of 2–12, but the they could be effectively separated using mixed collector at the NaOL-to-CTAB molar ratio (MR) of 7:1 at pH 6.0 Artificial mixed minerals tests prove the effective flotation separation effect of the mixed NaOL/CTAB at pH 6.0. Analyses of bubble collision-attachment show that when using mixed NaOL/CTAB as the collector, the bubble could quickly form a three-phase contact (TPC) line on spodumene surface (tTPC=396 ms), but the bubble did not form TPC line on feldspar surface (tTPC＞2000 ms), suggesting a much stronger hydrophobic surface of spodumene. Adsorption amount tests show the much higher adsorption density of mixed NaOL/CTAB on spodumene surface than feldspar, moreover, CTAB promoted the NaOL adsorption on spodumene surface, but it hindered the NaOL adsorption on feldspar surface. The surface and thermodynamic parameters (CMC, γcmc, ∆Gm0, Γmax, Amin) obtained from surface analyses demonstrate higher surface activity and denser molecular arrangement in mixed NaOL/CTAB system than that in the individual system, indicating a positive synergistic effect of mixed collector. Pyrene fluorescence spectrum analyses present the lower critical micelle concentration (CMC) value and polarity of the mixed NaOL/CTAB than their individual components, suggesting that the mixture had much stronger hydrophobicity and was more likely to form micelles than single collector. All the tests were conducted at temperature of 25 ℃.

Co-adsorption mechanism of organic pollutants on NiFe2O4/GO nanostructures: Experimental and molecular dynamics studies

The simultaneous removal of two or more pollutants from an aqueous medium requires a composite adsorbent that can provide sites specific to different adsorbates. But it is difficult to decipher the molecular-level adsorption mechanism under such circumstances. We combine experimental and classical molecular dynamics simulations to gain insight into this research problem. The present research investigates the simultaneous removal of ciprofloxacin (CIP) and methyl orange (MO) from an aqueous medium using a composite of graphene oxide (GO) and superparamagnetic NiFe2O4 nanoparticles. The adsorbent demonstrated economical and efficient magnetic recyclability. The co-adsorption isotherm data for CIP and MO best fitted the Extended Freundlich model, in agreement with the heterogeneous adsorption sites available on the composite. The experimental results were combined with classical molecular dynamics simulations to understand the predominant molecular-level adsorbate-adsorbent interactions. The latter revealed the two adsorbates adsorb to distinctly different adsorption sites on the NiFe2O4/GO composite.

The increasing risk of ammonia volatilization in farmland from the recovery product of magnesium-modified biochar after nitrogen and phosphorus adsorption

Many studies have shown that magnesium modified biochar (MgBC) can recover nutrients from wastewater and be applied as an excellent slow-release fertilizer in farmland. However, the recovery products (NP-loaden MgBC), represented by struvite or magnesium phosphate, have a high degree of self-alkalinity, which may significantly increase the ammonia (NH3) volatilization in farmland. In this study, the optimal adsorption parameters, self-alkaline regulation process and co-adsorption mechanism of MgBC for ammonium ion (NH4+) and phosphate ion (PO43−) were studied through batch experiments. A field experiment was conducted with three treatments, including local conventional fertilization (N1B0) and the application of 5 t·ha−1 or 10 t·ha−1 NP-loaden MgBC in combination with local conventional fertilization (N1B1 and N1B2, respectively), to determine the impact of NP-loaden MgBC on NH3 volatilization, surface water c(NH4+-N) and pH. The results indicated that the maximum NH4+ and PO43− synergistic recovery of MgBC under the optimal adsorption parameters (dosage of 0.6 g·L−1; initial NH4+ and PO43− concentrations of 120 and 60 mg·L−1 and pH of 8) were 59.96 and 98.60 mg·g−1, respectively. Self-regulating alkaline MgBC maintained pH suitable for struvite, and precipitation mechanism controlled the adsorption. The presence of NP-loaden MgBC raised the pH levels in surface water during the basal fertilization stage and increased c(NH4+-N) in surface water during the topdressing stages. This, in turn, led to a significant increase in NH3 volatilization loss during the entire rice-growing period, with N1B1 and N1B2 experiencing a 23.87 % and 48.91 % increase respectively, compared to N1B0. Therefore, it is imperative to take into account the adverse impact of NP-laden MgBC on NH3 loss in paddy fields when considering its application in future field studies.

Modified NiFe-MOF with defects induced by -NH2 and -SH for enhanced adsorption and photocatalytic reduction of CO2

In this study, a Ni-Fe metal-organic framework modified by –NH2 and –SH was synthesized using a simple hydrothermal process for enhancing photocatalytic CO2 reduction. As expected, the N2S-NiFe (NH2-BDC/H4DSBDC, 2:1) displayed excellent photocatalytic CO2 reduction activity and high CO selectivity (12,412.23 μmol g−1 h−1) under visible light irradiation (λ ≥ 420 nm), which is 5 times that of NiFe-MOF. Notably, the excellent photocatalytic performance of N2S-NiFe can benefit from the rich defect trap site caused by the introduction of amino and sulfhydryl groups, accelerating charge transfer and promoting space charge separation, as supported by the photo-electrochemical properties. To better understand the CO2 adsorption mechanism, density functional theory calculations were performed, which revealed that the Niov site has more negative adsorption energy compared with the Feov site. This study provides a simple strategy to establish efficient photocatalysts for CO2 reduction through the modification of organic ligands.

Density functional theory study of high-temperature CO2 adsorption by Li2ZrO3: Effect of typical flue gas components on adsorption energy and electronic properties

Lithium zirconate (Li2ZrO3) is one of the best-performing high-temperature CO2 adsorbents, but the effect of flue gas on its mutual mechanism of action is not clear. The adsorption mechanism of CO2 and flue gas components on the Li2ZrO3 (111) surface is investigated theoretically through density functional theory (DFT), where the selected flue gas components are O2, H2O, and SO2. Theoretical calculations show that O2 exhibits physical adsorption and CO2, H2O, and SO2 exhibit chemisorption on the Li2ZrO3 surface. The energy potential barrier for CO2 adsorption on the Li2ZrO3(111) surface is 0.3 eV. CO2 is gradually desorbed at temperatures above 870 K. When there are flue gas atmospheres present, the desorption temperature of CO2 decreases, to a certain extent. All selected flue gas components inhibit the adsorption of CO2, O2, and H2O, weakening the interaction forces between the surface and CO2 and making it less stable. SO2 has the same adsorption sites as CO2, while SO2 has much higher adsorption energy than CO2. SO2 is more likely to adsorb onto and occupy the active sites of CO2.

Regulating catalytic activity of C2N for the CO oxidation by N2O via deposition of metallic elements: A density functional theory study

Converting N2O and CO into harmless gases is an effective solution for several environmental issues. We investigate the catalytic activity of C2N deposited with Al, Fe and Co for the CO oxidation by N2O by density functional theory (DFT) calculations. In this work, we pondered different adsorption sites of C2N such as N-terminal, C-terminal, and metal-terminal. The reaction pathways and energy barriers of two mechanisms: stepwise adsorption and co-adsorption, are scrutinized and compared. Moreover, the O-terminal and N-terminal pathways for N2O adsorption are pondered. The result indicate that deposited metals greatly decrease the reaction energy barrier for the rate-determining step in both the stepwise and co-adsorption reaction mechanisms. In addition, the stepwise adsorption mechanism is more likely to occur than the co-adsorption mechanism. Al@C2N exhibits the best catalytic effect in the stepwise adsorption mechanism and its energy barrier of the rate-determining step is only 1.08 kcal/mol. Fe@C2N shows superior catalytic activity in the co-adsorption mechanism, and its highest energy barrier is 12.62 kcal/mol.

Towards estimation and mechanism of CO2 adsorption on zeolite adsorbents using molecular simulations and machine learning

The earth's average temperature is being elevated owing to burning of fossil fuels, explicitly releasing enormous amounts of CO2 into the atmosphere. Therefore, effective collection strategies are needed to minimize the concentration of CO2. The current work presents use of molecular simulations to examine CO2 adsorption on zeolites from the zeolite database. Among the 218 zeolites, the Linde Type A zeolite (LTA) stands out as the best for CO2 adsorption with a percentage weight of 69.88% at 298 K and 1000 kPa. This calculated value is in agreement with a recent experimental study that reported 63.65% at 298 K and 0.1 MPa, indicating that our model could be reliable in predicting the CO2 loading capacity. The structural features of the zeolites were also calculated and their significance on CO2 adsorption, evaluated using a machine learning algorithm. Gravimetric surface area seemed to be the most significant structural features. Hence, its feature engineering may expedite adsorption of CO2. Quantum chemical calculations were further used to provide insights into the sorption mechanisms, whereby it is thermodynamically favorable for CO2 to adsorb through carbon bonding as opposed to dissociative adsorption or hydrogen bonding. Finally, the effect of doping the zeolites with selected cations on the loading capacity was investigated, whereby doping LTA with lithium significantly improved the adsorption of CO2.

Highly Cooperative CO2 Adsorption via a Cation Crowding Mechanism on a Cesium-Exchanged Phillipsite Zeolite.

An understanding of the CO2 adsorption mechanisms on small-pore zeolites is of practical importance in the development of more efficient adsorbents for the separation of CO2 from N2 or CH4 . Here we report that the CO2 isotherms at 25-75 °C on cesium-exchanged phillipsite zeolite with a Si/Al ratio of 2.5 (Cs-PHI-2.5) are characterized by a rectilinear step shape: limited uptake at low CO2 pressure (PCO2 ) is followed by highly cooperative uptake at a critical pressure, above which adsorption rapidly approaches capacity (2.0 mmol g-1 ). Structural analysis reveals that this isotherm behavior is attributed to the high concentration and large size of Cs+ ions in dehydrated Cs-PHI-2.5. This results in Cs+ cation crowding and subsequent dispersal at a critical loading of CO2 , which allows the PHI framework to relax to its wide pore form and enables its pores to fill with CO2 over a very narrow range of PCO2 . Such a highly cooperative phenomenon has not been observed for other zeolites.

Highly Cooperative CO2 Adsorption via a Cation Crowding Mechanism on a Cesium‐Exchanged Phillipsite Zeolite

AbstractAn understanding of the CO2 adsorption mechanisms on small‐pore zeolites is of practical importance in the development of more efficient adsorbents for the separation of CO2 from N2 or CH4. Here we report that the CO2 isotherms at 25–75 °C on cesium‐exchanged phillipsite zeolite with a Si/Al ratio of 2.5 (Cs‐PHI‐2.5) are characterized by a rectilinear step shape: limited uptake at low CO2 pressure (PCO2) is followed by highly cooperative uptake at a critical pressure, above which adsorption rapidly approaches capacity (2.0 mmol g−1). Structural analysis reveals that this isotherm behavior is attributed to the high concentration and large size of Cs+ ions in dehydrated Cs‐PHI‐2.5. This results in Cs+ cation crowding and subsequent dispersal at a critical loading of CO2, which allows the PHI framework to relax to its wide pore form and enables its pores to fill with CO2 over a very narrow range of PCO2. Such a highly cooperative phenomenon has not been observed for other zeolites.

A mechanistic study of VO2 reduction on graphene-based electrodes: insights from computational quantum chemistry.

The identity of active sites for redox reactions within vanadium redox flow batteries (VRFB) are still controversial despite decades of research into the matter. Here, we use density functional theory to examine the promise of select surface functional groups as active sites and provide mechanistic insights into the reaction pathway for the positive electrode reaction. The adsorption of electroactive species to phenol and carbene-like edge carbon sites were compared using model aromatic clusters. Though phenol groups were not favorable sites for the chemisorption of VO2+ in either a V-down or O-down approach, carbene-like edge carbon sites readily adsorbed VO2+ via an oxygen-down approach, mimicking gas phase CO2 adsorption mechanisms. Subsequent steps to complete the reaction pathway were a series of proton adsorptions and reaction products desorption. The rate determining step for a reaction pathway using an edge site was the VO2+ desorption step with a Gibbs energy of activation of +84 kcal/mol.

A Robust Squarate-Cobalt Metal-Organic Framework for CO2/N2 Separation.

The separation of CO2 from the industrial post-combustion flue gas is of great importance to reduce the increasingly serious greenhouse effect, yet highly challenging due to the extremely high stability, low cost, and high separation performance requirements for adsorbents under the practical operating conditions. Herein, we report a robust squarate-cobalt metal-organic framework (MOF), FJUT-3, featuring an ultra-small 1D square channel decorated with -OH groups, for CO2/N2 separation. Remarkably, FJUT-3 not only has excellent stability under harsh chemical conditions but also presents low-cost property for scale-up synthesis. Moreover, FJUT-3 shows excellent CO2 separation performance under various humid and temperature conditions confirmed by the transient breakthrough experiments, thus enabling FJUT-3 with adequate potentials for industrial CO2 capture and removal. The distinct CO2 adsorption mechanism is well elucidated by theoretical calculations, in which the hierarchical C···OCO2, C-O···CCO2, and O-H···OCO2 interactions play a vital synergistic role in the selective CO2 adsorption process.

Enhancing Size-Selective Adsorption of CO2/CH4 on ETS-4 via Ion-Exchange Coupled with Thermal Treatment

ETS-4 shows great potential to achieve effective separation of challenging mixtures due to its promising tunability of pores. However, the regulation of pore size is largely limited by its low thermal stability. Here, Na-ETS-4 was synthesized by the hydrothermal method and additionally modified via ion exchange coupled with thermal treatment. Structures of all synthesized samples were examined using a variety of characterization techniques. Both adsorption equilibrium and kinetics of CO2 and CH4 on these adsorbents were evaluated on custom-made adsorption units. In addition, the mechanism of CO2 adsorption on different structural models of ETS-4 was revealed via combining with the molecular dynamics (MD) simulations. Ion exchange largely improves the thermal stability of ETS-4 and its adsorption capacities for CO2 and CH4. Ba-ETS-4-350 exhibits the largest equilibrium selectivity of 12.42 and the greatest Henry’s selectivity of 2178.51. The radial distribution function (RDF) results reveal the main adsorption sites of CO2 in different ETS-4 structures.

Dynamics of Adsorbed CO Molecules on the TiO2 Surface under UV Irradiation

In this work, the UV-stimulated processes in the TiO2–COg system were explored by in situ FTIR spectroscopy and photoelectron spectroscopy. Kinetic dependences of the total band intensity for adsorbed CO and background absorption, as well as the positions of the Fermi level in TiO2 before, during, and after UV irradiation of the system, were analyzed and compared. The observed reversible shift in the adsorption–desorption equilibrium was explained by changing the electronic state of the photocatalyst under UV irradiation. The proposed mechanism of photostimulated CO adsorption and CO re-adsorption in the TiO2–COg system is described in detail. A deflection of reversibility of molecular photodesorption–re-adsorption dynamics is caused by the side reaction of CO photooxidation and the formation of strongly bound surface carbonates.

The selective adsorption mechanism of CO2 from biomass pyrolysis gas on N-doped carbon materials with an electric field: A first-principles study

Renewable biomass resources can be efficiently converted into fuels, materials, or chemicals by pyrolysis. The selective adsorption of CO2 from the biomass pyrolysis gas is beneficial for its further utilization. Herein, density functional theory (DFT) was employed to reveal the adsorption mechanism of CO2 in pyrolysis gases by the graphite-N-, pyridine-N-, and pyrrole-N-doped graphene models. The impacts of the electric field and the influence of other biomass pyrolysis gas components on CO2 adsorption were particularly explored. The results show that the three graphite-N atoms doped graphene (3N-G) can achieve chemical adsorption of CO2 with the electric field. While physical adsorption occurs when CO2 adsorbs on the surface of the other graphene models regardless of the electric field. In addition, H2, CO, CH4, and C2H4 are physically adsorbed on 3N-G, and their adsorption is not affected by the electric field. The co-adsorption of CO2 with H2, CO, CH4, and C2H4 on 3N-G with an electric field indicates that CO2 is chemisorbed and other gas molecules are physisorbed. In summary, 3N-G can achieve selective adsorption of CO2 when the electric field is adopted. The present work lays a foundation for the separation and purification of biomass pyrolysis gas components and CO2 capture.

Assessment of adsorption materials for carbon capturing and storage in the context of carbon neutrality

In order to avoid the harm caused by global warming, carbon capture and store (CCS) technology has become a global hot topic. CO2 adsorption materials are an important basis for the realization of CCS. This paper explores the CO2 adsorption mechanisms of the currently widespread shale reservoirs, metal-organic framework (MOF), covalent-organic framework (COF), activated carbon and evaluated the relevant factors affecting their adsorption capacity. Through the exchange of CO2 and CH4, shale reservoir is a natural material with great CO2 adsorption and storage potential. However, due to the high implementation cost and the uncertainty of porosity, this technology is considered to be immature. MOF and COF have different chemical bonds, but they are both crystalline compounds with tunable porosity and internal surface area. They are very ideal CO2 adsorption materials. However, the main disadvantage of MOF and COF lies in their instability. Moreover, activated carbon is considered to be the adsorption material with the lowest production cost among the four. The adsorption performance of activated carbon is related to its raw materials, internal surface area, pore properties and external functional groups. However, activated carbon ashes are likely to cause secondary environmental pollution. In the future, it is necessary to improve the prediction accuracy of the adsorption potential of shale reservoirs, solve the unstable characteristics of MOF and COF, and maximize the adsorption performance of activated carbon in an environmentally friendly manner. The significance of this article is to provide theoretical support for the optimization and development of physical adsorption materials in the future.

Machine learning implemented exploration of the adsorption mechanism of carbon dioxide onto porous carbons

Adsorption of CO2 on porous carbons has been identified as one of the promising methods for carbon capture, which is essential for meeting the sustainable developmental goal (SDG) with respect to climate action, i.e., SDG 13. This research implemented six supervised machine learning (ML) models (gradient boosting decision tree (GBDT), extreme gradient boosting (XGB), light boost gradient machine (LBGM), random forest (RF), categorical boosting (Catboost), and adaptive boosting (Adaboost)) to understand and predict the CO2 adsorption mechanism and adsorption uptake, respectively. The results recommended that the GBDT outperformed the remaining five ML models for CO2 adsorption. However, XGB, LBGM, RF, and Catboost also represented the prediction in the acceptable range. The GBDT model indicated the accurate prediction of CO2 uptake onto the porous carbons considering adsorbent properties and adsorption conditions as model input parameters. Next, two-factor partial dependence plots revealed a lucid explanation of how the combinations of two input features affect the model prediction. Furthermore, SHapley Additive exPlainations (SHAP), a novel explication approach based on ML models, were employed to understand and elucidate the CO2 adsorption and model prediction. The SHAP explanations, implemented on the GBDT model, revealed the rigorous relationships among the input features and output variables based on the GBDT prediction. Additionally, SHAP provided clear-cut feature importance analysis and individual feature impact on the prediction. SHAP also explained two instances of CO2 adsorption. Along with the data-driven insightful explanation of CO2 adsorption onto porous carbons, this study also provides a promising method to predict the clear-cut performance of porous carbons for CO2 adsorption without performing any experiments and open new avenues for researchers to implement this study in the field of adsorption because a lot of data is being generated.

Potassium Citrate-Activated Porous Carbon Nanostructures for CO2 Adsorption and Electroreduction

CO2 capture via adsorption has been widely explored and is viewed as one of the most effective and green solutions to address the high CO2 concentration globally. However, the formation of intermediates during CO2 adsorption and the synthesis of the adsorbent, activated carbon, still need to be resolved. In this study, potassium citrate-activated carbon (ACK) samples were prepared. The synergistic effects of the potassium content and reaction temperature (600 and 1000 °C) were examined. In the synthesis of potassium citrate-activated carbon, potassium citrate was converted to KOH, K2CO3, and K2O and evaporated as metallic potassium vapor followed by intercalation into the activated carbon lattice, forming a micro- and mesoporous nanostructure, which is advantageous for CO2 capture and electrocatalytic reduction. In addition, trace potassium in the ACK sample acted as a reactive site to redistribute and facilitate electron transfer, enabling enhanced CO2 activation and reduction. The ACK samples exhibited strong dual-site bonding of CO2 to the Lewis basic sites, forming b-CO32– intermediates by the physical adsorption through the abundant porous structure of the ACK sample and chemical adsorption by its strong Lewis basicity. In summary, our work presents detailed analyses to understand the mechanism of CO2 adsorption using activated carbon as an effective adsorbent.