Enhanced CO2 Adsorption Research Articles

Facile synthesis of amine hybrid silica aerogel globule via wet casting assisted self-catalysed sol-gel process for CO2 capture including direct air capture

Amine hybrid silica aerogel globule (AHSAG) for CO2 capture including direct air capture (DAC) was firstly synthesized via wet casting assisted self-catalyzed sol-gel process. AHSAG has abundant interpenetrating macropores, which favors diffusion of CO2 into internal amine sites and can enhance CO2 adsorption kinetics and capacity. The optimal CO2 adsorption capacity of AHSAG with dry 100% and 400 ppm CO2 are 3.82 (30 °C) and 1.86 mmol/g (55 °C), respectively. Corresponding amine efficiencies are 0.478 and 0.233. The effect of temperature on CO2 adsorption capacity is attributed to simultaneous enhancement of mass transfer kinetics and adsorption thermodynamics. The highest CO2 adsorption rate of AHSAG is achieved at 70 and 55 °C with 100% and 400 ppm CO2, respectively. The trend of CO2 adsorption rate with temperature is attributed to the synergistic effect of diffusion kinetics and desorption. Based on experimental CO2 adsorption kinetics, adsorption mechanism in 400 ppm CO2 was estimated with different diffusion models. Both film diffusion resistance and intraparticle diffusion resistance are involved in CO2 capture of AHSAG from air under given condition to control the overall adsorption process. Three kinetics models were used to fit the experimental data of AHSAG for DAC, and the Avrami model showed the best fitting within the whole adsorption period. Comparing with its state-of-the-art counterparts, AHSAG offers significant advantages for practical DAC, such as high adsorption capacity and amine efficiency, fast adsorption kinetics, and excellent cyclic stability.

Enhanced CO adsorption and *CO hydrogenation for efficient CO2 deep reduction on MnCu-NC

In CO2RR, enhancing CO adsorption could suppress desorption and increase *CO concentration for deep reduction. An underlying concern is that strong adsorption might result in high thermodynamic barrier for *CO hydrogenation, however, kinetic barrier firstly dominates the reaction pathway and determines the products selectivity. Directed by above idea, CO2RR performance on Mn, Cu doped nitrogenated carbon (MnCu-NC) is comprehensively studied using density functional theory (DFT). MnCu-NC shows a mild limiting potential of −0.59 V (*CO → *CHO) for CH3OH and CH4 products. CO poisoning is likely to cause catalyst deactivation, while CO modified MnCu-NC shows a slightly increased limiting potential of −0.63 V (*COCO → *COCHO) for CH3OH and CH4, and hydrogen evolution is significantly suppressed. Further comparative studies indicate that kinetic barrier for *CO hydrogenation is crucial for deep reduction, and C–O activation, as well as CO adsorption is enhanced by Π-backbonding. Besides, introduction Cu to dual-atom catalyst (DAC) could help retain more electrons and Mn has strong magnetization for charge transfer, both of which improve the charge densities and Π-backbonding strength, thus boosting the remarkable CO2RR performance toward CH4 and CH3OH on MnCu-NC.

N-doped carbon-supported Cu–CuO nanoparticles for photocatalytic reduction of carbon dioxide

Value-added conversion of CO2 using solar energy is a sustainable strategy to address the energy crisis and environmental issues simultaneously. In this work, Cu–CuO/NC catalysts were successfully prepared by a sol-gel method, and the effects of Cu doping ratio and heat treatment temperature on the catalyst properties were investigated. The experimental results revealed that 7%CNC-600 °C has the best photocatalytic reduction performance of CO2 to CH3OH within 8h, 812μmol/gcat. The catalysts were also analyzed using techniques such as XRD, SEM, TEM, Raman spectroscopy, CO2-TPD, PL, etc. The superior catalytic activity mainly benefits from the electron capture properties of the metal and its synergistic effect with nitrogen-doped carbon, resulting in a significantly improved catalyst optical property, enhanced CO2 adsorption capacity, and improved separation efficiency of photoexcited charges. Furthermore, the combined DRS and VB-XPS results elucidate the photocatalytic reaction mechanism. This study could provide potential strategies for environmental purification and energy conversion.

Sustainable mechanochemical synthesis of catalytically graphitized mesoporous carbons

So far it is difficult to achieve both a high graphitization degree and uniform mesopores in carbons, especially via a sustainable synthesis approach. This work shows that mesoporous graphitized carbons predominantly composed of amorphous and/or partially graphitic carbon nanotubes can be obtained by a simple mechanochemical synthesis using tannins as carbon precursors, iron salt as a graphitization catalyst and block copolymer as a soft template. The one-pot synthesis relied on the fast ball milling of a Pluronic-type template, tannins, and iron salt, followed by the direct thermal treatment at a certain temperature (e.g., 750 °C) leading to mesoporous carbons with a high degree of graphitization (up to 75%), high specific surface areas up to 360 m2/g, and large mesopore volumes up to 0.40 cm3/g. Moreover, the procedure can be extended for the synthesis of highly porous activated carbons with uniform mesoporosity by adding potassium oxalate to the milling system. The procedure afforded activated mesoporous carbons with substantially uniform mesopores of about 7.7 nm, a high specific surface area of 1100 m2/g, a large pore volume of 0.84 cm3/g, and enhanced CO2 adsorption capacity up to 4.0 mmol/g at ambient conditions. This synthetic approach offers advantages in terms of scalability, simplicity, and reduced environmental impact in comparison to traditional synthesis methods.

Amorphous ZnSnOx Hollow Spheres Enable Highly Efficient CO2 Reduction.

Carbon dioxide (CO2) adsorption and electron transport play an important role in CO2 reduction reaction (CO2RR). Herein, we have demonstrated a new class of diverse hollow ZnSnOx (ZSO) through the amorphization of hydroxides to enhance CO2 adsorption and accelerate electron transport. The amorphization is occurred by calcination process, as indicated by Fourier transform infrared spectroscopy and Raman spectra. In particular, the ZnSnOx hollow spheres (ZSO HSs) achieve a high Faradaic efficiency (FE) of HCOOH up to 92.7 % at best, outperforming the commercial ZSO (Comm. ZSO, 85.7 %). ZSO HSs also exhibit durable stability with negligible activity decay after 10 h of successive electrolysis. In-situ attenuated total reflectance infrared absorption spectroscopy further reveals strong adsorption of CO2 and rapid intermediate configuration transformation in amorphous ZSO HSs. This work demonstrates the practical application of ZSO for CO2RR and provides a new insight to create efficient CO2RR electrocatalysts.

Development of an amine-impregnated polymer aerogel for CO2 capture

The synthesis and characterization of amine-impregnated polymer aerogels for CO2 capture represents a groundbreaking advancement in combating the urgent challenges of carbon dioxide (CO2) emissions and climate change mitigation. The traditional way of synthesizing aerogels for CO2 capture is to use a one-step gelation process without functionalizing the aerogel, which, to some extent, has low CO2 capture capacity and kinetics. This study finds a method of synthesizing the functionalized aerogel, which has high CO2 adsorption capacity, faster kinetic, and is more stable. The polymer aerogel was developed using an oil-water emulsion polymerization method, followed by freeze-drying. It was impregnated with a mono-ethanolamine (MEA) solution to enhance CO2 adsorption. The performance of the amine-impregnated poly (AAm-co-AAc) aerogels was tested in a continuous adsorption column filled with aerogel. The adsorption results showed the amine-impregnated aerogels having an amine equilibrium uptake value of 40% had significantly improved CO2 capture capacity up to 2.34 mmole g−1 at 1 bar pressure, 25 °C reaction temperature, and 10 ml/min flow rate. The polymeric aerogel has a very fast adsorption rate, as it can capture 90% of its maximum capacity within just 10 minutes. Then the kinetic data of the CO2 adsorption was modelled and found to best fit on both pseudo-1st and 2nd-order kinetic models, proposing that the adsorption mechanism on aerogel was controlled by surface diffusion and chemisorption. Furthermore, the isotherm data were evaluated and observed to be best represented by the Langmuir isotherm model, suggesting monolayer formation on the aerogel. After five adsorption-desorption cycles, the amine impregnated poly (AAm-co-AAc) aerogel was able to preserve the initial capacity without a significant decrease. These findings underscore the immense ability of amine-impregnated poly (AAm-co-AAc) aerogels as highly efficient adsorbents for CO2 capture, thus offering a speedy adsorption process and showing stable regeneration capacity, thereby exhibiting greater industrial application potential.

Dual hydrogen bond donor functionalized hierarchical porous poly(ionic liquid)s for efficient CO2 fixation into cyclic carbonates

CO2 capture and conversion to high-value-added products is critical for the purposes of environmental preservation and carbon resource utilization. In this study, a novel class of porous poly(ionic liquid)s has been synthesized, incorporating dual hydrogen bond donors (amide and hydroxyl groups) and nucleophiles (Br-) as multiple effective active sites for the cycloaddition reaction between CO2 and epoxides. The presence of dual hydrogen bond donors not only provides two active sites for synergistic catalysis with epoxides but also enhances the capacity for CO2 adsorption. Comprehensive characterization has been conducted to elucidate the structural features and properties of these innovative materials. By regulating the ratio between ionic liquid monomer and divinylbenzene, a hierarchical porous structure favorable for the reaction was constructed, resulting in optimized catalytic activity comparable to that of bulk ionic liquid monomers. Furthermore, this catalyst exhibits remarkable structural stability with minimal activity loss even after five consecutive use cycles. Combining density functional theory calculations with in-situ Fourier transform infrared spectroscopy analysis, the catalytic mechanism was proposed that the dual hydrogen bond donors and Br- synergistically promote ring-opening reactions of epoxides, while amide groups serve as basic sites to enhance CO2 adsorption during the reaction process.

Self-optimized and stable nanocomposites via one-pot synthesis for high-temperature CO2 electrolysis in solid oxide electrolysis cells

Solid oxide electrolysis cells (SOECs) hold the promise of directly converting CO2 into CO fuels with exceptional cost-effectiveness and efficiency. However, the widespread application of SOECs is impeded by the significant lack of highly active and stable cathodes. Herein, a one-pot synthesis strategy is proposed to introduce Cu into a composite consisted of Sr2Fe1.5Mo0.5O6−δ (SFM) and Gd0.2Ce0.8O1.9 (GDC). This strategy leads to the automatic formation of hetero-structured composites, comprising double perovskite, Ruddlesden-Popper perovskite, fluorite, as well as in-situ exsolved Cu–Fe bimetals at high temperatures and operational conditions. Consequently, this approach greatly enhances CO2 adsorption capability, CO2 catalytic activity, O2−/e− conductivity, and ensures good phase compatibility with electrolyte. As results, the La0.8Sr0.2Ga0.8Mg0.2O3−δ electrolyte-supported single cell with the composite cathode achieves a high current density of 2.22 A cm−2 at 850 °C and 1.6 V, which is substantial increase of 65.7% compared to the current density achieved with traditional physically hybrid SFM-GDC cathodes. These results underscore the potential of one-pot synthesized nanocomposites as promising cathodes for CO2 electrolysis in SOECs.

Enhancing CO2 adsorption capacity of hydroxypyridine-based ionic liquids using fluorinated graphene as carrier Material: A density functional theory study

Graphene carriers can improve the properties of ionic liquids and enhance their CO2 capture performance. Density functional theory calculations were employed to evaluate the feasibility of utilizing graphene as a carrier material to enhance the CO2 adsorption capacity of hydroxypyridine-based ionic liquids (ILs). The results indicated that BN co-doped fluorinated graphene represented a promising carrier material capable of weakening the interaction between cations and anions while enhancing the charges of O and N in the anionic species of ILs, thereby increasing the adsorption capacity of ionic liquids for CO2. Furthermore, the microstructure and properties of the graphene-ILs composites were explored. Doping atoms in graphene were found to induce alterations in the distribution of surface electrostatic potential, influencing the adsorption sites of ionic liquids and their properties. Compared to hydrogen-terminated graphene, fluorinated graphene was a more stable carrier material due to its higher binding energy with hydroxypyridine-based ILs. The higher binding energy was not derived from the direct interaction between doped atoms and ILs, but rather from the impact of doped atoms on the electronic structure of graphene. In methanol solvent, the adsorption of ILs on various graphene surfaces was a spontaneous exothermic process, indicating the feasibility of material preparation.

Constructing Highly Efficient ZnO Nanocatalysts with Exposed Extraordinary (110) Facet for CO2 Electroreduction.

Electrochemical reduction of CO2 to highly valuable products is a promising way to reduce CO2 emissions. The shape and facets of metal nanocatalysts are the key parameters in determining the catalytic performance. However, the exposed crystal facets of ZnO with different morphologies and which facets achieve a high performance for CO2 reduction are still controversial. Here, we systematically investigate the effect of the facet-dependent reactivity of reduction of CO2 to CO on ZnO (nanowire, nanosheet, and flower-like). The ZnO nanosheet with exposed (110) facet exhibited prominent catalytic performance with a Faradaic efficiency of CO up to 84% and a current density of -10 mA cm-2 at -1.2 V versus RHE, far outperforming the ZnO nanowire (101) and ZnO nanoflower (103). Based on detailed characterizations and kinetic analysis, the ZnO nanosheet (110) with porous architecture increased the exposure of active sites. Further studies revealed that the high CO selectivity originated from the enhancement of CO2 adsorption and activation on the ZnO (110) facet, which promoted the conversion of CO2 toward CO. This study provides a new way to tailor the activity and selectivity of metal catalysts by engineering exposed specific facets.

Synthesis of hydrophobic CuCl/LaA modified by butyltrichlorosilane towards enhanced CO adsorption under humid environment

Cuprous ion modified molecular sieves have been considered as promising CO adsorbents in gas separation or purification industry. However, it persists as a significant challenge to overcome the unfavorable effect of water vapor in the work environment on gas adsorption and separation. Herein, we propose a synthetic strategy using rare earth element La as an additive to form LaOLa coordination bonds followed by surface silanization treatment to construct a hydrophobic SiOSi barrier to significantly improve the stability of Cu+ under humid atmosphere. By successively introducing La3+ and Cu+ into zeolite 5A, CuCl/LaA adsorbents were prepared via ion exchange and solid dispersion methods. And then by silanization modification using toluene as solvent and butyltrichlorosilane (BTS) as hydrophobic agent, hydrophobic CuCl/LaA-BTS adsorbents were prepared. Dynamic adsorption investigation demonstrated that the as-prepared CuCl/LaA-BTS adsorbents possessed hydrophobic surface and consequently the adsorption capacity of CO was enhanced significantly under humid atmosphere. The CO adsorption breakthrough capacity over CuCl/LaA-BTS attained 0.34 mg/g, which was 5.7 times higher than that of zeolite 5A at 40 °C, atmospheric pressure and a relative humidity of RH = 55 %. Moreover, the CO adsorption capacity of CuCl/LaA-BTS retained 0.31 mg/g after four cycle regenerations. This work provides an effective and novel route for synthesizing highly stable cuprous ion modified zeolite adsorbents.

ZSM-5@MOF-199 core-shell composite adsorbent: Rapid ambient synthesis and CO/CO2 adsorption

Using a hydroxy double salt intermediate, we demonstrated rapid room temperature fabrication of ZSM-5@MOF-199 core–shell sorbents. Copper chloride was compatible with the ZnO-assisted MOF growth scheme. The structural and chemical properties of the composite were fine-tuned through either the core or the shell modification, targeting a superior adsorption capacity for CO and CO2 compared to parent adsorbents. For example, the Na2S2O3-assisted MOF-199 shell reduction enriched surface Cu+ and enhanced CO adsorption capacity. Modulating the zeolite core to protonic hierarchical ZSM-5 (HZSM-5) increased CO and CO2 uptake by 20 % and 28 %, respectively. The isosteric heat of adsorption revealed that the HZSM-5 core altered surface electronic properties and influenced the CO2 adsorption performance. Thermodynamic analysis indicated that the adsorption processes involved a combination of physisorption and electrostatic interactions with an ordered arrangement of adsorbates. The core–shell sorbent can be easily tuned for selective separation of CO and CO2.

Comprehensive investigation of isotherm, RSM, and ANN modeling of CO2 capture by multi-walled carbon nanotube

Chemical vapor deposition was used to produce multi-walled carbon nanotubes (MWCNTs), which were modified by Fe–Ni/AC catalysts to enhance CO2 adsorption. In this study, a new realm of possibilities and potential advancements in CO2 capture technology is unveiled through the unique combination of cutting-edge modeling techniques and utilization of the recently synthesized Fe–Ni/AC catalyst adsorbent. SEM, BET, and FTIR were used to analyze their structure and morphology. The surface area of MWCNT was found to be 240 m2/g, but after modification, it was reduced to 11 m2/g. The modified MWCNT showed increased adsorption capacity with higher pressure and lower temperature, due to the introduction of new adsorption sites and favorable interactions at lower temperatures. At 25 °C and 10 bar, it reached a maximum adsorption capacity of 424.08 mg/g. The optimal values of the pressure, time, and temperature parameters were achieved at 7 bar, 2646 S and 313 K. The Freundlich and Hill models had the highest correlation with the experimental data. The Second-Order and Fractional Order kinetic models fit the adsorption results well. The adsorption process was found to be exothermic and spontaneous. The modified MWCNT has the potential for efficient gas adsorption in fields like gas storage or separation. The regenerated M-MWCNT adsorbent demonstrated the ability to be reused multiple times for the CO2 adsorption process, as evidenced by the study. In this study, a feed-forward MLP artificial neural network model was created using a back-propagation training approach to predict CO2 adsorption. The most suitable and efficient MLP network structure, selected for optimization, consisted of two hidden layers with 25 and 10 neurons, respectively. This network was trained using the Levenberg–Marquardt backpropagation algorithm. An MLP artificial neural network model was created, with a minimum MSE performance of 0.0004247 and an R2 value of 0.99904, indicating its accuracy. The experiment also utilized the blank spreadsheet design within the framework of response surface methodology to predict CO2 adsorption. The proximity between the Predicted R2 value of 0.8899 and the Adjusted R2 value of 0.9016, with a difference of less than 0.2, indicates a high level of similarity. This suggests that the model is exceptionally reliable in its ability to predict future observations, highlighting its robustness.

Composite Molecular Sieve ZSM-5/MCM-48-Based Impregnation Modification for Efficient Adsorption of CO2

Micro/mesoporous materials are low-cost functional materials with the potential for CO2 adsorption. Modifying micro/mesoporous materials is significant for enhancing CO2 adsorption and their high-value utilization. Herein, the micro/mesoporous material of composite molecular sieve ZSM-5/MCM-48 (ZM) was synthesized by a two-step crystallization method using cetyltrimethylammonium bromide as a template, tetraethyl orthosilicate as a silicon source and ZSM-5 seed as part of silicon aluminum source. Tetraethylenepentamine (TEPA) and polyethyleneimine (PEI) were used as impregnation modifiers to modify ZM with amine groups. The results showed that with the increase of amine loadings, both ZM-T60 (Impregnated with TEPA) and ZM-P60 (Impregnated with PEI) functionalized adsorbents exhibited the best adsorption capacities of [Formula: see text] and [Formula: see text] at 60, respectively, when the loading of ZM sample was 60%. The adsorption kinetic analysis showed that the adsorption of CO2 by ZM-T60 and ZM-P60 was a chemisorption-dominated process accompanied by physical adsorption. After 10 adsorption/desorption cycles, the CO2 adsorption capacity of ZM-T60 and ZM-P60 decreased by 8.7% and 2.6%, respectively. This work demonstrates that impregnation modification of the composite molecular sieve to achieve efficient CO2 adsorption has practical application significance.

Carbon Dioxide Adsorption on Iron (III) Oxide Pillarized Na-Montmorillonite

Iron (III) oxide (Fe2O3) pillarized Na-montmorillonite (NaMMT) was prepared by ion-exchanging and calcining three different concentrations (0.025, 0.05, and 0.075 M) of Fe(OH)3 with NaMMT. The obtained materials were then examined for its ability to capture carbon dioxide, using thermogravimetric methods. The structural, compositional, and textural changes caused by pillarization were also examined using XRD, XRF, FTIR, and BET-BJH. The results showed that NaMMT-0.025 (pillared using 0.025 M of Fe(OH)3) and NaMMT-0.075 exhibit superior adsorption capacity compared to NaMMT, with NaMMT-0.025 having the greatest capacity. By contrast, NaMMT-0.05 registers a decrease in the amount of CO2 adsorbed, compared to NaMMT. Using XRF, it was shown that the amount of Fe2O3 present in the samples correspond to the concentration of Fe(OH)3 used in ion-exchange. XRD results shows that the interlayer space of NaMMT barely changed after addition of Fe2O3. Using FTIR, successful pillarization of Fe2O3 is confirmed, and by combining it with BET-BJH, it shows that addition of Fe2O3 could enhance carbon capture by creating favourable pore structures. Overall, it shows that adding an appropriate amount of Fe2O3 to montmorillonite will enhance CO2 adsorption.

Two-dimensional interfacial enhanced CO2 adsorption performance of porous organic amine solids: Structure-activity relationships and DFT calculations

The utilization of inexpensive and efficient amine-functionalized adsorbents has become a research hotspot in post-combustion capture technology. Meanwhile, the structure of the support and the selection of organic amines are the primary considerations affecting the CO2 adsorption performance. Herein, the novel solid amine adsorbent materials with amine-support interfacial effect were successfully synthesized in this study by loading four organic amines (TETA, TEPA, PEHA, and PEI) onto expanded vermiculite (EVMT) support with the layered structure. The results indicated that EVMT-50TETA exhibited superior CO2 adsorption capacity (132.5 mg/g) along with effective regeneration capability. This was attributed to the unique layered structure of EVMT that facilitates the dispersion of TETA on its surface or between layers as well as the formation of hydrogen bonds between surface functional groups (–OH) and amines to enhance the amine-support interfacial interaction. Furthermore, the minimal volume expansion of TETA during CO2 adsorption enables improved diffusion of CO2 in channels and enhanced accessibility to active sites. DFT calculations show higher binding energies and faster CO2 adsorption-diffusion rates between TETA and EVMT support. In situ DRIFTS experiments revealed that the process of CO2 adsorption followed the zwitterion mechanism, in which the zwitterion can be reversibly deprotonated to form ammonium carbamate and carbamic acid. This study provides comprehensive insights into the supports and amines interfacial effects through systematic investigation, offering both simplified synthesis strategies and profound theoretical support for studying solid amine adsorbents.

Synergistic enhancement of CO2 hydrogenation to C5+ hydrocarbons using mixed Fe5C2 and Na-Fe3O4 catalysts: Effects of oxide/carbide ratio, proximity, and reduction

CO2 hydrogenation into sustainable chemical feedstocks and fuels is a pivotal focus of energy research. Fe-based catalysts have emerged as promising candidates due to their high efficiency in the CO2 hydrogenation toward C2–C4 olefins and C5+ hydrocarbons. Fe5C2 is known as the active phase of the CO2 hydrogenation. Therefore, it is imperative to discern the roles of active phases in product distribution. Accordingly, in the present study, Fe5C2 is synthesized separately and physically mixed with Na-Fe3O4. The effects of oxide/carbide ratio, the proximity of active phases, and reduction treatment are investigated. The results show that adding carbide to oxide in an appropriate ratio significantly increases CO2 conversion due to the controlled reduction of the oxide phase and enhanced CO2 adsorption. Additionally, a closer distance (mixed-powder pellets) between Na-Fe3O4 and Fe5C2 results in higher selectivity for C2-C4 olefins and C5+ hydrocarbons and less CH4. Furthermore, the graphitized layers of reduced catalyst (R-Na-Fe3O4/Fe5C2 (70/30 wt%)) enhance the selectivity to C2-C4 olefins (40 %) and C5+ hydrocarbons (35 %) at around 40 % CO2 conversion. In contrast, amorphous carbon in the non-reduced catalyst (NR-Na-Fe3O4/Fe5C2 (70/30 wt%)) favors more C2-C4 paraffins and CH4. Therefore, the interplay between the influential factors, i.e., oxide/carbide ratio, spatial distance, and reduction treatment, can result in tailoring an efficient CO2 hydrogenation catalyst toward the formation of valuable hydrocarbons.

CO2 selective adsorption over O2 on N−doped activated carbon: Experiment and quantum chemistry study

Utilizing flue gas as feedstock for CO2 electro−reduction systems is a promising technology to address problems caused by excessive CO2 emissions. However, the O2 contained in the flue gas has a significant adverse effect on the CO2 reduction. Herein, a facile strategy was proposed to suppress the influence of O2 by constructing a CO2−enriched region. N−doping was demonstrated to be an efficient way to enhance CO2 adsorption selectivity over O2 on activated carbon. The N−doped activated carbon achieved 3.7 times increase in CO2 adsorption selectivity over O2 than that before modification under simulated flue gas atmosphere (75 %N2 + 15 %CO2 + 10 %O2). The distinction in adsorption mechanism between CO2 and O2 was revealed by quantum chemistry study. The increased polarity of the carbon materials favored CO2 adsorption and had less impact on O2 adsorption. The electrostatic interaction between CO2 and carbon material was demonstrated to be enhanced after the introduction of pyridinic N and pyrrolic N, which led to an improvement in the CO2 adsorption capacity. The dispersion interaction, which fully regulated O2 adsorption, was weakened due to the deviation of the O2 adsorption position. This study provided a reference for the subsequent development of CO2 selective adsorption materials.

Catalytic CO Oxidation on the Cu+-Ov-Ce3+ Interface Constructed by an Electrospinning Method for Enhanced CO Adsorption at Low Temperature.

It is crucial to eliminate CO emissions using non-noble catalysts. Cu-based catalysts have been widely applied in CO oxidation, but their activity and stability at low temperatures are still challenging. This study reports the preparation and application of an efficient copper-doped ceria electrospun fiber catalyst prepared by a facile electrospinning method. The obtained 10Cu-Ce fiber catalyst achieved complete CO oxidation at a temperature as low as 90 °C. However, a reference 10Cu/Ce catalyst prepared by the impregnation method needed 110 °C to achieve complete CO oxidation under identical reaction conditions. Asymmetric oxygen vacancies (ASOV) at the interface between copper and cerium were constructed, to effectively absorb gas molecules involved in the reaction, leading to the enhanced oxidation of CO. The exceptional ability of the 10Cu-Ce catalyst to adsorb CO is attributed to its unique structure and surface interaction phase Cu+-Ov-Ce3+, as demonstrated by a series of characterizations and DFT calculations. This novel approach of using electrospinning offers a promising technique for developing low-temperature and non-noble metal-based catalysts.

Unraveling the molecular mechanism for enhanced gas adsorption in mixed-metal MOFs via solid-state NMR spectroscopy

The incorporation of multiple metal ions in metal-organic frameworks (MOFs) through one-pot synthesis can induce unique properties originating from specific atomic-scale spatial apportionment, but the extraction of this crucial information poses challenges. Herein, nondestructive solid-state NMR spectroscopy was used to discern the atomic-scale metal apportionment in a series of bulk Mg1-xCox-MOF-74 samples via identification and quantification of eight distinct arrangements of Mg/Co ions labeled with a 13C-carboxylate, relative to Co content. Due to the structural characteristics of metal-oxygen chains, the number of metal permutations is infinite for Mg1-xCox-MOF-74, making the resolution of atomic-scale metal apportionment particularly challenging. The results were then employed in density functional theory calculations to unravel the molecular mechanism underlying the macroscopic adsorption properties of several industrially significant gases. It is found that the incorporation of weak adsorption sites (Mg2+ for CO and Co2+ for CO2 adsorption) into the MOF structure counterintuitively boosts the gas adsorption energy on strong sites (Co2+ for CO and Mg2+ for CO2 adsorption). Such effect is significant even for Co2+ remote from Mg2+ in the metal-oxygen chain, resulting in a greater enhancement of CO adsorption across a broad composition range, while the enhancement of CO2 adsorption is restricted to Mg2+ with adjacent Co2+. Dynamic breakthrough measurements unambiguously verified the trend in gas adsorption as a function of metal composition. This research thus illuminates the interplay between atomic-scale structures and macroscopic gas adsorption properties in mixed-metal MOFs and derived materials, paving the way for developing superior functional materials.