High-performance CO2 Capture Research Articles

Stacked nano FAU zeolite as hierarchical Murray material for enhancing CO2 diffusion kinetics

Zeolite materials are widely used in the field of carbon capture and storage (CCS) due to their high specific surface area, good stability, and low cost. However, the microporous structure of zeolite is not conducive to the mass transfer and diffusion processes, which limits the efficiency and practical application of CO2 capture. In this study, we designed a hierarchical Murray material consisting of ultra-small particle size (<20 nm) zeolite stacks based on Murray's law to enhance the diffusion kinetics of CO2. The results demonstrate that the material exhibits a CO2 adsorption capacity of 107.07 cm3·g−1 and a CO2/N2 selectivity of 120.58, meeting the requirements for high-performance CO2 capture materials. Kinetic CO2 adsorption and breakthrough experiments confirm that the nano-FAU zeolite enables fast and efficient CO2 capture compared to micron-sized zeolite. The stacked nano-zeolites with hierarchical pore structure not only shorten the diffusion path but also facilitate the surface permeation process, which contributes to improved diffusion kinetics. This work provides a valuable strategy for the development of CO2 adsorption materials with high mass transfer rates.

Porous Carbon Derived from Poplar Catkins and Its High-performance CO2 Capture

Porous Carbon Derived from Poplar Catkins and Its High-performance CO2 Capture

Solar thermal swing adsorption on porous carbon monoliths for high-performance CO2 capture

Solar thermal swing adsorption on porous carbon monoliths for high-performance CO2 capture

Rapid Fabrication of High-Permeability Mixed Matrix Membranes at Mild Condition for CO2 Capture.

Mixed matrix membranes (MMMs), conjugating the advantages of flexible processing-ability of polymers and high-speed mass transfer of porous fillers, are recognized as the next-generation high-performance CO2 capture membranes for solving the current global climate challenge. However, controlling the crystallization of porous metal-organic frameworks (MOFs) and thus the close stacking of MOF nanocrystals in the confined polymer matrix is still undoable, which thus cannot fully utilize the superior transport attribute of MOF channels. In this study, the "confined swelling coupled solvent-controlled crystallization" strategy is employed for well-tailoring the in-situ crystallization of MOF nanocrystals, realizing rapid (<5 min) construction of defect-free freeway channels for CO2 transportation in MMMs due to the close stacking of MOF nanocrystals. Consequently, the fabricated MMMs exhibit approximately fourfold enhancement in CO2 permeability, i.e., 2490 Barrer with a CO2 /N2 selectivity of 37, distinctive antiplasticization merit, as well as long-term running stability, which is at top-tier level, enabling the large-scale manufacture of high-performance MMMs for gas separation.

Modeling of pre-combustion carbon capture with CO2-selective polymer membranes

CO2-selective polymer membranes were recently applied to pilot-scale and bench-scale pre-combustion capture and the obtained CO2 capture ratios were reported to be less than 90%, which limits their application in industrial processes such as IGCC plants. This work is aimed to explore the possibility of achieving a CO2 capture ratio >95% and CO2 purity >95% in a gas-separation unit equipped with currently-available CO2-selective polymer membranes. A mathematical model for single-stage membrane gas separation was developed, and the effect of membrane characteristics (permeance and selectivity), as well as the operating parameters such as feed and permeate pressure, and feed flow rate on the performance of CO2 capture was investigated. The simulation results reveal the optimal conditions that are necessary for a high-performance CO2 capture process using the real industrial syngas and highlight the potential of facilitated transport membranes for CO2 removal in both the oxygen-blown and air-blown IGCC processes.

Design of N-doped carbon materials using self-template strategy for high-performance supercapacitor electrodes and CO2 capture

Hierarchical N-doped porous carbons were synthesized using a self-templated and solvent-free assembly approach via directly heating green polyaspartic acid potassium. The samples prepared under different calcining temperatures were characterized, which exhibited the structural features of high pore volume (0.88–1.75 cm 3 /g) and large specific surface area (1592–3133 m 2 /g). Subsequently, these samples were applied for selective CO 2 capture and supercapacitor electrodes. The N-PCM-900 prepared at 900 °C afforded superb electrochemical performance, including extremely large specific capacitance (346 F/g at 1 A/g), high-rate capability (charge-discharge profiles at 20 A/g), and excellent cycle stability (96.86 % retention after 1000 cycles) in KOH electrolyte (6 M). Moreover, N-PCM-900 simultaneously provided high CO 2 adsorption ability (4.63 mmol/g) at 273 K, and high ideal adsorption solution theoretical value (25) for capturing CO 2 /N 2 at 298 K. The multifunctional porous carbon presented herein exhibited great potential for electrochemical energy storage and gas adsorption/separation. • A self-templated and solvent-free assembly approach was developed for the synthesis of hierarchical N-doped porous carbon. • The samples exhibited the structural features of high pore volume (1.75 m 3 g) and large specific surface area (3133 m 2 g). • High specific capacitance (161 F/g) and stability (99.4 % after 1000 cycles) are obtained. • Excellent CO 2 adsorption capacity (4.21 mmol/g) at 273 K and IAST selectivity (25) are gave.

Li-decorated β1-graphyne for high-performance CO2 capture and separation over N2

The selective CO2 adsorption is of great significance to many energy and environment-related processes. Herein, CO2/N2 adsorption and separation in Li-doped 2D graphyne allotrope (β1-GY) were studied by using grand canonical Monte Carlo simulation and density(GCMC) functional theory approaches(DFT). The results showed that Li atoms were stably combined with β1-GY and the binding energy was −2.85−−3.60 eV, which ensured the structural stability of Li-doped β1-graphyne (Li-β1-GY) for CO2/N2 adsorption and separation. Different Li doping types were evaluated, and five Li-β1-GY structures were screened, including the a, b, c, ac, and bc structures. Li doping provided more adsorption sites and improved the CO2 adsorption performance. Among all Li-β1-GYs, the ac structure showed the best CO2 adsorption performance. The CO2 adsorption capacity of ac structure reached 11.10 mmol−1 g−1 at 298 K and 100 kPa, which was higher than the well-known metal–organic framework Mg-MOF-74 (∼8.60 mmol−1 g−1) under the same condition. At 298 K and 100 kPa, the CO2/N2 selectivity reached 354. The gas distribution confirmed that CO2 was adsorbed around the Li and C atoms and demonstrated the significant improvement of C atoms around Li atoms on the CO2 adsorption. The interaction analyses showed that Li doping enhanced the CO2-framework interaction more distinctively than the N2-framework interaction, leading to an ultra-high CO2 adsorption capacity and CO2/N2 selectivity. Results of this work highlighted Li-β1-GYs as promising materials for CO2/N2 adsorption and separation.

Cellulose acetate based sustainable nanostructured membranes for environmental remediation

Membrane-based gas separation has a great potential for reducing environmentally hazardous carbon dioxide (CO2) gas. The polymeric membranes developed for CO2 capturing have some limitations in their selectivity and permeability. There is a need to overcome these issues and developed such membranes having high-performance CO2 capture with cost-effectiveness. The present study aimed to synthesize mixed matrix membranes (MMMs) having improved properties CO2 adsorption performance and stability than that of pure polymer. Further, the effect on CO2 adsorption by increasing the filler concentration in MMMs was investigated. The MMMs were synthesized by incorporating (1–5 wt%) Cu-MOF-GO composites as filler into cellulose-acetate (CA) polymer matrix by adopting the solution casting method. The performance of MMMs was studied by changing the Cu-MOF-GO composite concentration (1–5 wt%) in the polymer matrix at 45 °C up to 15 bar. Morphological analysis by using SEM confirms that by increasing the concentration of Cu-MOF-GO more than 3% will result in their agglomeration in MMM. The successful incorporation of MOF within the polymer matrix of MMMs was confirmed through the presence of functional groups using FTIR and Raman spectroscopy. XRD analysis revealed that pure CA changes its semi-crystalline behaviour into crystalline by the addition of Cu-MOF-GO. The maximum tensile stress and strain rate of MMMs was 45.1 N/mm2 and 12.8%. In addition, with an increase in (4–5 wt%) Cu-MOF-GO concentration the hydrophilicity of MMMs decreases. The maximum uptake rate of CO2 was 1.79 mmol/g and 7.98 wt% at 15 bar. The adsorption results conclude that Cu-MOF-GO composite and CA-based MMM can be effective for CO2 capture.

Nitrogen Atom-Doped Layered Graphene for High-Performance CO2/N2 Adsorption and Separation

The development of high-performance CO2 capture and separation adsorbents is critical to alleviate the deteriorating environmental issues. Herein, N atom-doped layered graphene (N-MGN) was introduced to form triazine and pyridine as potential CO2 capture and separation adsorbents via regulation of interlayer spacings. Structural analyses showed that accessible surface area of the N-MGN is 2521.72 m2 g−1, the porosity increased from 9.43% to 84.86%. At ultra-low pressure, N-MGN_6.8 have exhibited a high CO2 adsorption capacity of 10.59 mmol/g at 298 K and 0.4 bar. At high pressure, the absolute adsorption capacities of CO2 in N-MGN_17.0 (40.16 mmol g−1) at 7.0 MPa and 298 K are much larger than that of N-doping slit pore. At 298 K and 1.0 bar, the highest selectivity of CO2 over N2 reached up to ~133 in N-MGN_6.8. The research shows that N doping can effectively improve the adsorption and separation capacity of CO2 and N2 in layered graphene, and the interlayer spacing has an important influence on the adsorption capacity of CO2/N2. The adsorption heat and relative concentration curves further confirmed that the layered graphene with an interlayer spacing of 6.8 Å has the best adsorption and separation ability of CO2 and N2 under low pressure. Under high pressure, the layered graphene with the interlayer spacing of 17.0 Å has the best adsorption and separation ability of CO2 and N2.

High-Performance Selective CO2 Capture on a Stable and Flexible Metal-Organic Framework via Discriminatory Gate-Opening Effect.

Selective CO2 capture is of great significance for environmental protection and industrial demand. Here, we report a stable and flexible metal-organic framework (MOF) with excellent water/moisture stability, namely, ZnDatzBdc, that enables high-performance selective CO2 capture from N2 and CH4 via a discriminatory gate-opening effect. ZnDatzBdc shows reversible structural transformation between the open-phase (OP) state and the close-phase (CP) state, owing to the synergistic effect of breakage/re-formation of intraframework hydrogen bonds and the rotation of the phenyl rings. Significantly, ZnDatzBdc exhibits S-shaped isotherms toward CO2, resulting in a large CO2 theoretical working capacity of 94.9 cm3/cm3 under typical pressure vacuum swing adsorption (PVSA) operations, which outperforms other flexible MOFs showing the CO2 selective gate-opening effect except for the miosture-sensitive ELM-11. In addition, CO2 uptake of ZnDatzBdc is well maintained upon multiple water/moisture exposure, indicating its excellent stability. Moreover, ZnDatzBdc establishes remarkable CO2 selectivity with ultrahigh uptake ratios of CO2/N2 (107 at 273 K and 129 at 298 K) and CO2/CH4 (35 at 273 K and 44 at 298 K) at 100 kPa. The in situ gas sorption PXRD experiment verifies that the gate-opening effect takes place in the atmospheric environment of CO2 but not for N2 or CH4. Molecular simulation suggests the selective gate-opening of CO2 comes from its strong electrostatic interactions with the amino groups. Furthermore, effective breakthrough performance and easy regeneration are further confirmed. Hence, combined with excellent separation performance and remarkable stability, ZnDatzBdc can serve as a potential industrial adsorbent for selective CO2 capture.

Precise regulation of CO2 packing pattern in s-block metal doped single-layer covalent organic frameworks for high-performance CO2 capture and separation

The development of high-performance CO2 capture and separation adsorbents is critical to alleviate the deteriorating environmental issues. Herein, six s-block metal doped single-layer polymeric tetraoxa[8]circulene (SBM-TOCs, SBM = Li, Na, K, Be, Mg, and Ca) were introduced as potential CO2 capture and separation adsorbents via precise regulation of CO2 packing patterns. Structural analyses showed that Li-TOC, Na-TOC, K-TOC, and Ca-TOC were screened with high cohesive energies ranging from 7.02 to 7.08 eV/atom and moderate formation energies ranging from –2.92 to –1.41 eV, guaranteeing their structural stabilities for CO2 capture and separation. Electronic structure analyses confirmed the large charge transfer and strong covalent bonding characters between the SBMs and direct-connected O atoms, thus constructing a favorable gas adsorption environment. Li-TOC exhibited an ultrahigh CO2 adsorption capacity of 10.78 mmol/g at 298 K and 1.0 bar, which was superior to previously reported Li-doped adsorbents. At 298 K and 1.0 bar, the selectivity of CO2 over N2/CH4 in Li-TOC reached up to ∼ 516 and ∼ 821, respectively. Polarity regulation analyses showed that SBMs had a more positive effect on the framework affinity for CO2 than N2/CH4 via both coulomb and van der Waals interactions. Space regulation analyses showed that strong interactions between the electropositive SBMs and the electronegative O atoms of CO2 facilitated vertical CO2 configurations and compact distributions, thereby rendering a multilayer CO2 adsorption and enhancing the CO2 adsorption capacity. Results of this work highlighted SBM-TOCs as ultrahigh-performance adsorbents for CO2 capture and separation over N2/CH4, and demonstrated that the precise regulation of CO2 packing pattern was an effective strategy to achieve high-performance gas capture and separation.

Self-activated, urea modified microporous carbon cryogels for high-performance CO2 capture and separation

Conventionally, porous carbons were synthesized using corrosive chemical activating agents. On contrary, we designed a single-step synthesis method for the preparation of a series of self-activated heteroatom (N)-doped carbon cryogels from potassium hydrogen phthalate (KHP) and urea at various temperatures (700–1000 °C), in the absence of any activating agent. To highlight the effectiveness of N-doping in porosity generation and CO2 adsorption/separation, a comparative analysis was drawn with a series of undoped carbon cryogels. Notably, the N-doped cryogels exhibit a highly porous structure with remarkable specific surface area (SSA; 2084 m2 g−1), micropore volume (1.1806 cm3 g−1), well-defined pore size distribution, and abundant narrow micropores (<1.04 nm). Additionally, a considerable mechanical strength (compressive strength = 0.621 MPa and compressive modulus = 8.86 MPa) was also observed. Moreover, the porous cryogel endowed with sufficient pyrrolic nitrogen content (≈51.4 at %) lead to high CO2 adsorption (280.57 mg/g at 273 K and 171.31 mg/g at 298 K at 1 bar) and an excellent ideal adsorbed solution theory (IAST)-based CO2/N2 selectivity (≈115) at 273 K, surpassing the CO2 adsorption/separation performance of previously reported N-doped carbons and resorcinol-based carbon gels. Furthermore, the moderate heat of adsorption (36.109 kJ mol−1) and stable cyclic behavior of CO2 adsorption-desorption under flue gas conditions (i.e., 15% CO2/85% N2) unveils the physisorption nature of adsorption which governs the energy-effective regeneration process. Summarizing, the present work demonstrates the successful fabrication of highly porous carbon cryogels as efficient CO2 adsorbents, thereby opening new synthetic avenues for self-activating porous carbon formation.

Elucidating the transition between CO2 physisorption and chemisorption in 1,2,4-triazolate ionic liquids at a molecular level

Capture of CO2 is a crucial process to achieve carbon neutrality. High-performance CO2 capture involves both physi- and chemi-sorption, with a transition between them. However, the underlying mechanistic insights required to produce the methods to tune the transition are poorly understood. Here, we describe a series of 1,2,4-triazolate ionic liquids (TZ ILs) that capture > 0.7 mol CO2/mol TZ IL in a two-stage absorption process. Physi- and chemi-sorption were studied by spectroscopy using 13CO2 and the transition between the two sorption modes has been identified. UV–Vis, FT-IR and NMR spectroscopy as well as density and viscosity measurements demonstrate that physisorption is initially the dominant process whereas later chemisorption predominates. Based on the identification of key species combined with theoretical modelling, a plausible molecular-level mechanism is proposed for the transition between the two sorption modes. These mechanistic insights enable the transition of CO2 capture to be tuned.

Phytic acid-induced self-assembled chitosan gel-derived N, P–co-doped porous carbon for high-performance CO2 capture and supercapacitor

Heteroatom-doped porous carbon materials (HPCMs) have attracted great attention due to their excellent physical and chemical properties and the enhanced performance of multiple heteroatom co-doping. Herein, N, P-co-doped porous carbon materials (NPPCs) are developed via a novel synthesis of the phytic acid-induced self-assembled chitosan aerogel followed by pyrolysis and activation. Phytic acid serves as a P source, acid regulator and structure-directing agent for improved activation efficiency to create more pores. A little of NaNO 3 is used both as a template and activator simultaneously. The porosity and N content of such NPPCs are controlled by rationally tuning the pyrolysis temperature and the mount of NaNO 3 . The NPPC-0.75-600 delivers a good CO 2 adsorption capability of 3.02 and 5.31 mmol g −1 at 100 and 500 kPa, respectively, and has an excellent stability with almost no adsorption capacity decay even after successive 20 cycles. For supercapacitors (SCs), the NPPC-0.75-700 also displays a high capacitance of 231.2 F g −1 at 1 A g −1 and an outstanding stability at circa 96.7% initial capacity after 10000 cycles. These results highlight the great potential of such NPPCs in CO 2 capture and SCs, and the novel synthetical route offers new insights for the readily scalable production of HPCMs. • Phytic acid induced chitosan gel and served as a P source and activation agent. • N,P-co-doped porous carbon delivered a CO 2 capture ability of 5.31 mmol g −1 at 298 K. • N,P-co-doped porous carbon exhibited specific capacitance at 231.2 F g −1 at 1 A g −1 . • CO 2 capture and supercapacitor performances were substantially improved by P doping.

Li-Decorated Β1-Graphyne for High-Performance Co2 Capture and Separation Over N2

Li-Decorated Β1-Graphyne for High-Performance Co2 Capture and Separation Over N2

In-situ formation of asymmetric thin-film, mixed-matrix membranes with ZIF-8 in dual-functional imidazole-based comb copolymer for high-performance CO2 capture

Despite numerous studies on free-standing, mixed-matrix membranes (MMMs), the development of thin-film MMMs with high permeance is still an ongoing challenge. Here, the successful fabrication of ultra-high-permeance thin-film MMMs on a porous polymer substrate is described based on a highly porous zeolitic imidazole framework (ZIF-8) and a dual-functional imidazole-based comb copolymer. The copolymer of poly(vinyl imidazole)-poly(oxyethylene methacrylate) (PVI-POEM) is synthesized via free-radical polymerization, and it exhibits CO2-philicity, strong adhesion, and good interactions with fillers. In contrast to commercial benchmark membranes such as Pebax, the use of the PVI-POEM comb copolymer results in significant improvement in the CO2 permeance without significant loss of selectivity even at high ZIF-8 loadings and low thickness. It is attributed to the in-situ formation of inverse, asymmetric morphology of MMMs and partial infiltration of PVI-POEM chains into ZIF-8 particles. Optimization of the preparation process, such as ZIF-8 loading, substrate type, and coating layer thickness, leads to an extremely high CO2 permeance of 4474 GPU with high CO2/N2 and CO2/CH4 ideal selectivities of 32.0 and 12.4, respectively, which is far beyond the current trade-off limit for membranes. The mechanism behind the exceptionally high CO2 separation performance is delineated by exploring molecular dynamic simulation through morphology, structural, and energetic analyses.

Amino-functionalized ZIFs-based porous liquids with low viscosity for efficient low-pressure CO2 capture and CO2/N2 separation

Construct permanent porosity into liquids remains challenging, such as preparation, lower viscosity, economical, high-performance gas sorption, and separation. Herein, a general and economical surface engineering strategy has been implemented to construct a novel type Ⅰ porous liquids based on zeolitic imidazolate frameworks (denoted as ZIFs-based PLs) via covalently linking of amino-functionalized ZIFs with the diglycidyl ether-terminated of PDMS. The properties including free pore volume, viscosity, melting temperature (Tm), the gas capture, and CO2/N2 selective separation performance of PLs can be regulated by adjusting the pore structures, the amount of –NH2 introduced into ZIFs and molecular weight of the outer layers of PDMS, etc. Particularly, PLs1(1000)-5%, and PLs2(1000)-5% present viscosity values with 49 mPa⋅S-1 and 59 mPa⋅S-1 at 25 °C, to our best knowledge, which is the lowest viscosity of type I PLs reported previously. Meanwhile, Tm of PLs broke down to −78 °C, showing a wide liquid range. Remarkably, type Ⅰ PLs1(14000)-15.5% exhibits approximately 10 times higher CO2 uptake than that of the polymer in outer layers, which is attributed to the permanent free volume of ZIFs, chemistry sorption, and excellent liquidity. The CO2 breakthrough time of PLs for the CO2/N2 mixture was delayed for 53.7 s, confirming that PLs exhibits efficient CO2/N2 separation performance. Therefore, we envision that such a general and economical strategy will open new insights to construct innovative low viscosity type Ⅰ PLs with high-performance CO2 capture and CO2/N2 separation at low pressure.

High performance CO2 capture at elevated temperatures by using cenospheres prepared from solid waste, fly ash

Cenospheres (CS) are spherical shaped inorganic frameworks present in with fly ash which is generated from coal-fired thermal power plants. These spherical structures were functionalized with imidazole and amine moieties to capture CO2 selectively from flue gases at elevated temperature. The functionalized CS have shown a high selectivity for CO2 adsorption (4.68 mmol g−1) over N2 (0.46 mmol g−1) at 333 K/1 bar from a simulated flue gas (0.15 CO2 and 0.85 N2, v%) composition of thermal power plants. When the moisture content reached to 30 vol% the adsorption capacity of CS materials was reduced to 20 vol% as compared to dry flue gas. The functionalized CS can be used repeatedly for 50 cycles without losing its adsorption capacity. The cost estimate for CO2 capture by using the proposed adsorption system would be $12.01/ton of CO2 which is lower as compared to amine absorption system and zeolite-based adsorption system reported in the literature. The CS materials are prepared from solid wastes reduce the cost of production and their large scale manufacturing is technically feasible to capture CO2 from industrial flue gases efficiently in near future.

Hierarchical porous N-doped carbon xerogels for high performance CO2 capture and supercapacitor

Novel microporous carbon xerogels (CX-HMTAs) with different morphologies and well-developed porosity were successfully fabricated. The hierarchical pore, surface structure, and nitrogen content could be easily controlled by adjusting the amount of hexamethylenetetramine (HMTA). The samples as-obtained exhibited high micropore volume and large specific surface area, which were applied as supercapacitor electrodes and CO2 capture materials. The CX-HMTA4 with a moderate concentration of HMTA (0.72 %) afforded the highest CO2 adsorption capability with 4.21 mmol g−1 at 273 K and 1 bar, and excellent ideal adsorption solution theory (IAST) selectivity with 70 for CO2/N2 capture at 298 K. Moreover, the CX-HMTA4 were simultaneously conducted as a supercapacitor electrode, and gave a maximum specific capacitance of 161 F g-1 and high stability (retained 99.4 % capacity after 1000 cycles) in 6 M KOH electrolyte at 1 A g-1, showed a great advance when compared with most reported benchmark carbon materials. The multifunctional porous carbon materials presented herein were facilely prepared without any activation, exhibiting considerable potentials for large-scale gas adsorption/separation and electrochemical energy storage.

Meso/Microporous Carbons from Conjugated Hyper-Crosslinked Polymers Based on Tetraphenylethene for High-Performance CO2 Capture and Supercapacitor.

In this study, we successfully synthesized two types of meso/microporous carbon materials through the carbonization and potassium hydroxide (KOH) activation for two different kinds of hyper-crosslinked polymers of TPE-CPOP1 and TPE-CPOP2, which were synthesized by using Friedel–Crafts reaction of tetraphenylethene (TPE) monomer with or without cyanuric chloride in the presence of AlCl3 as a catalyst. The resultant porous carbon materials exhibited the high specific area (up to 1100 m2 g−1), total pore volume, good thermal stability, and amorphous character based on thermogravimetric (TGA), N2 adsoprtion/desorption, and powder X-ray diffraction (PXRD) analyses. The as-prepared TPE-CPOP1 after thermal treatment at 800 °C (TPE-CPOP1-800) displayed excellent CO2 uptake performance (1.74 mmol g−1 at 298 K and 3.19 mmol g−1 at 273 K). Furthermore, this material possesses a high specific capacitance of 453 F g−1 at 5 mV s−1 comparable to others porous carbon materials with excellent columbic efficiencies for 10,000 cycle at 20 A g−1.