CO2 Selectivity Research Articles

Synergistic N-heterocyclic carbene and C2N integration for efficient and selective metal-free photocatalytic CO reduction to C2H5OH

In the pursuit of sustainable and highly efficient catalysts for the reduction of CO to valuable multi-carbon fuels, this study presents a novel metal-free catalyst, C/C2N, created by integrating N-heterocyclic carbene (NHC) into a C2N monolayer. Utilizing density functional theory, we demonstrate that this integration effectively addresses the individual limitations of C2N and NHC, neither of which can stably adsorb CO molecules on their own. The synergistic effect of C2N and NHC facilitates distinct CO adsorption energies on the C2N surface (−0.08 eV) and at the NHC site (−0.83 eV), leading to an exceptionally low C–C coupling energy barrier of 0.41 eV, surpassing traditional metal-based catalysts. Computational results reveal that C/C2N exhibits outstanding activity and selectivity in reducing CO to C2H5OH, with a remarkably low free energy barrier of only 0.34 eV, further reducible to 0.20 eV under alkaline conditions. Furthermore, the integration of NHC into the C2N monolayer markedly narrows its band gap, enhancing visible light absorption and optimizing band edge positions, suggesting its potential for visible-light-driven reactions. Our findings establish C/C2N as an effective and selective metal-free photocatalyst with a notably low C–C coupling energy barrier, offering a novel avenue for CO conversion to multi-carbon fuels.

Impact of metal precursor and molar ratios on adsorption and separation of CO2 and CH4 by SOD-ZIF-67 prepared using green solvent-free synthesis

The subclass of metal-organic frameworks (MOFs) known as SOD-ZIF-67 (Sodalite Co (mIm)2, with mIm = 2-methylimidazole) has demonstrated exceptional performance in carbon dioxide (CO2) adsorption and separation. Traditional synthesis methods for SOD-ZIF-67 are often time-consuming and require significant quantities of organic solvents. This study introduces an enhanced, eco-friendly, solvent-free method for synthesizing SOD-ZIF-67. In this approach, SOD-ZIF-67 is produced within 1 h by mechanically grinding a cobalt (Co) metal precursor with an organic linker (mIm), eliminating the need for solvents. The properties of the synthesized SOD-ZIF-67 samples were confirmed through various characterization techniques. Thermal stability tests indicated that the synthesized SOD-ZIF-67 could endure temperatures up to 673 K. Among the samples prepared with different molar ratios, the SOD-ZIF-67 sample with a Co to HmIm molar ratio of 2:1 (denoted as Z-2) demonstrated the highest BET surface area and pore volume, measuring 1923 m2/g and 0.72 cm3/g, respectively. Z-2 exhibited uniform and narrow ultramicropores measuring 0.54 nm, and demonstrated a CO2 adsorption capacity of 91.52 mg (CO2)/g (2.08 mmol/g) at 298 K and 100 kPa. The material showed high selectivity for CO2 over N2 and CH4, with selectivities of 20.44 for CO2/N2 (0.15:0.85) and 4.28 for CO2/CH4 (0.5:0.5). Additionally, breakthrough experiments with CO2/N2 and CO2/CH4 mixtures validated its dynamic separation efficiency, underscoring Z-2′s suitability for selective CO2 capture from flue gases and natural gas purification.

Competitive sorption of CH₄ and CO₂ on coals: Implications for carbon geo-storage

Geological carbon storage, particularly within coal seams, is recognized as a viable strategy for achieving net-zero emissions. However, following CO₂ injection into the coal seam, limited studies have addressed the competitive sorption dynamics of CH₄ and CO₂ on coal, despite the natural presence of CH₄ in these formations. In this work, sorption experiments were conducted using two types of coal: sub-bituminous coal and anthracite. Initially, pure CH4 and CO2 gases were employed to conduct individual sorption tests. Subsequently, the competitive sorption of CH4 and CO2 was evaluated using pre-mixed binary gas mixtures with varying CH4/CO2 ratios. Further, the displacement effect of CO2 on CH4 was investigated by injecting CO2 into coal samples that had been pre-adsorbed with CH4. The data reveal that, for both coals, the ideal selectivity calculated from pure gas measurements underestimates the corresponding values from real multicomponent systems. Anthracite demonstrates a higher selectivity for CO₂ over CH₄ during both adsorption and desorption processes when compared to the ideal selectivity calculated from pure gas sorption data. Conversely, the sub-bituminous coal initially shows lower selectivity for CO₂ than for CH₄ during adsorption, but this trend reverses and intensifies during desorption. If competitive sorption effects are neglected, coal selectivity for CO₂ over CH₄ under the examined conditions would be underestimated by a factor of 1.5 to 2.5. Due to the competitive sorption effects between CH₄ and CO₂, the Langmuir equilibrium constants for gas mixtures are influenced by compositional changes, leading to dynamic deviations from those observed under pure gas conditions. This finding contrasts with the traditional extended Langmuir model, which presumes that the equilibrium constants remain unchanged regardless of gas composition. In addition, the displacement study underscores the efficacy of CO2 in displacing CH4, with higher CO2 ratios intensifying displacement effects. The study highlights the substantial impact of real multicomponent scenarios on coal selectivity for CO₂ and CH₄, offering deeper insights into predicting competitive sorption behavior between CO₂ and CH₄ during CO₂-enhanced coalbed methane recovery and carbon storage processes.

Rational Designing Microenvironment of Gas-Diffusion Electrodes via Microgel-Augmented CO2 Availability for High-Rate and Selective CO2 Electroreduction to Ethylene.

Efficient electrochemical CO2 reduction reaction (CO2RR) requires advanced gas-diffusion electrodes (GDEs) with tunned microenvironment to overcome low CO2 availability in the vicinity of catalyst layer. Herein, for the first time, pyridine-containing microgels-augmented CO2 availability is presented in Cu2O-based GDE for high-rate CO2 reduction to ethylene, owing to the presence of CO2-phil microgels with amine moieties. Microgels as three-dimensional polymer networks act as CO2 micro-reservoirs to engineer the GDE microenvironment and boost local CO2 availability. The superior ethylene production performance of the GDE modified by 4-vinyl pyridine microgels, as compared with the GDE with diethylaminoethyl methacrylate microgels, indicates the bifunctional effect of pyridine-based microgels to enhance CO2 availability, and electrocatalytic CO2 reduction. While the Faradaic efficiency (FE) of ethylene without microgels was capped at 43% at 300mAcm-2, GDE with the pyridine microgels showed 56% FE of ethylene at 700mAcm-2. A similar trend was observed in zero-gap design, and GDEs showed 58% FE of ethylene at -4.0 cell voltage (>350mAcm-2 current density), resulting in over 2-fold improvement in ethylene production. This study showcases the use of CO2-phil microgels for a higher rate of CO2RR-to-C2+, opening an avenue for several other microgels for more selective and efficient CO2 electrolysis.

Advancements in Methane Dry Reforming: Investigating Nickel–Zeolite Catalysts Enhanced by Promoter Integration

A promising method for converting greenhouse gases such as CO2 and CH4 into useful syngas is the dry reformation of methane (DRM). 5Ni-ZSM-5 and 2 wt.% Ce, Cs, Sr, Fe, and Cu-promoted 5Ni-ZSM-5 catalysts are investigated for the DRM at 700 °C under atmospheric pressure. The characterization, including XRD, TPR, TPD, TPO, N2 adsorption–desorption, TGA, TEM, and Raman spectroscopy, revealed that the catalyst’s active sites are distributed throughout the pore channels and on the surface, contributing to the stability of the catalyst. Specifically, the CO2-TPO followed by the O2-TPO experiment using spent catalysts confirmed the oxidizing capacity of CO2 during the DRM reaction. The Ce-promoted catalyst showed the greatest increase in catalytic activity among other catalysts. The 5Ni+2Ce-ZSM-5 catalyst exhibited twice the concentration of acid sites compared to the Cs-promoted counterpart, even though both catalysts achieved similar quantities of active and basic sites. Without compromising H2 and CO selectivity, this finding underscores the crucial role of acid sites in enhancing CH4 and CO2 conversion. With a GHSV of 42,000 mL/(h.gcat), the 5Ni+2Ce-ZSM-5 catalyst demonstrated impressive CH4 conversion rates of 42% at 700 °C and 70% at 800 °C. The reactants spend more time over catalysts during the subsequent reduction of GHSV to 21,000 mL/(h.gcat), resulting in the best catalytic performance with 80% CH4 and 83% CO2 conversions.

Regulation of surface oxygen vacancy of Cu-CeO2/TiO2 heterostructures via fast Joule heating method for enhanced CO2 electrochemical reduction

Strict control of carbon emissions is crucial for expediting the achievement of carbon neutrality. However, the current CO2RR electrocatalytic exhibits numerous shortcomings that impede the enhancement of catalytic activity. Issues such as lengthy catalyst preparation times, and high levels of precious metal content. Additionally, the aggregation of ultrafine nanoparticles contributes to a rapid deterioration in catalytic performance. Herein, a Joule-heating method is efficiently utilized to synthesize heterostructures nano-catalysts for CO2 electroreduction on carbon cloth substrates. This method takes advantage of the thermoelectric coupling of the carbon cloth to achieve carbothermal reduction, while also regulating phase composition and introduction of oxygen vacancies. The Cu-CeO2/TiO2/CC catalyst synthesized in this method showed a current density in CO2 of −32 mA·cm−2 at −1.0 V (vs. RHE). Notably, this catalyst demonstrated high CO selectivity and Faraday efficiency (FECO) of up to 82.5 % at a low potential of −0.3 V (vs. RHE). Optimal electrochemical performance is achieved at a power of 40 W. The ultra-fast temperature change process prevented the agglomeration of catalyst particles and facilitated the construction of a stable heterogeneous interface with a high oxygen vacancy concentration. In conclusion, this study presents a promising approach, particularly for the rapid preparation of low-cost, highly selective non-precious metal electrocatalysts.

Predicting and understanding photocatalytic CO2 reduction reaction with IR spectroscopy-based interpretable machine learning framework.

The highly selective conversion of carbon dioxide into value-added products is extremely valuable. However, even with the aid of in situ characterization techniques, it remains challenging to directly correlate extensive spectral data carrying microscopic information with macroscopic performance. Herein, we adopted advanced machine learning (ML) approaches to establish an accurate and interpretable relationship between vibrational spectral signals and catalytic performances to uncover hidden physical insights. Focusing on photocatalytic CO2 reduction, our model is shown to effectively and accurately predict the CO production activity and selectivity based solely on the infrared (IR) spectral signals, the generalizability of which is additionally demonstrated with a new Bi5O7I photocatalytic system. More importantly, further model analysis has revealed a novel strategy to steer CO selectivity, the physical sanity of which is verified by a detailed reaction mechanism analysis. This work demonstrates the tremendous potential of machine-learned spectroscopy to efficiently identify reaction control factors, which can further lay the foundation for targeted optimization and reverse design.

Small Conjugated Organic Ligand-Modified Polyoxometalate-Based Hybrid Materials for Boosting Photocatalytic CO2 Reduction.

Photocatalytic carbon dioxide (CO2) reduction to value-added chemicals is a multielectron transfer process, and the crucial step is the synthesis of photocatalysts. The introduction of small conjugated organic ligands can make the catalytic active site of the compound easier to be exposed in the reaction system and fully contact with the substrate, accelerating the photocatalytic reaction process. In this paper, we synthesized two isomorphic compounds, namely, {[Co(mtrz)3·(H2O)2]2·[SiW12O40]}·6H2O (1) and {[Ni(mtrz)3·(H2O)2]2·[SiW12O40]}·6H2O (2) (mtrz = 1-methyl-1,2,4-triazole). We found that compound 1 has a great photocatalytic performance through a series of experiments, with a CO reduction yield of 7364.92 μmol g-1 h-1 and a CO selectivity of 82.5%. Furthermore, the high catalytic activity can be maintained over four cycle experiments. The catalytic mechanism of its photocatalytic system is also elucidated, which provides an idea for realizing efficient catalytic reduction of CO2 to CO.

Enhanced CO₂ Detection Using Potentiometric Sensors Based on PIM‐1/DBU Imidazolate Membranes

AbstractA novel potentiometric sensor for carbon dioxide (CO2) detection utilizing a composite membrane of Polymer of Intrinsic Microporosity (PIM‐1) and 18‐diazabicyclo[5.4.0]undec‐7‐ene imidazolate (DBU‐imidazolate) is presented. The high surface area and gas permeability of PIM‐1, combined with the chemical affinity and ion‐exchange properties of DBU‐imidazolate, contribute to enhanced CO2 sensitivity and selectivity. The research objectives included the synthesis of PIM‐1 and DBU‐imidazolate, the preparation of composite membranes, and the evaluation of their performance as CO2 sensors. Solvent casting and impregnation methods are employed to prepare the membranes, which are characterized using Thermal Gravimetric Analysis (TGA), and Field Emission Scanning Electron Microscopy (FESEM). CO₂ absorption tests and Electrochemical Impedance Spectroscopy (EIS) are conducted to assess the sensors' performance. The PIM‐1/DBU‐imidazolate membrane exhibited high efficiency in CO₂ capture and release. Open circuit voltage (OCV) measurements are performed under varying concentrations of CO2 exposure and cycles of adsorption/desorption. Results show that the membrane achieves steady state faster at higher CO2 concentrations, with a logarithmic relationship between CO2 concentration and voltage variation, indicating potential for CO2 detection in human environments. These results confirm the sensor's ability to detect varying CO2 concentrations, highlighting its potential for reliable and efficient CO2 monitoring in environmental and industrial applications.

Construction of Coordination Spaces with Narrow Pore Windows in Co-Based Metal-Organic Frameworks toward CO2/N2 Separation.

Carbon emission reduction is an important measure to mitigate the greenhouse effect, which has become a hotspot in global climate change research. To contribute to this, here, we fabricated two Co-based metal-organic frameworks (Co-MOFs), namely, {[Co3(NTB)2(bib)]·(DMA)2·(H2O)4}n (DZU-211) and {[Co3(NTB)2(bmip)]·(DMA)2}n (DZU-212) (H3NTB = 4,4',4″-nitrilotribenzoic acid, bib = 1,4-bis(imidazol-1-yl)-butane, bmip = 1,3-bis(2-methyl-1H-imidazol-1-yl)propane) to realize efficient CO2/N2 separation by dividing coordination spaces into suitable pores with narrow windows. DZU-211 reveals a 3D open porous framework, while DZU-212 exhibits a 3D double-fold interpenetrated structure. The two MOFs both possess large coordination spaces and small open pore sizes, via the bib ligand insertion and framework interpenetration, respectively. Comparatively, DZU-211 reveals superior selective CO2 uptake properties due to its more suitable pore characteristics. Gas sorption experiments show that DZU-211 has a CO2 uptake of 52.6 cm3 g-1 with a high simulated CO2/N2 selectivity of 101.7 (298 K, 1 atm) and a moderate initial adsorption heat of 38.1 kJ mol-1. Moreover, dynamic breakthrough experiments confirm the potential application of DZU-211 as a CO2 separation material from postcombustion flue gases.

Synthesis and Characterization of Highly Fluorinated Hydrophobic Rare-Earth Metal-Organic Frameworks (MOFs).

Tuning a material's hydrophobicity is desirable in several industrial applications, such as hydrocarbon storage, separation, selective CO2 capture, oil spill cleanup, and water purification. The introduction of fluorine into rare-earth (RE) metal-organic frameworks (MOFs) can make them hydrophobic. In this work, the linker bis(trifluoromethyl)terephthalic acid (TTA) was used to make highly fluorinated MOFs. The reaction of the TTA and RE3+ (RE: Y, Gd, or Eu) ions resulted in the primitive cubic structure (pcu) exhibiting RE dimer nodes (RE-TTA-pcu). The crystal structure of the RE-TTA-pcu was obtained. The use of the 2-fluorobenzoic acid in the synthesis resulted in fluorinated hexaclusters in the face-centered cubic (fcu) framework (RE-TTA-fcu), analogous to the UiO-66 MOF. The RE-TTA-fcu has fluorine on the linker as well as in the cluster. The MOFs were characterized by powder X-ray diffraction, X-ray photoelectron spectroscopy, thermogravimetric analysis, and contact angle measurements.

Removal performance of Nitrogen, sulfur and chlorine pollutants during chemical looping combustion of textile dyeing sludge using red mud as an oxygen carrier

Textile dyeing sludge (TDS) is a solid waste produced by the textile industry, which contains a large number of N, S and Cl components. Direct heat treatment of TDS will cause a large number of N, S, Cl pollutants to be released. This study verified the possibility of chemical looping combustion (CLC) of TDS using alkaline WS900 red mud (RM) oxygen carrier, which is rich in Na/Ca, to remove N, S and Cl pollutants at the same time. Raising the reaction temperature in the range of 750–900 °C, prolonging the residence time and increasing the oxygen excess coefficient can promote the oxidation performance of WS900 to NOx precursor, while CO2 atmosphere inhibits the oxidation ability. After 10 cycles of CLC, the Cl fixation rate of WS900 is still close to 100% and its S fixation rate is more than 97%. It can maintain more than 90% of carbon conversion and 86% of CO2 selectivity. Compared with the pyrolysis condition, the removal rate of N pollutants is about 67%. Alkaline RM is also neutralized after absorbing acid gases during CLC, which is convenient for its further treatment and utilization.

Confined Intermediates Boost C2+ Selectivity in CO2 Electroreduction

Confined Intermediates Boost C2+ Selectivity in CO₂ Electroreduction

Ni-Mo/Al2O3 catalyst for partial oxidation reforming of low concentration coal bed methane and its application on SOFC

Electricity generation via low concentration coal bed methane (LC-CBM) can save energy and reduce greenhouse gas emissions. Solid oxide fuel cell (SOFC) is a very promising power generation device that can directly utilize various fuels for power generation, but the carbon deposition issue remains the critical challenge when using the traditional nickel-based materials as the anode. In this study, three types of 5Ni/Al2O3, 5Mo/Al2O3, and Ni-Mo/Al2O3 catalysts were prepared and characterized. The Ni-Mo/Al2O3 catalyst show better catalytic activity for CH4 conversion (99.4 %), CO selectivity (98.9 %), H/C ratio (2.15) and stability at 800 °C for 100 h. The single cell with LC-CBM external reforming Ni-Mo/Al2O3 catalyst achieved a peak power density of 0.669 W cm−2 at 800 °C and showed a significant improvement of 160 % compared to that of the direct LC-CBM cell. Additionally, the incorporation of Ni-Mo/Al2O3 catalyst for reforming could also prolong the stability of the cell at 750 °C.

Unraveling the mechanistic interplay between CO and CO2 hydrogenation over Ni, Co, and NiCo catalysts

Although CO and CO2 hydrogenation reactions have been extensively studied, there is still significant controversy regarding the mechanism of methane formation and the routes for byproducts, especially when both carbon sources are simultaneously present. This work combines kinetic, operando-spectroscopic, isotopic techniques and DFT calculations to elucidate the relationships between CO and CO2 hydrogenation over mono Ni, Co and bimetallic NiCo catalysts with similar metal dispersion. The bimetallic catalysts showed a slight synergistic effect for methane formation from CO, while from CO2 the effect was opposite, showing a negative shift of activity as compared with those observed on the monometallic catalysts. The kinetic analysis shows similar apparent order with respect to H2 (∼0.5) and an inverse secondary isotope kinetic effect (<1) for both methanation reactions, suggesting that CH4 formation proceeds via C-O bond breaking in an H*-assisted mechanism, where the rate-determining step was not shown to be sensitive to the carbon source. The anti-synergistic effect observed on the bimetallic catalysts during CO2 hydrogenation is explained by the formation of unreactive HCOO* species (spectator), which generate a lower density of methane intermediates. On the other hand, the formation of the undesired products, i.e., CO or CO2 during CO2 or CO hydrogenation, respectively, shows relevant differences since the CO formation during CO2 hydrogenation proceeds through the desorption of the carbonyl species adsorbed on weak sites, meanwhile the CO2 formation from CO hydrogenation is due to a minority route of direct dissociation of CO, allowing the rejection of O* with CO* to produce CO2. This study contributes to elucidate the routes that determine the selectivity and reactivity for CO and CO2 hydrogenation and their mechanistic relationship. This information is valuable for the rational design and development of new materials with high performance during hydrogenation processes.

Amphiphilic heterojunctions with atomically dispersed copper–alkynyl active units for highly efficient CO2 photoreduction

The efficiency of CO2 photoreduction is limited by slow charge kinetics and the mass transfer of hydrophobic CO2 and H2O over the photocatalyst. Herein, we present a copper–alkynyl bond coordination polymer (CA-CP) with atomically-dispersed copper–alkynyl units (ADCAUs). By incorporating hydrophobic CA-CP with hydrophilic iodine vacancy-rich bismuth oxyhalides (IV-BX), we construct amphiphilic heterojunction photocatalysts (CA-CP/IV-BX) for visible-light-driven CO2 photoreduction. CA-CP/IV-BX achieves excellent stability, 100 % CO selectivity and a CO-evolution rate of 157.6 μmol g−1 h−1 coupled with O2 releasing. Experimental and theoretical calculations elucidate that the ADCAUs favor adsorption and activation of CO2, and have high CO selectivity. Moreover, the amphiphilic janus structure not only ensures the spatial synergy effect of CO2 reduction and H2O oxidation, but also promotes charge separation and proton feeding, boosting CO2 photoreduction activity. This work develops Cu–alkynyl coordination polymer photocatalysts with ADCAUs and provides insights into hydrophobic–hydrophilic biphasic photocatalysts for synergistic CO2 reduction and H2O oxidation.

Manufacturing Single-Atom Alloy Catalysts for Selective CO2 Hydrogenation via Refinement of Isolated-Alloy-Islands.

Single-atom alloy (SAA) catalysts exhibit huge potential in heterogeneous catalysis. Manufacturing SAAs requires complex and expensive synthesis methods to precisely control the atomic scale dispersion to form diluted alloys with less active sites and easy sintering of host metal, which is still in the early stages of development. Here, we address these limitations with a straightforward strategy from a brand-new perspective involving the 'islanding effect' for manufacturing SAAs without dilution: homogeneous RuNi alloys were continuously refined to highly dispersed alloy-islands (~ 1 nm) with completely single-atom sites where the relative metal loading was as high as 40%. Characterized by advanced atomic-resolution techniques, single Ru atoms were bonded with Ni as SAAs with extraordinary long-term stability and no sintering of the host metal. The SAAs exhibited 100% CO selectivity, over 55 times reverse water-gas shift (RWGS) rate than the alloys with Ru cluster sites, and over 3-4 times higher than SAAs by the dilution strategy. This study reports a one-step manufacturing strategy for SAA's using the wetness impregnation method with durable high atomic efficiency and holds promise for large-scale industrial applications.

Enhanced CO2 Reduction on a Cu-Decorated Single-Atom Catalyst via an Inverse Sandwich M-Graphene-Cu Structure.

The highly active and selective electrochemical CO2 reduction reaction (CO2RR) can be exploited to produce valuable chemicals and fuels and is also crucial for achieving clean energy goals and environmental remediation. Decorated single-atom catalysts (D-SACs), which feature synergistic interactions between the active metal site (M) and an axially decorated ligand, have been extensively explored for the CO2RR. Very recently, novel double-atom catalysts (DACs) featuring inverse sandwich structures were theoretically proposed and identified as promising CO2RR electrocatalysts. However, the experimental synthesis of DACs remains a challenge. To facilitate the fabrication and to realize the potential of these novel DACs, we designed a D-SAC system, denoted as M1@gra+Cuslab. This system features a graphene layer with a vacancy-anchored SAC, all stacked on a Cu(111) surface, thereby embodying a Cu slab-supported inverse sandwich M-graphene-Cu structure. Using density functional theory calculations, we evaluated the stability, selectivity, and activity of 27 M1@gra+Cuslab systems (M = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, Hf, Ta, W, Re, Os, Ir, Pt, or Au) and showed five M1@gra+Cuslab (M = Co, Ni, Cu, Rh, or Pd) systems exhibit optimal characteristics for the CO2RR and can potentially outperform their SAC and DAC counterparts. This study offers a new strategy for developing highly efficient CO2RR D-SACs with an inverse sandwich structural moiety.

CoCorrole-Functionalized PCN-222 for Carbon Monoxide Selective Adsorption.

The high risk of CO poisoning justifies the need for indoor air quality control and warning systems based on the detection of low concentrations (ppm-ppb) of CO. Cobalt corrole complexes selectively bind CO vs. O2, CO2, N2, opening new fields of applications. By combining the CO chemisorption properties of cobalt corroles with the known sorption capacity of MOFs, we hope to obtain high performance sensing materials for CO detection. In addition, the exposed metal sites of MOFs lead to CO2 physisorption, allowing the co-detection of CO and CO2. In this work, PCN-222, a stable Zr-based MOF made from Ni(TCPP) with natural vacancies, has been used as a porous matrix for the grafting of electron-poor metallocorroles. The materials were characterized by powder XRD, SEM and optical microscopy, BET analyses and gas adsorption measurements at 298 K. No degradation of the crystalline structure of PCN-222 was observed. At 1 atm, the adsorbed CO(g) volumes measured for the best materials were 12.15 cm3 g-1 and 14.01 cm3 g-1 for CoCorr2@PCN-222 and CoCorr3@PCN-222 respectively, and both materials exhibited high CO chemisorption and selectivity against O2, N2, and CO2 at low pressure due to the highest energy of the chemisorption process vs physisorption.

Activated Carbon for CO2 Adsorption from Avocado Seeds Activated with NaOH: The Significance of the Production Method.

The rise in atmospheric greenhouse gases like CO2 is a primary driver of global warming. Human actions are the primary factor behind the surge in CO2 levels, contributing to two-thirds of the greenhouse effect over the past decade. This study focuses on the chemical activation of avocado seeds with sodium hydroxide (NaOH). The influence of various preparation methods was studied under the same parameters: carbon precursor to NaOH mass ratio, carbonization temperature, and nitrogen flow. For two samples, preliminary thermal treatment was applied (500 °C). NaOH was used in the form of a saturated solution as well as dry NaOH. The same temperature of 850 °C of carbonization combined with chemical activation was applied for all samples. The applied modifications resulted in the following textural parameters: specific surface area from 696 to 1217 m2/g, total pore volume from 0.440 to 0.761 cm3/g, micropore volume from 0.159 to 0.418 cm3/g. The textural parameters were estimated based on nitrogen sorption at -196 °C. The XRD measurements and SEM pictures were also performed. CO2 adsorption was performed at temperatures of 0, 10, 20, and 30 °C and pressure up to 1 bar. In order to calculate the CO2 selectivity over N2 nitrogen adsorption at 20 °C was investigated. The highest CO2 adsorption (4.90 mmol/g) at 1 bar and 0 °C was achieved.