CO2 Uptake Research Articles

Molecular sieves hybrid metal–organic framework for efficient simultaneously capturing carbon dioxide and collecting water from air

Water scarcity and climate change associated with global warming are two common challenges facing humankind. The simultaneous removal of water and carbon dioxide (CO2) from the air has become a popular candidate strategy to address these challenges. In this paper, molecular sieve@MOF composites were synthesized in-situ for the first time by adding ZSM-5 and HZSM-5 during the preparation of Mg/DOBDC. A comprehensive review of the air capture CO2 and water harvesting properties of the novel composites was also presented. Primarily, the effects of molecular sieve category and ratio on the composite were systematically investigated. Subsequently, the crystal structure, morphological composition and textural properties of the composites were characterized. Finally, CO2/H2O co-adsorption performance, adsorption and desorption cycle stability and adsorption mechanism were investigated. The results demonstrated that the metal nodes of Mg/DOBDC interacted with the molecular sieve surface functional groups to increase the metal active sites and porosity. The obtained 0.5HZSM-5@Mg/DOBDC MOF showed the maximum CO2 uptake of 15.90 mmol/g (0.1 MPa, 25 °C), which was 3.66 times the amount of Mg/DOBDC.

Unveiling the porosity effect of superbase ionic liquid-modified carbon sorbents in CO2 capture from air

Direct air capture (DAC) of CO2 represents one of the most promising technologies to achieve negative carbon emissions. In this work, the superbase ionic liquids (ILs)-modified carbon substrates were developed for DAC of CO2 by harnessing the strong CO2 binding capability of IL and the ordered porous channels of the carbon supports. Detailed porosity analysis revealed that the IL with an aromatic cation and an oxygenate anion preferred to fill the micropores, and a thin layer was created on the surface of the mesopores. Strong π-π interaction between the IL layer and the carbon surface was disclosed by wide-angle X-ray scattering (WAXS) analysis, leading to enhanced thermal stability of the IL phase. For the same lL coating amount, the DAC of CO2 evaluation revealed that a larger mesopore size and pore volume in the carbon/IL composite materials led to higher CO2 uptake capacity by exposing more active sites to integrate CO2 from diluted sources. The thermodynamic analysis confirmed the critical role of IL coating in providing strong chemisorption sites and significantly improved selectivity to enrich the diluted CO2 from the air atmosphere. This work provides guidance on leveraging the scaffolds' surface properties and porosities of the scaffolds to optimize DAC of CO2 behavior.

Exploitation of Pore Structure for Increased CO2 Selectivity in Type 3 Porous Liquids.

CO2 capture requires materials with high adsorption selectivity and an industrial ease of implementation. To address these needs, a new class of porous materials was recently developed that combines the fluidity of solvents with the porosity of solids. Type 3 porous liquids (PLs) composed of solvents and metal-organic frameworks (MOFs) offer a promising alternative to current liquid carbon capture methods due to the inherent tunability of the nanoporous MOFs. However, the effects of MOF structural features and solvent properties on CO2-MOF interactions within PLs are not well understood. Herein experimental and computational data of CO2 gas adsorption isotherms were used to elucidate both solvent and pore structure influences on ZIF-based PLs. The roles of the pore structure including solvent size exclusion, structural environment, and MOF porosity on PL CO2 uptake were examined. A comparison of the pore structure and pore aperture was performed using ZIF-8, ZIF-L, and amorphous-ZIF-8. Adsorption experiments here have verified our previously proposed solvent size design principle for ZIF-based PLs (1.8× ZIF pore aperture). Furthermore, the CO2 adsorption isotherms of the ZIF-based PLs indicated that judicious selection of the pore environment allows for an increase in CO2 selectivity greater than expected from the individual PL components or their combination. This nonlinear increase in the CO2 selectivity is an emergent behavior resulting from the complex mixture of components specific to the ZIF-L + 2'-hydroxyacetophenone-based PL.

Amine-impregnated cellulose aerogels prepared from old corrugated containers: Microstructure characterization and CO2 capture performance

Here, five different amines (MEA, DETA, TEPA, PEI, and PEPA) were immobilized onto a mesoporous cellulose aerogels (CAs) support prepared from old corrugated containers (OCCs) using the impregnation method, and the thermal stabilities, pore structures, and CO2 adsorption capacities of the resulting amine loaded materials were investigated. The results showed that the thermal stabilities and pore textures of the materials decreased relative to the unmodified CAs support. Additionally, the addition of high molecular weight amines improved the thermal stability of the resulting materials, in the order of PEI>PEPA>TEPA>DETA>MEA. The adsorption capacities of the five Amine40@CAs materials tested ranged from 111.76 to 62.48 mg.g−1 and were in the order of DETA>PEI>MEA>TEPA>PEPA. Considering both thermal stability and CO2 adsorption capacity, PEI is the most suitable for physical immobilization in the CAs support. Consequently, the sample loaded with 30 % PEI exhibits a maximum CO2 capture capacity of 136.84 mg.g−1 material. However, a loading above 30 % results in pore blockage due to amine infiltration into the pore structure, leading to a decrease in the specific surface area and hence the CO2 adsorption capacity. This indicates that there is a balance to be struck between amine loading and CO2 uptake in the solid amine adsorbents using the physical impregnation method, and it is necessary to choose an appropriate method for improving the pore structure in order to maximize the amine loading and thus enhance the CO2 capture capacity.

Низкоуглеродное развитие севера Западной Сибири: климатические проекты на основе природных решений

Active anthropogenic activity is one of the main causes of serious environmental problems that hinder the development of the Arctic zone of Western Siberia — the most important resource potential of the country. The implementation of climate projects based on natural solutions is one of the areas of envi-ronmentally oriented economic growth. The formation and development of sequestration business is possible if there are conditions ensuring its economic efficiency. The article estimates the costs of absorbing of 1 ton of greenhouse gases during the implementation of climate projects in the northern taiga of Western Siberia. To achieve the goal, the predicted values of carbon sequestered from the atmosphere were calculated for different project scenarios. The CO2 effect was measured and the costs of carbon sequestration by tree and shrub communities of willow, alder and pine were analyzed. Alder monocultures showed the largest volumes of CO2 uptake and the lowest costs per carbon unit according to the carbon discounting model. CO2 duration analysis shows the sensitivity of the cost per carbon unit of a climate project based on alder monocultures to changes in the discount rate. The break-even price of a carbon unit is substantiated, which allows comparing it with the market price and drawing conclusions about the economic efficiency of the climate project on carbon sequestration. The study results provide practical recommendations for making decisions about investing in nature-based climate projects for low-carbon development in northern Western Siberia. The methodological approaches disclosed in the article can be used in other regions of Russia.

Pre-treatment of waste hydrated cement used for replacement of fine aggregate using amine-based CO2 solvent

In the realm of construction and demolition (C&D) waste, a small fraction of hydrated cement waste is typically repurposed to generate supplementary cementitious material or filler for concrete. However, the conventional method of utilizing it in powder form demands significant energy consumption to achieve the necessary fineness. Therefore, this study proposes a method to use a waste-hydrated cement paste as a fine aggregate as well as the pre-treatment method to enhance its properties. The pre-treatment involves carbonating hydrated cement in a fully CO2-dissolved amine-based CO2 solvent, specifically a monoethanolamine (MEA) solution. This process eliminates vulnerable phases, such as calcium hydroxide, resulting in a higher compressive strength of mortar when incorporating the treated hydrated cement as fine aggregate. Notably, the use of fully CO2-dissolved 1% and 10% MEA solutions during carbonation demonstrates superior performance and increased CO2 uptake. Additionally, the developed pre-treatment method uses MEA CO2 solvent directly, commonly utilized for CO2 capture in industrial flue gas. It is an alternative for solvent regeneration without the need for a heating process, potentially reducing overall energy consumption.

Study on the homologous effects on the performance of alkali metal-doping MgO-based adsorbents for CO2 capture

In this article, MgO-based adsorbents with different structure and surface property were prepared by combustion of the colloids containing Mg and alkali metal. At the same time, CO2 adsorption performance tests are conducted to compare the doping effect of alkali metal on MgO adsorbents. As confirmed, the introduction of lithium, sodium, and potassium can reduce the grain size of MgO and enhance the basicity, especially increasing the concentration of oxygen vacancies on MgO surface which exposed more basic adsorption active sites and was more conducive to CO2 adsorption. Among them, the one doped with 0.5 % K which had more electron shell numbers showed larger surface area and smaller crystal size. Most importantly, it provided more number of basic sites along with the improved strength of surface basicity due to the more oxygen vacancies. As a result, the maximum CO2 uptake (1.09 mmol/g) at the adsorption time of 60 min can be obtained which still remained at 0.67 mmol/g after 16 cycles of CO2 adsorption–desorption. With the aid of N2 physical adsorption, inductively coupled plasma-optical emission spectroscopy, powder X-ray diffraction, scanning electron microscope, X-ray photoelectron spectroscopy, electron paramagnetic resonance, and chemical adsorption, the relationship between CO2 adsorption capacity of MgO-based adsorbent and homologous regularity of alkali metal was disclosed. In other words, by comparing the CO2 adsorption performance of MgO adsorbents prepared by doping different alkali metals, CO2 adsorption capacity increased with the increase of electron shell numbers. Such a configuration is in favor of the electron supply of the p-orbitals and weakens the Mg–O bonds which promoted the formation of oxygen vacancies. The found will provide in-depth understanding for the modification and performance improvement of MgO-based adsorbents.

Hierarchically porous MgO/biochar composites for efficient CO2 capture: Structure, performance and mechanism

For enhancing the CO2 uptake performance of MgO-based materials, hierarchically porous MgO/biochar composites were prepared using a microwave-assisted hydrothermal method. The CO2 adsorption properties was investigated in detail and the adsorption mechanism was revealed by considering structure − function relationships and performing density functional theory calculations. The MgO/biochar-1 had hierarchical pore structure and high specific surface area (1453 m2·g−1) with abundant narrow micropores (<1.0 nm), facilitating the adsorption of CO2. The results demonstrated that MgO/biochar-1 exhibited the highest CO2 capture capacity of 6.65 mol⋅kg−1 (273 K, 1 bar) and excellent selectivity for CO2/N2 (96.70 at CO2/N2 = 15:85, v/v). After 3 cycles, the adsorption capacity of MgO/biochar-1 still remained at 5.70 mol⋅kg−1 (273 K, 1 bar), suggesting the well cycling performance. The results of density functional theory calculation indicated that the oxygen-containing functional groups and MgO particles substantially enhanced the CO2 capture performance due to the enhanced interactions between MgO/biochar and CO2. This study provides novel insights for the construction of efficient and cheap solid adsorbents for CO2 capture.

The utility of MOF-based materials in direct air capture (DAC) application to ppm-level CO2

Metal-organic frameworks (MOFs) are well-suited materials for CO2 removal and have robust capture capacity and selectivity. Although the adsorption of CO2 in MOFs has been studied, the implementation of ppm-level CO2 uptake in MOFs and the effects of the pore size and charge have not been fully explored. We performed grand canonical Monte Carlo (GCMC) simulations combined with the Density Functional Theory plus U (DFT + U) charge method to investigate MOF screening for ppm-level CO2 uptake and its application in a direct air capture (DAC) system. Three types of MOFs containing eight members were studied: i.e., ZIF-68, 69, 70; UiO-66, 67, 68; CAU-10; and MIL-125. The pore landscape characterization, electrostatic field-induced enhancement, and preferential binding sites of these MOFs were examined for CO2 capture. MOFs with pore limited diameters (PLD) 1.5 times the size of CO2 molecules and with large cavity diameters (LCD) smaller than 10 Å exhibit robust confinement capacity. Polar functional groups and metal ions dominate the electrostatic contributions and subsequently enhance the surface adhesion of CO2 molecules. For a given framework, favorable CO2 binding occurs in the following order: small pores/cages > polar functional group/metal ions > larger pores/cages. ZIF-69 which comprises smaller pores (7.5 Å) and robust polar functional groups (–Cl) collectively enhances CO2 capture; thus, ZIF-69 outperforms other MOFs; the performance of ZIF-69 is followed by that of CAU-10 which has an optimal pore size of 6 Å. These findings are of fundamental and practical importance for the application of MOFs in DAC technologies for CO2 removal.

Rare earth oxide promoted Ru/Al2O3 dual function materials for CO2 capture and methanation: An operando DRIFTS and TGA study

Dual-function materials (DFMs) combine sorbent and catalytic components to perform selective CO2 capture and subsequent hydrogenation. This study explores the performance of rare-earth oxides (REOs) as CO2 adsorption sites on Ru/Al2O3. REOs increase CO2 uptake by upwards of +60 % by enhancing the overall catalyst surface basicity and favoring metal–support interactions. Thermogravimetric analysis during CO2 adsorption-hydrogenation cycles exhibited significant catalytic activity and enhanced stability of Ru-REO/Al2O3 at temperatures as low as 200 °C. This leads to methane production of 50–85 µmol g−1, surpassing recently reported values obtained for alkali and alkali-earth promoted Ru-based materials operated at 250 °C. The highest performing studied DFM, RuNd2O3/Al2O3, achieved 85 % CO2 capture efficiency and steadily produced methane in cyclic operation (+120 % CO2 uptake relative to Ru/Al2O3). Operando DRIFTS revealed that the dominant mechanism for methane formation is the hydrogenation of ruthenium carbonyls, which are stabilized by REOs. Upon CO2 exposure, surface carbonates and bicarbonate species form more abundantly on DFMs than on Ru/Al2O3. This confirms that REOs enhance the adsorption and retention of carbonates, which generate additional promoter-related reaction pathways during low-temperature hydrogenation. These findings are crucial in the advancement of sustainable, wider operation range carbon capture and utilization technologies.

Monometallic/Bimetallic Co‐ZIFs Synthesis, Characterization, and Application for Adsorption of SO2 and CO2 in Continuous Flow System

ABSTRACTSulfur dioxide is serious ultimatum to human health as well as environment, while carbon dioxide is viewed as one of the primary drivers of the worldwide temperature alteration. Therefore, capturing of these gases is a dynamic research subject attracting much consideration from scientists. Herein, we report synthesis of a series of Co‐ZIF and bimetallic M‐Co‐ZIF adsorbents and application for room temperature adsorption of SO2 and CO2. In this work, the breakthrough curves for the adsorption of sulfur dioxide and carbon dioxide on Co‐ZIF and M‐Co‐ZIF were obtained experimentally and theoretically using a laboratory‐scale fixed bed column at room temperature. In this work, the adsorption capacities and breakthrough points for modified bimetallic M‐Co‐ZIF were found to be relatively higher than parent Co‐ZIF. Notably, a high SO2 uptake capacity of 7.1 mmol/g for Zr‐Co‐ZIF and high CO2 uptake capacity of 69.9 mmol/g for Ni‐Co‐ZIF were achieved. The parent cobalt and bimetallic ZIF materials were characterized by XRD, FTIR, SEM, and nitrogen physisorption. The XRD results confirm the formation of pure phase highly crystalline ZIF materials while BET analysis suggests high surface area of prepared adsorbents. Finally, the results of dynamic adsorption combined with characterization show great potential for preparation of bimetallic ZIF adsorbents for effective SO2 and CO2 adsorption.

Enhancing cement-based materials hydration and carbonation efficiency with pre-carbonated lime mud

Lime mud (LM) is a highly alkaline solid waste generated during the papermaking process, and its direct application in cement-based materials can result in insufficient material properties. Pre-carbonation can reduce the alkalinity of LM and improve its ability as a supplementary cementitious material. This study explored the potential of pre-carbonated lime mud (CLM) to partially replace Portland cement under normal and carbonation curing. It was found that CLM absorbed some CO2 and reduced a small amount of alkalinity after pre-carbonation treatment. Under normal curing conditions, LM can promote the hydration reaction at an early age but inhibit subsequent cement hydration due to its alkalinity. In contrast, CLM significantly alleviated the negative impacts of directly incorporating LM into Portland cement. Under carbonation curing conditions, a significant improvement in the compressive strength of cement-based materials containing LM and CLM was observed. The alkaline properties and nucleation effects of CLM and LM enhanced CO2 sequestration efficiency. Especially after 14 days of carbonation curing, the sample with CLM exhibited higher CO2 uptake and better mechanical properties than the sample with LM. This study provides a new solution to improve the resource utilization of LM and mitigates the negative impacts of LM on cement-based materials.

Feasibility of biochar for low-emission soft clay stabilization using CO2 curing

Use of traditional lime-cement binders on stabilizing soft sensitive clays pose a significant challenge for the construction sector to reach Finland’s carbon neutrality goals by 2030. Traditional stabilization recipes consisting of cement as binders contributing significantly to CO2 emissions (≅ 500 kg CO2 eq./ton in deep mixing alone). This laboratory study explores the feasibility of achieving near carbon-negative stabilization of soft clay leveraging accelerated CO2 curing (ACC) in biochar (BC) enhanced cementitious composites. BC, a by-product of the biofuel industry, is used as partial replacement of cement (0 %, 10 %, and 50 % of binder) in developing precast cementitious piles. One non-carbonated treatment and two ACC treatments are employed to assess their uniaxial compressive strength, thermogravimetric properties and CO2 sequestration capacity. The results demonstrate that synergistic effects of using BC with ACC not only enhances the compressive strength of the composites but also promotes CO2 uptake due to formation of stable carbonates. BC due to its surface functional groups, honeycomb porous structure, and hydrophilicity facilitated uniform CO2 diffusion in the clay matrix and likely improved internal curing. In ACC treated composites, the replacement of 50 % of cement with BC resulted in sufficient load-bearing capacity (≥50 kPa as per Finnish Guidelines) for both shallow and deep clay layers, making a suitable subgrade media for many types of geotechnical applications. The measured bound CO2 increased gravimetrically from 2 % to 41 % when cement was partially replaced by BC. In case of non-carbonated samples, 10 % partial replacement of BC provided high strength (≥200kPa). Life Cycle Assessment (LCA) of a case study of utilizing BC stabilized clay in deep mixing operations can potentially reduce net carbon emissions to −50 kg CO2 eq./ton.

Synergistic effects of CO2 mixing and CO2 curing in CO2 uptake capacity of Portland cement

This study investigates the synergistic effects of CO2 mixing and CO2 curing on the CO2 uptake capacity of Portland cement. After a normal mixing or ten minutes of CO2 mixing, samples underwent 0.5, 1, or 3 days of CO2 curing at a 10 % CO2 concentration. Hydration and carbonation characteristics were assessed by means of a thermogravimetry analysis, reacted water and CO2 uptake measurements, pore solution analysis, X-ray diffractometry, and Rietveld-refinement-based quantification. The CO2-mixed samples displayed an escalating trend in terms of CO2 uptake with longer curing times and greater reaction degrees compared to normally mixed samples. In addition, extended CO2 curing durations resulted in decreased levels of portlandite and increased amounts of crystalline carbonates, alongside a reduction in the ratio of amorphous to crystalline carbonates. Subsequently, improvements in the compressive strength were noted with longer CO2 curing durations.

Reversible Multi-Complexation of CO2 to Alkaline Earth Metal Ion-Pair at 400 ppm and 298 K.

The efficient capture of low-pressure CO2 remains a significant challenge due to the lack of established multi-complexation of CO2 to active sites in microporous materials. In this study, we introduce a novel concept of reversible multi-complexation of CO2 to alkaline earth metal (AEM) ion pairs, utilizing a host site in ferrierite-type zeolite (FER). This unique site constrains two AEM ions in proximity, thereby enhancing and isotopically spreading their electrostatic potentials within the zeolite cavity. This electrostatic potential-engineered micropore can trap up to four CO2 molecules, forming M2+-(CO2)n-M2+ (n = 0-4, M = Ca, Sr, Ba) complexes, where each CO2 molecule is stabilized by interactions between terminal oxygen (Ot) in CO2 and the AEM ions. Notably, the Ba2+ pair site exhibits higher thermodynamic stability for multiple adsorptions due to the optimal binding mode of Ba2+-Ot-Ba2+. Through high-accuracy energy calculations, we established the relationship among structure, CO2 uptake, and operating temperature/pressure, demonstrating that the Ba2+ pair site can reversibly capture four CO2 molecules even at concentrations as low as 400 ppm and at 298 K. The findings in the present study provide a new direction for developing efficient CO2 adsorbents.

Mixture of biochar as a green additive in cement-based materials for carbon dioxide sequestration

Cement production for concrete is one of the main reasons why the building industry contributes significantly to carbon dioxide emissions. This paper investigates an innovative approach to utilizing CO2 by incorporating mixed biochar in mortar. Various dosages (0%, 3%, 5%, and 10%) of mixed biochar were explored to assess their impact on the structural properties and environmental sustainability. In this study, mixed biochar was prepared using the pyrolysis method, in which biomasses (rice husk and sawdust) were heated in the absence of oxygen for 2 h in a muffle furnace at the heating rate of 10 ℃/min to 550 ℃ with a 2-h holding time. The replacement of biochar was done with cement in a mortar mixture for casting the cubes followed by putting them in the carbonation chamber for 28 days curing. After that, the cured samples were tested for mechanical strength, porosity, density, and water absorption. X-ray diffraction (XRD) and thermo-gravimetric analysis (TGA) showed that biochar supplementation promoted cement hydration products. Field emission scanning electron microscope (FESEM) analysis showed that several cement hydrates such as C-S–H, Ca(OH)2, and CaCO3 were formed with different doses of biochar and increased mechanical strength. Addition of 10 wt. % biochar increased the compressive strength of the composite by 24.2% than the control respectively, and successfully promoted the CO2 sequestration with 6% CO2 uptake after 28 days of accelerated CO2 curing. The present research has shown the benefits of optimally integrating mixed biochar with cement in the development of low-carbon, sustainable cementitious materials that have the potential to convert building materials like concrete in the future.

Identification and Analysis of Aluminum-Activated Malate Transporter Gene Family Reveals Functional Diversification in Orchidaceae and the Expression Patterns of Dendrobium catenatum Aluminum-Activated Malate Transporters.

Aluminum-activated malate transporter (ALMT) genes play an important role in aluminum ion (Al3+) tolerance, fruit acidity, and stomatal movement. Although decades of research have been carried out in many plants, there is little knowledge about the roles of ALMT in Orchidaceae. In this study, 34 ALMT genes were identified in the genomes of four orchid species. Specifically, ten ALMT genes were found in Dendrobium chrysotoxum and D. catenatum, and seven were found in Apostasia shenzhenica and Phalaenopsis equestris. These ALMT genes were further categorized into four clades (clades 1-4) based on phylogenetic relationships. Sequence alignment and conserved motif analysis revealed that most orchid ALMT proteins contain conserved regions (TM1, GABA binding motif, and WEP motif). We also discovered a unique motif (19) belonging to clade 1, which can serve as a specifically identified characteristic. Comparison with the gene structure of AtALMT genes (Arabidopsis thaliana) showed that the gene structure of ALMT was conserved across species, but the introns were longer in orchids. The promoters of orchid ALMT genes contain many light-responsive and hormone-responsive elements, suggesting that their expression may be regulated by light and phytohormones. Chromosomal localization and collinear analysis of D. chrysotoxum indicated that tandem duplication (TD) is the main reason for the difference in the number of ALMT genes in these orchids. D. catenatum was chosen for the RT-qPCR experiment, and the results showed that the DcaALMT gene expression pattern varied in different tissues. The expression of DcaALMT1-9 was significantly changed after ABA treatment. Combining the circadian CO2 uptake rate, titratable total acid, and RT-qPCR data analysis, most DcaALMT genes were highly expressed at night and around dawn. The result revealed that DcaALMT genes might be involved in photosynthate accumulation. The above study provides more comprehensive information for the ALMT gene family in Orchidaceae and a basis for subsequent functional analysis.

Ceria-boosted Ni/Al2O3 catalysts for enhanced H2 production via acetic acid dry reforming

Acetic acid dry reforming (ADR) is a promising route for sustainable H2 generation. However, coke inhibition during ADR is the main challenge and not resolved by using suitable promoted catalysts. In this work, Ce promotion on 10%Ni/Al2O3 catalysts with 1-5 wt%Ce was evaluated for ADR at varied temperatures of 923–998 K and stoichiometric feed in a fixed-bed rig. CeO2 addition of 1–3% enhanced metal dispersion, and surface area whilst basic CeO2 character significantly boosted the concentration and density of basic sites on catalysts. Particularly, the CO2 uptake of promoted catalysts was about 2.49–3.73 times greater than that of counterpart sample. CH3COOH and CO2 conversions were enhanced with rising Ce loading and the highest reactant conversions were observed at 3 wt%Ce. The improved adsorption of acidic CH3COOH and CO2 molecules due to increasing amount of basic sites as well as redox attributes of CeO2 promoter could be responsible for the enhancement in ADR activity and yield of H2 and CO. The mechanistic two-step pathway for coke suppression induced by CeO2 promotion was elaborated in this work. Generally, carbonaceous species formation on 3%Ce–10%Ni/Al2O3 was considerably reduced about 1.6–2.0 times. H2/CO ratio varied from 0.59 to 0.65 relying on ADR temperature over 3%Ce–10%Ni/Al2O3. These H2/CO values, two times higher than theoretical H2/CO ratio in ADR, are compatible for downstream gas-to-liquid processes to selectively yield high molecular weight olefins. Water formation rate increased from 8.67 × 10−6 to 4.71 × 10−5molH2O gcat−1 s−1 with rising temperature within 923–998 K on 3%Ce–10%Ni/Al2O3.

Entropy‐Driven Carbon Dioxide Capture: The Role of High Salinity and Hydrophobic Monoethanolamine

Addressing atmospheric CO2 levels during the transition to carbon neutrality requires efficient CO2 capture methods. Aqueous amine scrubbing dominates large‐scale flue gas capture but is hampered by the energy‐intensive regeneration step, sorbent loss, and consequent environmental concerns with volatile amines. Herein, hydrophobic non‐volatile alkylated monoethanolamine (MEA) is introduced as a water‐lean CO2 absorbent in brine. The effects of alkylation of MEA, salinity, and aggregation of absorbents on the improved CO2 capture process are systematically investigated. The CO2 absorption facilitates spontaneous self‐aggregation of hydrophobic absorbents, which increases the entropy of water in high‐ion strength solutions. This effect is controlled by the salinity of aqueous solutions, affording comparative gravimetric CO2 uptake performance to benchmark MEA. It is experimentally verified that the hydrophobicity of alkylated MEAs in saline water is responsible for facile absorption, and also for mild regeneration conditions. Therefore, the entropy‐driven approach minimizes absorbent evaporation, corrosion, and decomposition, thus paving the way to realize energy‐efficient carbon capture.

Synthesis of metal-phenanthroline-modified hypercrosslinked polymer for enhanced CO2 capture and conversion via chemical and photocatalytic methods under ambient conditions

Catalytic conversion of CO2 into valuable chemicals is a promising approach to mitigate the greenhouse effect and alleviate energy shortages. Hypercrosslinked polymers (HCPs) offer a scalable and stable platform for this conversion, but they often suffer from low CO2 adsorption and activation capabilities, necessitating high temperatures and pressures for effectiveness. To overcome these limitations, nitrogen-based CO2-philic active sites have been integrated into the structure of HCPs, enhancing CO2 attraction and leading to superior adsorption performance. The incorporation of cobalt ions further bolsters CO2 affinity, with HCP-PNTL-Co-B achieving the highest observed adsorption heat of 33.0 kJ·mol-1 alongside a substantial 2.0 mmol·g-1 CO2 uptake. These modified HCPs exhibit higher yields and reaction rates in cycloaddition reactions with cocatalyst tetrabutylammonium bromide at room temperature and atmospheric pressure, while HCP-1,10-phenanthroline (PNTL)-Co-B demonstrates a higher CO production rate (2,173 μmol·g-1·h-1) and selectivity (84%) in photocatalytic reduction reaction. This research has successfully achieved outstanding carbon dioxide capture and conversion performance at room temperature and atmospheric pressure by introducing CO2-philic active sites and cobalt ions into HCPs via facile one-step polymerization. This study provides a new method to design highly efficient organic catalysts for CO2 conversion.