Outstanding CO2 Research Articles

An active and Cr-tolerant high-entropy La0.7Sr0.3FeO3-δ based cathode for solid oxide fuel cells

The development of high active and stable cathode materials is one of the main challenges of intermediate temperature solid oxide fuel cells (SOFCs). Herein, a high-entropy Fe-based perovskite oxide La0.7Sr0.3Fe0.3Ni0.3Co0.3Mo0.1O3-δ (LSFNCM) is synthesized by self-propagation combustion based on La0.7Sr0.3FeO3-δ (LSF) and the electrochemical properties are systematically tested. The symmetric half-cell with the LSFNCM cathode has a high catalytic activity with a polarization impedance of 0.12 Ω·cm2 at 800 °C, and also shows outstanding CO2 resistance and chromium resistance owing to the entropy stabilization strategy. After 50h of treatment in a 10% CO2 environment, the polarization impedance of the LSF electrode increases by 8.89 Ω·cm2, while that of the LSFNCM electrode only increases by 1.81 Ω·cm2. Additionally, after being treated for 24h in a chromium vapor environment, the polarization impedance of the LSF electrode increases by 5.95 Ω·cm2, whereas that of the LSFNCM electrode only increases by 0.44 Ω·cm2. Moreover, the single cell with LSFNCM cathode exhibits the maximum power density of 932.82 mW/cm2 and the polarization impedance of 0.34 Ω·cm2 at 800 °C with humidify hydrogen as fuel. Our results indicate that high-entropy perovskite oxide LSFNCM is an active and Cr-tolerant promising cathode for SOFCs.

Ru Single Atom Dispersed Cu Nanoparticle with Dual Sites Enables Outstanding Photocatalytic CO2 Reduction.

Cu-based catalysts are promising candidates for CO2 reduction owing to the favorable energetics of Cu sites for CO2 adsorption and transformation. However, CO2 reduction involving insurmountable activation barriers and various byproducts remains a significant challenge to achieve high activity and selectivity. Herein, a photocatalyst constructed with single-Ru-site-on-Cu-nanoparticle on Bi4Ti3O12 exhibits exceptional activity and selectivity for CO2 conversion to CO. The experimental and theoretical results consistently reveal that the Ru-Cu dual sites allow the rapid transfer of photogenerated carriers for closely interacting with CO2 molecules. Importantly, the Ru-Cu dual sites exhibit extremely strong CO2 adsorption ability, and the Gibbs free energy of the rate-determining step (*CO2 to *COOH) has been significantly reduced, synergistically enhancing the entire CO2 conversion process. The optimal BTOCu2Ru0.5 photocatalyst manifests a high performance for selective reduction of CO2 to CO, yielding 10.84 μmol over 15 mg of photocatalyst in 4 h (180.67 μmol·g-1·h-1) under a 300 W Xe lamp without any photosensitizer and sacrificial reagent, outperforming all bismuth-based materials and being one of the best photocatalysts ever reported under similar reaction conditions. This work presents a strategy for the rational design of multiple metal sites toward efficient photocatalytic reduction of CO2.

A C-modified engineering strategy of porous In2O3 catalysts for point-concentrated solar-driven photothermal CO2 hydrogenation

The solar-driven photothermal CO2 conversion serves as an effective approach for addressing the substantial challenges of energy crises and global environmental issues. In this work, various forms of In2O3 catalysts, including In2O3-c, In2O3-r, In2O3-s, and porous spherical In2O3, along with a C-modified porous spherical In2O3 catalyst (C-In2O3), were successfully synthesized through a hydrothermal method. An in-depth analysis was conducted to evaluate the performance of these catalysts in the point-concentrated solar-driven photothermal CO2 hydrogenation. As a result, the porous C-In2O3 catalyst exhibited a superior CO2 conversion rate of approximately 13.2 % under simulated sunlight irradiation, with a light intensity of 44.6 mW/cm2. Notably, all catalysts demonstrated nearly 100 % selectivity towards CO (CO production rate of around 8.51 mmol gcat−1h−1) during the photothermal catalytic reaction, without any formation of CH4. The outstanding performance of the C-In2O3 catalyst was attributed to the modification of In2O3 band structure by the incorporation of C, which significantly enhanced the intensive solar light absorption of the catalyst. Furthermore, incorporating C into In2O3 substantially augments its basic strength and significantly elevates the quantity of basic sites, thereby endowing it with outstanding CO2 adsorption and conversion capabilities. This work provides a C-modified engineering strategy to design efficient photothermal catalysts for boosting point-concentrated photothermal CO2 hydrogenation.

Photoreduction of carbon dioxide into methane and ethylene using TiO2 inverse opal-derived PCN-222(M)

Solar-driven photocatalytic CO2 reduction has significant potential to address the energy crisis and mitigate greenhouse gas emissions by producing valuable organic compounds. Narrow bandgap materials enhance photon absorption within the visible light spectrum, thereby improving exciton generation. Both the inverse opal (IOT) and the porphyrin-based MOF (PCN-222) exhibit biomimetic design concepts. The IOT has a highly ordered porous structure that increases the light-absorbing surface area, facilitating efficient light harvesting. Conversely, the PCN-222 structure, which is modelled on biological porphyrin molecules, has a highly ordered pore structure and abundant active centers. Under hydrothermal conditions, PCN-222 self-assembles on the IOT surface to form a P(Cu, Fe, Zn)/IOT heterostructure. The tight interface of this heterostructure promotes rapid electron-hole separation and transport. In addition, the slow-light effect is exploited to increase the light absorption efficiency, thus improving the overall photocatalytic reaction efficiency and stability. In this study, the morphology, structure and photoelectric properties of P(Cu, Fe, Zn)/IOT heterostructures are investigated, revealing enhanced photocatalytic efficiency. The P(Fe)/IOT composite demonstrated outstanding CO2 conversion rates under simulated sunlight, yielding carbon monoxide (62 %), methane (0.11 %), and ethylene (0.09 %). The Z-scheme charge transfer mechanism significantly enhances photocatalytic performance by improving the efficiency of carrier separation and transfer, thereby increasing the overall photocatalytic reaction efficiency. This advance offers significant benefits for environmental and renewable energy remediation. The study provides key insights and recommendations for enhancing the efficiency of Z-scheme photocatalytic systems in future research and development.

Synthesis and characterization of porous silica and composite films for enhanced CO₂ adsorption: A circular economy approach

This study explores the synthesis and application of carbon-negative technology that leverage circular economy and environmentally friendly methodologies. Porous silica using plant-derived silica sources and self-assembled lignin templates were prepared, achieving an impresive surface area of up to 104.76 m2/g. Additionally, we prepared porous composite films via a freeze-drying process incorporating polyvinyl alcohol (PVA). These films demonstrated enhanced tensile properties, with a tensile strength reaching 285.72 kPa. Notably, the film surfaces engaged in a third-body tribology mechanism, which endowed them with excellent abrasion resistance and a low friction coefficient. The specific surface area of the films was measured at 20.15 m2/g, making them ideal substrates for CO₂ adsorption functionalization. The functionalized films showcased outstanding CO₂ adsorption capabilities, with a maximum uptake of 29.38 mg/g. Furthermore, they retained over 90% of their adsorption capacity after five adsorption/desorption cycles. Under high CO₂ conditions, these composite films combine the desirable attributes of both solid and liquid adsorbents—high surface area, low volatility, and adsorption stability—contributing significantly to greenhouse gas mitigation and the pursuit of carbon neutrality.

Efficient CO2 removal enabled by N, S co-doped hierarchical porous carbon derived from sustainable lignin

Biomass-derived heteroatoms-doped hierarchical porous carbon materials are highly regarded as promising CO2 adsorbents. However, these materials cannot simultaneously exhibit advanced porosity, high yield, and high heteroatom content. Herein, a series of N, S co-doped hierarchical porous carbons with advanced porosity (narrow micropore: 0.37–0.42 cm3/g), high heteroatom content (N content: 8.54 at% and 8.87 wt% and S content: 0.86 at% and 1.73 wt%) and remarkable yield (57.12–69.13 wt%) was produced using lignin as the raw material via a synergistic strategy involving melamine modification and CuCl2 activation. Notably, melamine modification not only introduced mesopores, but also promoted the effect of CuCl2 activation to generate additional micropores. Importantly, the advanced porosity required a low dosage of CuCl2. The optimized adsorbent (NHPC-850) exhibits outstanding CO2 adsorption capacity (6.87 mmol/g at 273 K and 100 kPa, 3.57 mmol/g at 303 K and 100 kPa), a moderately high heat of adsorption (34.7 kJ/mol), and an extraordinary CO2/N2 selectivity (132 at 273 K/81 at 303 K). These excellent properties are attributed to the well-developed micropores and suitable mesopores of carbon materials, as well as rich nitrogen and sulfur functionality in the carbon structure. Collectively, this work offers new insights into a simple and easy-to-scale strategy for the preparation of biomass-derived N, S co-doped hierarchical porous carbon.

Turning copper into an efficient and stable CO evolution catalyst beyond noble metals

Using renewable electricity to convert CO2 into CO offers a sustainable route to produce a versatile intermediate to synthesize various chemicals and fuels. For economic CO2-to-CO conversion at scale, however, there exists a trade-off between selectivity and activity, necessitating the delicate design of efficient catalysts to hit the sweet spot. We demonstrate here that copper co-alloyed with isolated antimony and palladium atoms can efficiently activate and convert CO2 molecules into CO. This trimetallic single-atom alloy catalyst (Cu92Sb5Pd3) achieves an outstanding CO selectivity of 100% (±1.5%) at −402 mA cm−2 and a high activity up to −1 A cm−2 in a neutral electrolyte, surpassing numerous state-of-the-art noble metal catalysts. Moreover, it exhibits long-term stability over 528 h at −100 mA cm−2 with an FECO above 95%. Operando spectroscopy and theoretical simulation provide explicit evidence for the charge redistribution between Sb/Pd additions and Cu base, demonstrating that Sb and Pd single atoms synergistically shift the electronic structure of Cu for CO production and suppress hydrogen evolution. Additionally, the collaborative interactions enhance the overall stability of the catalyst. These results showcase that Sb/Pd-doped Cu can steadily carry out efficient CO2 electrolysis under mild conditions, challenging the monopoly of noble metals in large-scale CO2-to-CO conversion.

Oxygen vacancy-mediated Mn2O3 catalyst with high efficiency and stability for toluene oxidation

Oxygen vacancy engineering in transition metal oxides is an effective strategy for improving catalytic performance. Herein, defect-enriched Mn2O3 catalysts were constructed by controlling the calcination temperature. The high content of oxygen vacancies and accompanying Mn4+ ions were generated in Mn2O3 catalysts calcined at low temperature, which could greatly improve the low-temperature reducibility and migration of surface oxygen species. DFT theoretical calculations further confirmed that molecular oxygen and toluene were easily adsorbed over defective α-Mn2O3 (222) facets with an energy of −0.29 and −0.48 eV, respectively, and corresponding OO bond length is stretched to 1.43 Å, resulting in the highly reactive oxygen species. Mn2O3-300 catalyst with abundant oxygen vacancies exhibited the highest specific reaction rate and lowest activation energy. Furthermore, the optimized catalyst possessed the outstanding stability, water tolerance and CO2 yield. In comparison with the fresh Mn2O3-300 catalyst, the physical structure and surface property of the used catalyst remained almost unchanged regardless of whether undergoing the stability test at consecutive catalytic runs as well as high temperature, and water resistance test. In situ DRIFTS spectra further elucidated that introducing the water vapor had little effect on the reaction intermediates, indicating the excellent durability of the defect-enriched catalyst.

Synthesis of customized zeolite X with outstanding CO2 selectivity over CH4 and N2 using facile activated spent fluid catalytic cracking catalysts

Efficient separation of CO2 from natural gas mixtures (CO2/CH4) and flue gas (CO2/N2) is pivotal for effective carbon capture and sequestration. Utilizing adsorbents derived from solid waste provides additional benefit for the carbon capture industry. This study introduces a convenient activation method at 200 °C for SFCC. Utilizing the activated SFCC as raw material under mild hydrothermal conditions, highly crystalline zeolite X (referred to as SFCC-X-200) of commercial quality with exceptional CO2 separation ability from CH4 and N2 is obtained. The static water adsorption rate of SFCC-X-200 meets the requirements of the national standard for commercial zeolite X (GB6287-86). Moreover, the ideal adsorbed solution theory (IAST) selectivity of SFCC-X-200 for CO2 from CO2/N2 (15/85, v/v) and CO2/CH4 (50/50, v/v) mixtures is significantly higher, at 797 and 199, respectively, compared to commercial X zeolite. SFCC-X-200 demonstrates tremendous potential for separating CO2/N2 and CO2/CH4 mixtures due to its outstanding adsorption capacity and selectivity, rapid attainment of adsorption equilibrium, complete desorption at ambient temperature, and extremely low cost.

PIM-1-assisted structuring of amine-functionalized porous organic copolymer for post-combustion carbon dioxide capture

Capturing CO2 from flue gas of coal-burned power plants has been considered to be a promising technology to mitigate the environmental problems caused by rising level of CO2 at the atmosphere. Amine-functionalized adsorbents, showing impressive CO2 adsorption capability and selectivity even at low CO2 partial pressure, face the challenge of permanent structural changes and performance deterioration due to the irreversibly bonding of SO2, a common impurity of flue gas, particularly under humid condition. Besides, the reported amine-functionalized adsorbents are usually nano-sized powders, impractical for industrial applications. Therefore, the development of efficient, stable, and structured CO2 adsorbents is still an urgent need. Herein, we develop a novel structured mixed-matrix adsorbent (PIM-PP-DETA), using a diethylenediamine-appended porous organic copolymer (PP-DETA, prepared by a copolymerization reaction of dichloro-p-xylene and 4,4′-bis(chloromethyl)biphenyl and a one-step amine grafting process) as main adsorbent and PIM-1 as polymer matrix through a phase inversion process. The as-developed PIM-PP-DETA not only exhibits high CO2 adsorption capacity and outstanding CO2 selectivity over N2, but also shows fast adsorption kinetics and high stability under repeated adsorption-desorption cycling under dynamic flow conditions. Furthermore, PIM-PP-DETA possesses high tolerance towards acidic and moist environments, with CO2 adsorption capacity remained at a relatively high level after SO2 and humid exposure, suggesting its potential usage to post-combustion CO2 capture.

Highly oxygen reduction activity and CO2 resistance of Fe-based cathode electrocatalysts for solid oxide fuel cells

The insufficient electrocatalytic activity and CO2 resistance hinder the application of cathode material for solid oxide fuel cells (SOFCs). In this study, we introduce a series of Pr-doped perovskite Bi0.8–xPrxCa0.2FeO3–δ (BPCFx, x=0, 0.10, 0.15, 0.20) as candidate cathode materials, with a focus on its phase structure, oxygen desorption ability, catalytic activity, and electrochemical reduction kinetics. Among all the components, the Bi0.6Pr0.2Ca0.2FeO3–δ (BPCF0.20) catalyst shows impressive oxygen reduction reaction (ORR) activity, with a low polarization resistance of 0.06 Ω cm2 at 700 °C and peak power density of 810 mW cm−2 at 800 °C. Moreover, the BPCF0.20 cathode shows outstanding CO2 resistance in different CO2 concentrations (1%–10%) due to the larger average bond energy and higher relative acidity of Bi, Pr, and Fe ions. These findings demonstrate that BPCFx are advanced cathode electrocatalysts for SOFCs.

Improving physical properties, microstructure and actual carbon sequestration of steel slag based autoclaved aerated concrete by accelerated carbonation

This study presents an autoclaved aerated concrete (AAC) with steel slag (SS) as carbonate-able binder. The traditional autoclaving process was augmented with a carbonation stage to improve the physical properties, microstructure and actual carbon sequestration of steel slag based autoclaved aerated concrete (SS-AAC). The macroscopic and microscopic test results showed that the carbonation process stimulated the reactivity of SS to generate gel products, allowing the additional formation of tobermorite during the autoclaving process. Under the synergistic positive effect of the densification-induced micro-pore refinement caused by calcium carbonate precipitation and the excellent gas permeability of AAC, the intervention of carbonation process resulted in SS-AAC with higher compressive strength, more homogeneous carbonation, and more outstanding actual CO2 absorption efficiency. The research provides a potential method for preparing high-volume solid waste AAC with large-scale CO2 utilization to encourage the concrete sector to adopt a sustainable stance.

Co–N–C anchored g-C3N4 plate enhancing surface activity for efficient visible-light photocatalytic rhodamine-B elimination and CO2 conversion

Poor light-harvesting, fast recombination of photo-induced charge carriers, and unfavorable surface adsorption remain the major issues restricting the photocatalytic activity of g-C3N4. In this study, the Co-N-C decorated g-C3N4 (Co-N-C/g-CN) plate was developed by constructing Co-N-C on the surface of g-CN plate to improve photocatalytic rhodamine-B (RhB) degradation and CO2 conversion. The as-prepared 0.5Co-N-C/g-CN plate exhibited an exceptionally high efficiency in photocatalytic RhB degradation, with a rate of 99.5 % achieved in mere 30 min. Besides, the 0.5Co-N-C/g-CN plate also demonstrated an outstanding photocatalytic CO2 conversion rate of 33.7 μmol g−1cat h−1 within 4 h, which was more than 3.4-fold that of g-CN (9.9 μmol g−1cat h−1). Experiments demonstrated that the surface-constructed Co-N-C enhanced the visible light-harvesting and the separation of photo-induced charge carriers, boosting the optical property. Moreover, the density functionalized theory (DFT) calculations verified that the Co-N-C cocatalyst optimized O2 adsorption for the generation of superoxide radicals (·O-2), accelerating the photocatalytic RhB removal. Meanwhile, the Co-N-C was advantageous for the adsorption and activation of CO2, facilitating the photocatalytic CO2 conversion. This study provides a perspective on the surface engineering of g-CN toward enhanced photocatalytic performance.

MXenes as Electrocatalysts for Energy Conversion Applications: Advances and Prospects

Hydrogen as a potential future energy source provides a number of benefits in terms of sustainability, high energy density, and zero emissions. The production of hydrogen via water splitting is regarded as the cleanest and sustainable process. In contrast, fossil fuel combustion causes significant environmental problems through the production and release of secondary gases such as NOx, SO2, and CO2. It is vital to focus on reducing these harmful gases. CO2, a major pollutant produced by the combustion of fossil fuels and various human activities, plays a central role in the greenhouse effect and contributes to global warming. It is therefore imperative to actively eliminate and mitigate CO2 levels to preserve the global environment. MXenes and MXene‐based catalysts exhibit both outstanding hydrogen evolution reaction (HER) performance and CO2 reduction. In this review, recent progress is systematically examined and discussed in the preparation and utilization of MXenes as catalysts for HER and carbon dioxide reduction reaction (CO2RR). The discussion begins with a concise overview of the fabrication and characteristics of MXenes, followed by a comprehensive exploration of their efficacy as catalysts for HER and CO2RR.

Quaternized Graphene for High-Performance Moisture Swing Direct Air Capture of CO2.

Nowadays, moisture-swing adsorption technology still relies on quaternary ammonium resins with limited CO2 capacity under ambient air conditions. In this work, a groundbreaking moisture-driven sorbent is developed starting from commercial graphene flakes and using glycidyltrimethylammonium chloride for incorporation of CO2-sensitive quaternary ammonium functional groups. Boasting an outstanding CO2 capture performance under ultra-diluted conditions (namely, 3.24mmolg-1 at CO2 400ppm and 20% RH), the functionalized sorbent (fGO) features clear competitive advantages over current technologies for direct air capture. Notably, fGO demonstrated unprecedented moisture-swing capacity, ease of regenerability, versatility, selectivity, and longevity. These distinctive features position the fGO as an advanced and promising solution, showcasing its potential to outperform existing methods for moisture-swing direct air capture of CO2.

High-Entropy Oxides: A New Frontier in Photocatalytic CO2 Hydrogenation.

Herein, we investigate the potential of nanostructured high-entropy oxides (HEOs) for photocatalytic CO2 hydrogenation, a process with significant implications for environmental sustainability and energy production. Several cerium-oxide-based rare-earth HEOs with fluorite structures were prepared for UV-light driven photocatalytic CO2 hydrogenation toward valuable fuels and petrochemical precursors. The cationic composition profoundly influences the selectivity and activity of the HEOs, where the Ce0.2Zr0.2La0.2Nd0.2Sm0.2O2-δ catalyst showed outstanding CO2 activation (14.4 molCO kgcat-1 h-1 and 1.27 kgcat-1 h-1) and high methanol and CO selectivity (7.84% CH3OH and 89.26% CO) under ambient conditions with 4 times better performance in comparison to pristine CeO2. Systematic tests showed the effect of a high-entropy system compared to midentropy oxides. XPS, in situ DRIFTS, as well as DFT calculation elucidate the synergistic impact of Ce, Zr, La, Nd, and Sm, resulting in an optimal Ce3+/Ce4+ ratio. The observed formate-routed mechanism and a surface with high affinity to CO2 reduction offer insights into the photocatalytic enhancement. While our findings lay a solid foundation, further research is needed to optimize these catalysts and expand their applications.

Selective Photocatalytic CO2 Reduction Through Plasmonic Z‐Scheme Ag‐Bi2O3‐ZnO Heterostructures

AbstractCombination of plasmonic noble metal with semiconductors offers a promising and potential solar energy harvesting and conversion route. Herein, plasmonic Z‐scheme Ag‐Bi2O3‐ZnO (AgBZ) heterostructure is designed and synthesized via solution combustion and photo‐deposition method. Metallic Ag nanoparticles (NPs) were deposited over Bi2O3‐ZnO heterostructure; thus, they exhibit strong visible light absorption owing to surface plasmon resonance (SPR). The photocatalytic efficiency of the synthesized catalysts is investigated by the photocatalytic CO2 reduction to fuels under simulated solar light irradiation. The present system has shown an outstanding photocatalytic CO2 reduction and excellent selectivity of CO. The evolved rate of CO fuel, the amount of CO produced per unit time, over optimized Ag‐Bi2O3‐ZnO (3AgBZ) heterostructures was (96.74 μmol g−1/h) which was approximately 12 times larger than that of Bi2O3‐ZnO (0AgBZ) and 49‐fold than the quantity of evolved CO fuels over pure ZnO photocatalyst. The percentage of evolved CO to CH4 fuels over optimized Ag‐Bi2O3‐ZnO (3AgBZ) heterostructures was about 50 : 1compared to that of 2 : 3 over Bi2O3‐ZnO (0AgBZ). The great improvement and the high selectivity would be ascribed to the synergistic effect of metallic surface plasmon resonance and the Z‐scheme charges transfer system. This work would open a window to construct a single photocatalyst with different charge separation systems and excellent CO2 reduction selectivity. Finally, the mechanism for the enhanced photocatalytic performance by the synergistic effect was described and discussed.

Engineering Built-In Electric Field Microenvironment of CQDs/g-C3N4 Heterojunction for Efficient Photocatalytic CO2 Reduction.

Graphitic carbon nitride (CN), as a nonmetallic photocatalyst, has gained considerable attention for its cost-effectiveness and environmentally friendly nature in catalyzing solar-driven CO2 conversion into valuable products. However, the photocatalytic efficiency of CO2 reduction with CN remains low, accompanied by challenges in achieving desirable product selectivity. To address these limitations, a two-step hydrothermal-calcination tandem synthesis strategy is presented, introducing carbon quantum dots (CQDs) into CN and forming ultra-thin CQD/CN nanosheets. The integration of CQDs induces a distinct work function with CN, creating a robust interface electric field after the combination. This electric field facilitates the accumulation of photoelectrons in the CQDs region, providing an abundant source of reduced electrons for the photocatalytic process. Remarkably, the CQD/CN nanosheets exhibit an average CO yield of 120µmol g-1, showcasing an outstanding CO selectivity of 92.8%. The discovery in the work not only presents an innovative pathway for the development of high-performance photocatalysts grounded in non-metallic CN materials employing CQDs but also opens new avenues for versatile application prospects in environmental protection and sustainable cleaning energy.

Preparation and CO2 adsorption behavior of ZIF-67-based porous liquids: A molecular dynamics study

Porous liquids (PLs) are fluids with permanent intramolecular pores, which showed high potential in CO2 capture. In this paper, novel Metal-organic Framework (MOF)-based PL has great porosity and abundant adsorption sites, achieving outstanding CO2 adsorption capacity were constructed using ZIF-67 and 18-crown-6 as dispersant. The physicochemical properties and mechanisms were studied by combining molecular dynamics simulations and quantitative calculations. ZIF-67 could be uniformly dispersed in 18-crown-6 through weak interactions, the compound has good fluidity, containing stable CO2 transmission channels and storage pores, endowing it with a high CO2 adsorption capacity than existing porous liquids. The adsorption of CO2 in ZIF-67/18-crown-6 PL is a physical adsorption through van der Waals interaction, and the recycling of the PL can be achieved by adjusting temperature and pressure. It was extra valuable that the fluidity performance of ZIF-67/18-crown-6 PL was confirmed through experimental characterizations. This work not only provides a novel PL system to achieve CO2 capture, but also gives out a new approach for the development of MOF-based functional materials.

Nanoporous Ti3C2O2 monolayer towards high permeance and selectivity for CO2/N2 separation: CO2-MXene interaction tuning

MXene, as a new gas separation membrane, has good stability and suitable pore topological structures to mitigate the greenhouse effect caused by excessive CO2 emission. However, the large quadrupole and polarizability of CO2 make it a strong interaction with MXene, thus leading to a strong solubility and weak diffusivity of CO2. Here, we design nanoporous Ti3C2O2 monolayers (YmXn) with exposed C atoms that could tune CO2-Ti3C2O2 interaction so as to improve gas separation performance by density functional theory and molecular dynamics simulation. The scope of “Cut-off” size is obtained by analyzing the gas separation state from un-permeation to permeation. Results reveal that nanoporous Ti3C2O2 membranes achieve both outstanding CO2 selectivity and permeance. The best-performance Y3X3-Ti possesses CO2 permeance of 1.01 × 10-4 and 2.56 × 10-5 mol s−1 m−2 Pa−1 for equimolar gas mixtures and flue gases, respectively, and both the CO2/N2 selectivity reach 100 %. The gas separation mechanism is dominated by diffusion selectivity rather than solution selectivity in nanoporous Ti3C2O2. The dynamic processes of gas permeation, including the center of mass, mean square displacement, and radial distribution function of the gases, are precisely investigated. The electrostatic repulsion between the C atoms in the channel of the membrane and CO2 follows the sequence Y3X3-C > Y2X4 > Y3X3-Ti, which is the key to regulating gas diffusion. Results of this work highlight that tuning gas-membrane interaction and designing “Cut-off” size are effective strategies to achieve excellent CO2 separation performance, and shed new light on the intrinsic mechanism in high-performance gas separation membranes.