CO2 Adsorption Research Articles

Nanoscale Pore Evolution of Terrestrial Shale with Thermal Maturation Level Increase Induced by Hydrous Pyrolysis

A series of terrestrial shale samples with different thermal maturities were subjected to hydrous artificial pyrolysis to study the evolution of terrestrial shale pores. The original shale was obtained from the terrestrial interval of a core sample, the total organic carbon (TOC) content was 8.34 wt%, and the vitrinite reflectance (Ro) was 5.31%. The original shale core was cut into eight parts, which were heated at temperatures of 300, 350, 400, 420, 450, 500, 550, and 600 °C to obtain samples with different thermal maturities. The pore size distribution (PSD), pore volume (PV), specific surface area (SSA), and pore types were investigated via CO2 and N2 adsorption tests and field emission scanning electron microscopy (FE-SEM). Many organic matter (OM) pores and mineral pores were observed via FE-SEM with increasing thermal maturity. The total PV and SSA increased until the sample reached 500 °C and then decreased, and the mesopore volume followed this trend. The micropore volume first decreased, increased until the sample reached 500 °C, and then decreased; the macropore volume increased to a peak in the sample pyrolyzed at 420 °C and then remained stable. Pores with sizes ranging from 10 to 30 nm were the predominant contributors to the shale pore volume. The SSA was affected by pores with diameters less than 20 nm, which accounted for approximately 54% of the SSA. The rate of OM conversion influenced pore creation.

Supramolecular Preorganization of Amine‐functionalized Diacetylene Monomers in their Crystals Allows their Topochemical Polymerization to Polydiacetylenenes Capable of CO2 Capture

We designed and synthesized three diacetylene monomers M1‐M3 having two NH2 groups. As anticipated, the NH2 groups aided the preorganization of these monomers by N‐H…N hydrogen bonding. In the crystals of monomer M1 and M2, the intermolecular N–H…N hydrogen bonding preorganized the diyne units in an orientation suitable for their topochemical polymerization, but in the case of monomer M3, the distance was slightly larger than that recommended for the topochemical reaction. However, upon heating, all the three monomers underwent topochemical polymerization to yield polydiacetylenes P1‐P3 respectively. All three polymers have been characterized using PXRD, Raman, MALDI‐TOF and solid‐state UV spectroscopy. Furthermore, we investigated the abilities of these amine‐functionalized polymers to capture CO2 gas. Polymer P1, which had a larger surface area, demonstrated the highest CO2 adsorption capacity of 1.28 mmol g−1 at 273 K and 1 bar, compared to the other two polymers.

Di-functional pH-responsive amphiprotic polymer composite particles for efficient adsorption of aqueous CO2

Di-functional pH-responsive amphiprotic polymer composite particles for efficient adsorption of aqueous CO2

Titanium Dioxide and Photocatalytic CO2 Reduction: A Detailed Review of the Current Status and Future Prospects

A significant amount of carbon dioxide is released into the atmosphere as a result of the extensive usage of fossil fuels. The photocatalytic reduction and conversion of CO2 under visible light into alternative renewable solar fuels or other oxygenated products (methane, formaldehyde, methanol, and formic acid) are practical and efficient methods for reducing atmospheric carbon pollution. Functional materials containing titanium dioxide (TiO2) have attracted significant interest for the photocatalytic reduction of CO2. In this direction, many studies have been conducted in recent years, especially on solar energy harvesting and the charge separation, adsorption, activation, and reduction of CO2 on enhanced TiO2. Recent studies have shown that brookite TiO2 (BT) was the most active photocatalyst, followed by rutile and anatase. Therefore, this study aims to review in detail the recent advances in the development of selective and active catalysts for photocatalytic CO2 reduction using titanium dioxide with a brookite structure. This review evaluates the most common methods for obtaining BT. It discusses various engineered strategies, including doping with metallic or non-metallic heteroatoms, addition of a co-catalyst, formation of heterojunctions, and other algorithms to improve the CO2 reduction mechanism. The influence of another phase and crystal facets on the photocatalytic CO2 reduction reaction are discussed in detail. The problems associated with BT-based photocatalysts, namely, their modest visible-light absorption, slow interfacial charge separation, and poor surface catalytic dynamics, are further discussed, along with possible solutions. To stimulate additional research in this field, the difficulties and potential advantages of photocatalytic CO2 conversion methods are discussed.

Comparative analysis of functional group effects on CO2, CH4, CO, and N2 adsorption in UiO-66 and its derivatives

ABSTRACT This work focuses on the effect of organic linker functionality on the adsorption characteristics of CO2, CH4, CO, and N2 over UiO-66, UiO-66-NH2, UiO-66-NO2, UiO-66-COOH, and UiO-66-(COOH)2. Introducing polar and complex functional groups such as – NH2, –NO2, –COOH, and –(COOH)2 improved the adsorption capacity but also reduced the free volume, negatively impacting adsorption. In the low-pressure region, functionality played a dominant role, whereas at saturation, the pore volume of Metal-Organic Frameworks contributed more to adsorption uptake. For all studied gases, a Type-I isotherm was observed. The isotherms were modeled using the virial equation, and model parameters were used to calculate the enthalpies of adsorption. Ideal Adsorbed Solution Theory was used to predict the selectivity of binary mixtures. The selectivity of CO2 over CH4, CO, and N2 showed that introducing larger and more complex functional groups caused a sudden decrease in selectivity with increasing temperature; this difference was more significant at lower temperatures and negligible at higher temperatures.

A Comprehensive Review on Advancements in Modification Strategies of Polymer Blends for Enhanced Carbon Dioxide Capture and Reuse

ABSTRACTCarbon dioxide (CO2) is emitted into the atmosphere through the combustion of fossil fuels and various industrial processes, and it is presently regarded as a significant factor in global warming. Carbon capture and storage (CCS) stands out as a prominent strategy put forward to address CO2 emissions. This study aims to provide a comprehensive overview of recent developments in CO2‐based polymers, focusing on sustainable biopolymers, including copolymers and polymer blends. A thorough analysis of CO2 co‐polymers as components in polymer blends is conducted, focusing on the capture of CO2. In recent years, carbon capture technology has attracted considerable focus as a strategy to mitigate the negative effects of increasing CO2 levels in the environment. The process of developing polymer blends entails merging two or more polymeric substances to harness their distinct advantages. This investigation assessed polyethylene glycol (PEG), polyether sulfone (PES), polyurethane (PU), and polyimide (PI) based on their chemical properties as promising polymer blends for the efficient separation of CO2. Advances in polymer blend modifications for improved CO2 capture and reuse are highlighted in this review, with a focus on strategies such as chemical functionalization (e.g., amine or hydroxyl groups), the utilization of porous materials, and the integration of hybrid systems, delving into CO2 adsorption efficiency, selectivity, and reusability. The paper also examines novel materials' potential for CO2‐to‐product conversion, such as bio‐based polymers and nano‐engineered blends. The main obstacles and potential paths for applications that are sustainable and scalable are described.

Research on the adsorption capacity and mechanism of carbon dioxide by ion exchange resin loaded with metal–organic cages

AbstractMetal–organic cages (MOCs), a novel type of porous material, have shown great potential in the adsorption and separation of CO2 gas. Zirconium‐based metal–organic cages (Zr‐MOCs) have garnered special attention because of their outstanding stability and high solubility. Nevertheless, due to its powdery nature and the tendency for easy aggregation, its application in the industrial field is limited. Here, drawing inspiration from water treatment, the inexpensive and stable ionic exchange resin D001 was employed as the supporting material for loading Zr‐MOCs, and D001‐Zr‐MOC was prepared. The adsorption capacity of D001‐Zr‐MOC for CO2 from the mixed gas (15% CO2/85% N2) under diverse loads of Zr‐MOCs, various temperatures, and different gas flow rates was investigated, and its cyclic adsorption performance for CO2 was determined. The adsorption mechanism of CO2 on D001‐Zr‐MOC was probed by means of adsorption energy, adsorption isotherm, adsorption heat, and diffusion coefficient. The results showed that the maximum CO2 adsorption capacity of D001‐Zr‐MOC was 3.96 mmol/g. The adsorption capacity decreased by merely 4.62% after 10 adsorption/desorption cycles. The adsorption energy and adsorption heat of D001‐Zr‐MOC for CO2 molecules are relatively high, which indicates that D001‐Zr‐MOC has good adsorption capacity and selectivity for CO2 molecules. The adsorption of CO2 is regarded as a typical Langmuir monolayer adsorption, and it is verified that a chemical reaction occurred between CO2 and the adsorbent. CO2 possesses a higher diffusion coefficient, and the excellent cyclic adsorption capacity of D001‐Zr‐MOC is verified.

Copper-Catalysed Electrochemical CO2 Methanation via the Alloying of Single Cobalt Atoms.

The electrochemical reduction of carbon dioxide (CO2) to methane (CH4) presents a promising solution for mitigating CO2 emissions while producing valuable chemical feedstocks. Although single-atom catalysts have shown potential in selectively converting CO2 to CH4, their limited active sites often hinder the realization of high current densities, posing a selectivity-activity dilemma. In this study, we developed a single-atom cobalt (Co) doped copper catalyst (Co1Cu) that achieved a CH4 Faradaic efficiency exceeding 60% with a partial current density of -482.7 mA cm-2. Mechanistic investigations revealed that the incorporation of single Co atoms enhances the activation and dissociation of H2O molecules, thereby lowering the energy barrier for the hydrogenation of *CO intermediates. In situ spectroscopic experiments and density functional theory simulations further demonstrated that the modulation of the *CO adsorption configuration, with stronger bridge-binding, favours deep reduction to CH4 over the C-C coupling or CO desorption pathways. Our findings underscore the potential of Co1Cu catalysts in overcoming the selectivity-activity trade-off, paving the way for efficient and scalable CO2-to-CH4 conversion technologies.

Copper‐Catalysed Electrochemical CO2 Methanation via the Alloying of Single Cobalt Atoms

The electrochemical reduction of carbon dioxide (CO2) to methane (CH4) presents a promising solution for mitigating CO2 emissions while producing valuable chemical feedstocks. Although single‐atom catalysts have shown potential in selectively converting CO2 to CH4, their limited active sites often hinder the realization of high current densities, posing a selectivity‐activity dilemma. In this study, we developed a single‐atom cobalt (Co) doped copper catalyst (Co1Cu) that achieved a CH4 Faradaic efficiency exceeding 60% with a partial current density of ‐482.7 mA cm‐2. Mechanistic investigations revealed that the incorporation of single Co atoms enhances the activation and dissociation of H2O molecules, thereby lowering the energy barrier for the hydrogenation of *CO intermediates. In situ spectroscopic experiments and density functional theory simulations further demonstrated that the modulation of the *CO adsorption configuration, with stronger bridge‐binding, favours deep reduction to CH4 over the C‐C coupling or CO desorption pathways. Our findings underscore the potential of Co1Cu catalysts in overcoming the selectivity‐activity trade‐off, paving the way for efficient and scalable CO2‐to‐CH4 conversion technologies.

Stabilizing Lattice Oxygen of Bi2O3 by Interstitial Insertion of Indium for Efficient Formic Acid Electrosynthesis

Bismuth oxide (Bi2O3) emerges as a potent catalyst for converting CO2 to formic acid (HCOOH), leveraging its abundant lattice oxygen and the high activity of its Bi‐O bonds. Yet, its durability is usually impeded by the loss of lattice oxygen causing structure alteration and destabilized active bonds. Herein, we report an innovative approach via the interstitial incorporation of indium (In) into the Bi2O3, significantly enhancing bond stability and preserving lattice oxygen. The optimized In‐Bi2O3‐100 catalyst achieves over 90% Faradaic efficiency for HCOOH production across a wide potential range, in both H‐cells and flow cells, maintaining robust stability after 100 hours of continuous operation. In‐situ surface‐enhanced infrared absorption spectroscopy and theoretical calculations reveal that the interstitial In doping precisely tunes the adsorption of CO2* and OCHO* intermediate, facilitating rapid conversion. Further in‐situ Raman spectroscopy confirms the role of In bolstering the oxidized structure's stability within Bi2O3, critical for sustaining lattice oxygen during electrochemical CO2 reduction.

Stabilizing Lattice Oxygen of Bi2O3 by Interstitial Insertion of Indium for Efficient Formic Acid Electrosynthesis.

Bismuth oxide (Bi2O3) emerges as a potent catalyst for converting CO2 to formic acid (HCOOH), leveraging its abundant lattice oxygen and the high activity of its Bi-O bonds. Yet, its durability is usually impeded by the loss of lattice oxygen causing structure alteration and destabilized active bonds. Herein, we report an innovative approach via the interstitial incorporation of indium (In) into the Bi2O3, significantly enhancing bond stability and preserving lattice oxygen. The optimized In-Bi2O3-100 catalyst achieves over 90% Faradaic efficiency for HCOOH production across a wide potential range, in both H-cells and flow cells, maintaining robust stability after 100 hours of continuous operation. In-situ surface-enhanced infrared absorption spectroscopy and theoretical calculations reveal that the interstitial In doping precisely tunes the adsorption of CO2* and OCHO* intermediate, facilitating rapid conversion. Further in-situ Raman spectroscopy confirms the role of In bolstering the oxidized structure's stability within Bi2O3, critical for sustaining lattice oxygen during electrochemical CO2 reduction.

Simultaneously Enhanced Permeability and Selectivity of Pebax-1074-Based Mixed-Matrix Membrane for CO2 Separation

Membrane technology is a promising methodology for carbon dioxide separation due to its benefit of a small carbon footprint. However, the trade-off relationship between gas permeability and selectivity is one obstacle to limiting its application. Herein, branched polyethyleneimine (BPEI) containing a rich amino group was successfully grafted on the surface of the metal–organic framework (MOF) of AIFFIVE-1-Ni (KAUST-8) through coordination between N in BPEI and open metal sites in the MOF and with the resultant maintained BET surface area and pore volume. Both the strengthened CO2 solubility coefficients comig from the additional CO2 adsorption sites of amino groups in BPEI and the reinforced CO2 diffusivity coefficients originating from the fast transport channels created by KAUST-8 led to the promising CO2 separation performance for KAUST-8@BPEI/Pebax-1074 MMM. With 5 wt.% KAUST-8@BPEI loading, the MMM showed the CO2 permeability of 156.5 Barrer and CO2/N2 selectivity of 16.1, while the KAUST-8-incorporated MMM (5 wt.% loading) only exhibited the CO2 permeability of 86.9 Barrer and CO2/N2 selectivity of 13.0. Such enhancement is superior to most of the reported Pebax-1074-based MMMs for CO2 separation indicating a wide application for the coordination method for MOF fillers with open metal sites.

Mechanistic Insights into CO2 Adsorption of Li4SiO4 at High Temperature

The development of materials with high adsorption capacity for capturing CO2 from industrial exhaust gases has proceeded rapidly in recent years. Li4SiO4 has attracted attention due to its low cost, high capture capacity, and good cycling stability for direct high-temperature CO2 capture. Thus far, the CO2 adsorption mechanism of Li4SiO4 is poorly understood, and detailed phase transformations during the CO2 adsorption process are missing. Here, aided by in situ X-ray diffraction and in situ Raman spectroscopy, we find that Li4SiO4 reacts with CO2 to form Li2SiO3 and Li2CO3 in CO2 atmosphere at 973 K, with no detectable involvement of crystalline Li2O during the adsorption process. Moreover, we observe a formation of stepped structures in the Li4SiO4 surface after CO2 adsorption by scanning electron microscopy. To illustrate the formation of stepped structures, we propose a modified double-shell mechanism, suggesting a possible two-dimensional nucleation and growth of Li2CO3. This work provides a deeper understanding of the CO2 adsorption mechanism and paves a way for further optimization of Li4SiO4-based adsorbents.

CO2 Adsorption Using Graphene-Based Materials: A Review

CO2 Adsorption Using Graphene-Based Materials: A Review

Synthesis and characterization of advanced Ad-UiO-66@NGO composite for efficient CO2 capture and CO2/N2 adsorption selectivity.

Highly effective adsorbents, with their impressive adsorption capacity and outstanding selectivity, play a pivotal role in technologies such as carbon capture and utilization in industrial flue gas applications, leading to significant reductions in greenhouse gas emissions. This study aims to synthesize advanced composites via solvothermal methods, incorporating a defective Zirconium-based MOF and amine-functionalized graphene oxide. The main objective is to enhance the CO2 adsorption capacity of the composite and improve its CO2/N2 separation selectivity. The samples were characterized using XRD, FT-IR, TGA, FE-SEM, and nitrogen adsorption and desorption analysis. The composites' gas uptake capacity toward pure CO2 and N2 adsorption were tested at various temperatures and pressure ranges of 1-9 bar. The resulting amino-defective UiO-66/NGO composite containing 15 wt.% of amine-modified GO, displayed the highest CO2 uptake capacity of 15.13 mmol/g at 298 K and 9 bar, representing a remarkable 48% increase compared to the pristine MOF. Furthermore, isotherm and kinetic modeling showed a high level of agreement between the experimental data and the Freundlich and Elovich models, as indicated by their R2 values of 0.998 and 0.973, respectively. Moreover, the thermodynamic evaluation confirmed the exothermic and the spontaneity of the reaction. Furthermore, the adsorbent's CO2/N2 selectivity was evaluated using the ideal adsorbed solution theory, revealing a remarkable selectivity value of 148. The regenerability evaluation through cyclic adsorption experiments showed that the optimized composite maintained CO2 adsorption reversibility at over 81.50% after 55 adsorption-desorption cycles.

Designing cellulose based biochars for CO2 separation using molecular simulations

This study investigates the pyrolysis mechanism of cellulose using reactive molecular dynamics simulations to prepare biochars for CO2 separation applications. Six biochars with densities ranging from 0.160 to 0.987 g/cm³ were prepared, and their performance in adsorbing CO2, CH4, and N2 gases, as well as CO2/CH4 and CO2/N2 gas mixtures, was evaluated using Grand Canonical Monte Carlo (GCMC) simulations. The adsorption isotherms were fitted to the Dual-Site Langmuir (DSL) equation, and subsequently, the isosteric heat of adsorption, Gibbs free energy, and entropy changes were calculated. It was found that the results indicated that the density of biochar had a strong impact on gabs adsorption. CO2 had much better interactions with biochars than CH4 and N2. The 0.351 g/cm³-density biochar presented the highest selectivity for CO2. The effect of water vapor was also covered which remarkably decreased the adsorption of CO2 by the competition of active sites for adsorption. These results indicate that optimized cellulose-derived biochars could be a promising material for CO2 separation in sustainable gas purification technologies.

Influence of Monomer Size on CO2 Adsorption and Mechanical Properties in Microporous Cyanate Ester Resins

Influence of Monomer Size on CO2 Adsorption and Mechanical Properties in Microporous Cyanate Ester Resins

Platinum-Nickel@High-Entropy Alloy Core@Satellite Nanowires as Efficient Bifunctional Electrocatalysts for PEMFC.

The optimized composition and precisely tailored structure configuration play critical roles in enhancing the catalytic reaction kinetics. Here we report a distinctive core@satellite strategy for designing the advanced platinum-nickel@platinum-nickel-copper-cobalt-indium high-entropy alloy nanowires (Pt3Ni@HEA NWs) as efficient bifunctional catalysts in the proton exchange membrane fuel cell. Impressively, the Pt3Ni@HEA NWs/C shows 19.4/15.3 times higher mass/specific activity than that of commercial Pt/C for the oxygen reduction reaction. More importantly, synchronously as the cathodic and anodic catalysts, it can achieve a high membrane electrode assembly power density of 1653.5 mW cm-2 and long-term stability (only 3.9% voltage loss) for 280 h, largely outperforming those of commercial Pt/C. The weakened Pt-CO binding strength, quick removal of CO with linear adsorption, and favorable CO adsorption form contribute to the high performance of Pt3Ni@HEA NWs/C. This core@satellite strategy provides a new paradigm to develop the comprehensively efficient Pt-based functional catalysts for fuel cells and beyond.

CO Cryo-sorption as a Surface-sensitive Spectroscopic Probe of the Active Site Density of Single-atom Catalysts.

Quantifying the number of active sites is a crucial aspect in the performance evaluation of single metal-atom electrocatalysts. A possible realization is using adsorbing gas molecules that selectively bind to the single-atom transition metal and then probing their surface density using spectroscopic tools. Herein, using in situ X-ray photoelectron (XPS) and near edge X-ray absorption fine structure (NEXAFS) spectroscopy, we detect adsorbed CO gas molecules on a FeNC oxygen reduction single atom catalyst. Correlating XPS and NEXAFS, we develop a simple surface- and chemically-sensitive protocol to accurately and quickly quantify the active site density. Density functional theory-based X-ray spectra simulations reaffirm the assignment of the spectroscopic fingerprints of the CO molecules adsorbed at Fe-N4-C sites, and provide additional unexpected structural insights about the active site needed to explain the low-temperature CO adsorption. Our work represents an important step towards an accurate quantitative catalytic performance evaluation, and thus towards developing reliable material design principles and catalysts.

Long-Range Metal-Sorbent Interactions Determine CO2 Capture and Conversion in Dual-Function Materials.

Carbon capture and utilization involve multiple energy- and cost-intensive steps. Dual-function materials (DFMs) can reduce these demands by coupling CO2 adsorption and conversion into a single material with two functionalities: a sorbent phase and a metal for catalytic CO2 conversion. The role of metal catalysts in the conversion process seems salient from previous work, but the underlying mechanisms remain elusive and deserve deeper investigation to achieve maximum utilization of the two phases. Here, preformed colloidal Ru nanoparticles were deposited onto a "NaOx"/Al2O3 sorbent to prepare prototypical DFMs with controlled phases for CO2 capture and hydrogenation to CH4. Ru addition was found to double the high-temperature CO2 adsorption capacity by activating the "NaOx"/Al2O3 sorbent phase during a reductive pretreatment step. Most importantly, low Ru loadings were sufficient to ensure maximum CO2 adsorption and conversion. This was attributed to the key role of the metal-sorbent interactions, wherein Ru was required to hydrogenate strongly bound CO2 on the "NaOx"/Al2O3 sorbent to CH4 via the H2 activated on Ru. This interaction facilitated rate-determining carbonate migration and subsequent hydrogenation at the metal-sorbent interface. Overall, Ru controlled the CO2 hydrogenation reaction rate, while the "NaOx"/Al2O3 sorbent dictated the CO2 uptake capacity. By controlling metal-sorbent interactions at the molecular level, we demonstrate the critical role of the two phases and their synergy, facilitating the design of DFMs with maximum CO2 capture and conversion efficiency.