Study Of CO Adsorption Research Articles

In situ QXAFS study of CO and H2 adsorption on Pt in [PtAu8(PPh3)8]-H[PMo12O40] solid.

The adsorption behaviors of H2 and CO molecules in crown-motif [PtAu8(PPh3)8]-H[PMo12O40] (PtAu8-PMo12) solids were investigated by in situ quick-scan X-ray absorption fine structure (QXAFS) measurements with a time resolution of 0.1 s. The electronic state of Pt in PtAu8-PMo12 was drastically changed by the adsorption of H2 and CO molecules because of the formation of Pt-H2/Pt-CO interactions. H2 was adsorbed more rapidly (<0.5 s) on Pt than CO (∼2.5 s) and showed reversible adsorption/desorption behavior on Pt atoms in PtAu8-PMo12. The rapid adsorption of H2 is due to the fast diffusion of H2, which has a smaller kinetic diameter than CO, in the narrow channels between the closed voids in PtAu8-PMo12. Meanwhile, CO was irreversibly adsorbed on Pt, resulting in structural isomerization to the stable "chalice-motif" PtAu8, which was determined by XAFS analysis and density functional theory calculations. Structural isomerization was involved by pushing ligands aside to make space for CO adsorption as the void size near Pt in the crown-motif PtAu8-PMo12 was narrower than the kinetic diameter of CO.

Experimental and molecular simulation study of CO2 adsorption in ZIF-8: Atomic heat contributions and mechanism

We successfully synthesised ZIF-8 using the solvothermal method at room temperature to study CO2 adsorption storage at 273 and 298 K up to 35 bar. Characterisation methods such as BET, SEM-EDS, XRD, and TGA were used to measure the physical and composition properties of ZIF-8. Grand canonical Monte Carlo (GCMC) simulation was conducted to compare with experimental data and get inside of the CO2 adsorption mechanism by calculating the isosteric heat and its fluid–fluid and solid–fluid contributions. The second was also split into fluid–solid atom contributions to understand in detail the interaction between CO2 and ZIF-8. The analyses revealed that there are three main stages during the CO2 adsorption gas–solid atom contributions, developing, pore-filling and densification. During the developing and pore-filling stages the largest fluid–solid atom contribution to the isosteric heat is CO2-C2 interactions, indicating that the CO2 is adsorbed close to the hexagonal windows of the ZIF-8 structure, while during the densification stage the largest contribution is CO2-N interactions. Where C2 and N refers to C-atom and N-atom, respectively in NCH group of the solid framework. This is because CO2 changes its orientation to be able to accommodate more molecules in the pore cavity. This work provides a better understanding of the adsorption mechanism of CO2 on ZIF-8 and shows how molecular simulation can be used to improve the understanding gas adsorption storage on metal–organic frameworks.

Comparative study of CO adsorption on Au, Cu, MoO2 and MoS2 2D Nanoparticles

This study focuses on a comparative analysis of the electronic properties of triangular, irregular hexagonal, and octagonal 2D nanoparticles containing 10, 12, and 14 motifs, made of Au, Cu, MoO2, and MoS2. The investigation was carried out using density functional theory. The formation energies and vibrational frequencies demonstrate that the 2D nanostructure configurations can exist as stable structures. Edge atoms with lower coordination numbers than central atoms, are the preferred sites for CO adsorption. Using orbital-weighting dual descriptors calculated from Fukui functions enabled the identification of a majority nucleophilic attack sites in Au and Cu nanoparticles, while MoO2 and MoS2-based nanoparticles present almost as many electrophilic sites as nucleophilic sites. The charge transferred between the nanostructures and the CO molecule and the redistribution of the projected density of states were used to assess the strength of interfacial bonds and the nature of the fundamental interaction involved in the bonding.

Hierarchically Porous Structured Adsorbents with Ultrahigh Metal-Organic Framework Loading for CO2 Capture.

Metal-organic frameworks (MOFs) have emerged as promising candidates for CO2 adsorption due to their ultrahigh-specific surface area and highly tunable pore-surface properties. However, their large-scale application is hindered by processing issues associated with their microcrystalline powder nature, such as dustiness, pressure drop, and poor mass transfer within packed beds. To address these challenges, shaping/structuring micron-sized polycrystalline MOF powders into millimeter-sized structured forms while preserving porosity and functionality represents an effective yet challenging approach. In this study, a facile and versatile strategy was employed to integrate moisture-stable and scalable microcrystalline MOFs (UiO-66 and ZIF-8) into a poly(acrylonitrile) matrix to fabricate readily processable, millimeter-sized hierarchically porous structured adsorbents with ultrahigh MOF loadings (∼90 wt %) for direct industrial carbon capture applications. These structured composite beads retained the physicochemical properties and separation performance of the pristine MOF crystal particles. Structured UiO-66 and ZIF-8 exhibited high specific surface areas of 1130 m2 g-1 and 1431 m2 g-1, respectively. The structured UiO-66 achieved a CO2 adsorption capacity of 2.0 mmol g-1 at 1 bar and a dynamic CO2/N2 selectivity of 17 for a CO2/N2 gas mixture with a 15/85 volume ratio at 25 °C. Furthermore, the structured adsorbents exhibited excellent cyclability in static and dynamic CO2 adsorption studies, making them promising candidates for practical application.

Harmonizing Between Chemical Functionality and Surface Area of Porous Organic Polymeric Nanotraps for Tuning Carbon Dioxide Capture.

The energy sector has demonstrated significant enthusiasm for investigating post-combustion CO2 capture, storage, and separation. However, the practical application of current porous adsorbents is impeded by challenges related to cost competitiveness, stability, and scalability. Intregation of heteroatoms in the porous organic polymers (POPs) dispense it more susceptible for CO2 adsorption to attenuate green house gases. In this regard, two hydroxy rich hypercrosslinked POPs, namely Ph/Tt-POP have been developed by one-pot condensation polymerization using a facile synthetic strategy. The high surface areas of both the Ph/Tt-POP (1057 and 893 m2g-1, respectively), and the heteroatom functionality in the POP framework instigated us to explore our material for CO2 adsorption study. The CO2 uptake capacities in Ph/Tt-POP are found to be 2.45 and 2.2 mmol g-1, at 273 K respectively. Further, in-situ static 13C NMR experiment shows that CO2 molecules in Tt-POP appear to be less mobile than those in Ph-POP which probably due to the presence of triazine functional groups along with high abundant -OH groups in the Tt-POP framework. An in-depth study of the CO2 adsorption mechanism by density functional theory (DFT) calculations also shows that CO2 adsorption at the cages formed by two benzyl rings represents the most stable interaction and CO2 molecule is more favorably adsorbed on the Ph-POP with the more negative interaction energies values compared to that of Tt-POP. Further, Non-covalent interaction (NCI) plot reveals that CO2 molecules adsorb more on the Ph-POP than Tt-POP, which can be explain by hydrogen bond formation in case of Tt-POP repeating units turning aside CO2 molecule to interact with the Ph component. Overall, our present study reflects the comprising effects of surface area of the solid adsorbents as well as their functionality can be beneficial for developing efficient hypercrosslinked porous polymers as solid CO2 adsorbent.

Characterisation of Basic Sites on Ga2O3, MgO, and ZnO with Preadsorbed Ethanol and Ammonia-IR Study.

The effect of adsorption of ethanol and ammonia on the basicity of Ga2O3, MgO, and ZnO was examined via IR studies of CO2 adsorption. Ethanol reacts with OH groups on Ga2O3, and MgO, forming ethoxyl groups. The substitution of surface hydroxyls by ethoxyls increases the basicity of the neighbouring oxygen. The ethoxyl groups that also form on ZnO do not contain surface OH groups, but the mechanism of their formation is different. On ZnO, ethoxy groups are formed by the reaction of ethanol with surface oxygens. The presence of ethoxyls on ZnO decreases the basicity because some surface oxygens are already engaged in the bonding of ethoxyl groups. The effect of ammonia adsorption on basicity is different for each oxide. For Ga2O3, ammonia adsorption increases the basicity of neighbouring oxygen sites. Ammonia is not adsorbed on MgO; therefore, it does not change the basicity of this oxide. Ammonia adsorbed on ZnO forms coordination bonds with Zn sites; it does not change the number of basic sites but changes how carbonate species are bonded to surface sites.

&lt;span&gt;Calculations on the stable structures of ScGe&lt;sub&gt;5&lt;/sub&gt; cluster on the potential energy surface and its CO adsorption&lt;/span&gt;

The structures of the ScGe5 cluster were investigated by a combination of the genetic algorithm (GA) with the density functional theory (DFT) calculations. The structural parameters and relative energy of isomers were reported. These doped germanium clusters were applied to study CO adsorption by calculations with PBE functional. The adsorbed structure, the adsorption energy, and the ELF graphs of CO adsorption were also presented. Results indicated that CO molecule can be adsorbed at many positions of these clusters. The positions around the Sc atom can adsorb CO molecule better than others. The Sc-CO model of adsorption is more advantageous than the Sc-OC model. Scandium doped germanium cluster can be used to produce materials that can treat CO gas by adsorption method.

Mesoporous silica supported ionic liquid materials with high efficacy for CO2 adsorption studies

CO2 capture from industrial processes and power plants, contribute to curbing global warming and advancing sustainability efforts. This study involves the design and synthesis of novel mesoporous silica supported ionic liquid based adsorbents for carbon dioxide capture. Utilization of MSILs delves into the efficiency and mechanisms of CO2 adsorption, offering insights for sustainable carbon capture technologies in combating greenhouse gas emissions. 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium ethyl sulfate and 1-ethyl-3-methylimidazolium methylsulfate ionic liquids were anchored on the surface of mesoporous silica which then led to highly efficient adsorbent material. Simple, efficient and cost saving methodology was performed to synthesize such highly efficient CO2 adsorbent materials. In addition, we theoretically predicted the favorable interaction mechanism of chosen molecular entities for CO2 adsorption using density functional theory (DFT) analysis. Theoretical results depict the strong interaction of molecular entities with CO2 gas molecules which is clearly evident from the experimental findings.

MXene/polyaniline/sodium alginate composite gel: Adsorption and regeneration studies and application in Cu(II) and Hg(II) removal

The imperative to efficiently remove heavy metals from water has heightened the demand for adsorbents capable of co-adsorbing heavy metals and offering robust reusability. A novel composite adsorbent (PANI@SA-SNM) was synthesized with amine/sulfur-modified MXene, in-situ polymerized polyaniline (PANI) and sodium alginate (SA). Cu(II) and Hg(II) were used as model pollutants to test the adsorption capacity and stability of the adsorbent. Results showed that this adsorbent illustrated remarkable stability and adaptability across a pH range of 3 to 7 due to the proton transfer effect in PANI. The pseudo-second-order kinetic and Langmuir model were suitable for describing the physical and chemical adsorption process of Cu(II) and Hg(II). Thermodynamic analysis confirmed the adsorption process to be spontaneous and endothermic. The maximum adsorption capacity calculated by the Langmuir model was 255.81 mg g−1 for Cu(II) and 352.76 mg g−1 for Hg(II) (C0 = 50 ∼ 1000 mg L−1, pH = 4, Dos = 0.02 g/50 mL and T = 303.15 K), outperforming most of the reported adsorbents. In the study of binary systems, we found that the adsorbent exhibited effective co-adsorption capacity, and the differential competitive relationship between two ions was regulated by complex factors. Detailed characterizations revealed the adsorption mechanism, which involved physical adsorption, electrostatic attraction, ion exchange, complexation, and redox reaction. Moreover, the adsorbent maintained high desorption and adsorption efficiency for both ions over eight cycles thanks to strong protonation, Ca2+’s chelation and PANI’s reversibility. This research not only provides a new method for improving gel reusability, but also offers insights for ions co-adsorption study.

Sorption of Soil Carbon Dioxide by Biochar and Engineered Porous Carbons.

CO2 is 45 to 50 times more concentrated in soil than in air, resulting in global diffusive fluxes that outpace fossil fuel combustion by an order of magnitude. Despite the scale of soil CO2 emissions, soil-based climate change mitigation strategies are underdeveloped. Existing approaches, such as enhanced weathering and sustainable land management, show promise but continue to face deployment barriers. We introduce an alternative approach: the use of solid adsorbents to directly capture CO2 in soils. Biomass-derived adsorbents could exploit favorable soil CO2 adsorption thermodynamics while also sequestering solid carbon. Despite this potential, previous study of porous carbon CO2 adsorption is mostly limited to single-component measurements and conditions irrelevant to soil. Here, we probe sorption under simplified soil conditions (0.2 to 3% CO2 in balance air at ambient temperature and pressure) and provide physical and chemical characterization data to correlate material properties to sorption performance. We show that minimally engineered pyrogenic carbons exhibit CO2 sorption capacities comparable to or greater than those of advanced sorbent materials. Compared to textural features, sorbent carbon bond morphology substantially influences low-pressure CO2 adsorption. Our findings enhance understanding of gas adsorption on porous carbons and inform the development of effective soil-based climate change mitigation approaches.

Why does CaX zeolite have such a high CO2 capture capacity and how is it affected by water?

CO2 capture is important in solving one of the major current environmental problems, namely global warming. Among the different approaches, adsorption is considered the most promising and CaX zeolite is one of the materials with the highest capacity. However, the knowledge on the mechanism of its interaction with CO2 is still not complete which hinders further optimization. In this work we report the results of a combined study of CO2 adsorption on a CaX zeolite by in-situ FTIR spectroscopy, adsorption measurements and DFT calculations. It was found that at ambient temperature CO2 initially forms linear Ca2+−OCO species which, with increasing equilibrium pressure, are first converted to Ca2+(CO2)2 and then to Ca2+(CO2)3 species. This is the reason for the very high CO2 adsorption capacity of the material. Because of the practical importance, the effect of H2O on the processes was also studied. Water suppress CO2 adsorption but the effect is softened by the formation of mixed ligand Ca2+(CO2)x(H2O)y complexes (x + y = 2 or 3). In agreement with the spectroscopic results it was found that the adsorption capacity of the material increases with the rise of activation temperature up to 673 K due to dehydration. Its value, 22.2 wt% at 273 K and 490 mbar, is among the highest values reported in the literature at similar conditions.

Adsorption and Diffusion Properties of Functionalized MOFs for CO2 Capture: A Combination of Molecular Dynamics Simulation and Density Functional Theory Calculation.

The capture of carbon dioxide (CO2) from fuel gases is a significant method to solve the global warming problem. Metal-organic frameworks (MOFs) are considered to be promising porous materials and have shown great potential for CO2 adsorption and separation applications. However, the adsorption and diffusion mechanisms of CO2 in functionalized MOFs from the perspective of binding energies are still not clear. Actually, the adsorption and diffusion mechanisms can be revealed more intuitively by the binding energies of CO2 with the functionalized MOFs. In this work, a combination of molecular dynamics simulation and density functional theory calculation was performed to study CO2 adsorption and diffusion mechanisms in five different functionalized isoreticular MOFs (IRMOF-1 through -5), considering the influence of functionalized linkers on the adsorption capacity of functionalized MOFs. The results show that the CO2 uptake is determined by two elements: the binding energy and porosity of MOFs. The porosity of the MOFs plays a dominant role in IRMOF-5, resulting in the lowest level of CO2 uptake. The potential of mean force (PMF) of CO2 is strongest at the CO2/functionalized MOFs interface, which is consistent with the maximum CO2 density distribution at the interface. IRMOF-3 with the functionalized linker -NH2 shows the highest CO2 uptake due to the higher porosity and binding energy. Although IRMOF-5 with the functionalized linker -OC5H11 exhibits the lowest diffusivity of CO2 and the highest binding energy, it shows the lowest CO2 uptake. Accordingly, among the five simulated functionalized MOFs, IRMOF-3 is an excellent CO2 adsorbent and IRMOF-5 can be used to separate CO2 from other gases, which will be helpful for the designing of CO2 capture devices. This work will contribute to the design and screening of materials for CO2 adsorption and separation in practical applications.

Kinetic and mechanistic study of CO2 adsorption on activated hydrochars

Four activated hydrochars (AHCs) were obtained by hydrothermal carbonization of pine sawdust followed by physical and chemical activation in mild conditions. The effects of the activating agents on the porous structure of AHCs were analysed using nitrogen adsorption isotherms. Their CO2 adsorption capacity was assessed by means of carbon dioxide isotherms at 25 and 50 ºC and thermogravimetry, and compared with a commercial activated carbon (AC). SBET values greater than 2000 m2/g were obtained. A narrow micropore volume of 0.392 cm3/g was obtained for the hydrochar activated with KHCO3. The highest CO2 uptake of 3.3 mmol/g (145.2 mg/g) was obtained at room temperature (25 ºC) for the hydrochar activated with KHCO3. Three kinetic models (pseudo-first, pseudo-second and fractional order Avrami’s models) were used to examine the rate parameters of CO2 uptake, with Avrami’s model giving the most accurate prediction of CO2 adsorption. The intraparticle diffusion model and Boyd’s film-diffusion model were applied to identify the CO2 adsorption mechanism.

New porous amine-functionalized biochar-based desiccated coconut waste as efficient CO2 adsorbents.

Climate change caused by the greenhouse gases CO2 remains a topic of global concern. To mitigate the excessive levels of anthrophonic CO2 in the atmosphere, CO2capture methods have been developed and among these, adsorption is an especially promising method. This paper presents a series of amine functionalized biochar obtained from desiccated coconut waste (amine-biochar@DCW) for use as CO2 adsorbent. They are ethylenediamine-functionalized biochar@DCW (EDA-biochar@DCW), diethylenetriamine-functionalized biochar@DCW (DETA-biochar@DCW), triethylenetetramine-functionalized biochar@DCW (TETA-biochar@DCW), tetraethylenepentamine-functionalized biochar@DCW (TEPA-biochar@DCW), and pentaethylenehexamine-functionalized biochar@DCW (PEHA-biochar@DCW). The adsorbents were obtained through amine functionalization of biochar and they are characterized using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectroscopy, Brunauer-Emmett-Teller (BET), and thermogravimetric analysis (TGA). The CO2 adsorption study was conducted isothermally and using a thermogravimetric analyzer. From the results of the characterization analyses, a series of amine-biochar@DCW adsorbents had larger specific surface area in the range of 16.2 m2/g-37.1 m2/g as compare to surface area of pristine DCW (1.34 m2/g). Furthermore, the results showed an increase in C and N contents as well as the appearance of NH stretching, NH bending, CN stretching, and CN bending, suggesting the presence of amine on the surface of biochar@DCW. The CO2adsorption experiment shows that among the amine modified biochar adsorbents, TETA-biochar@DCW has the highest CO2adsorption capacity (61.78mg/g) when using a mass ratio (m:m) of biochar@DCW:TETA (1:2). The adsorption kinetics on the TETA-biochar@DCWwas best fitted by the pseudo-second model (R2 = 0.9998), suggesting the adsorption process occurs through chemisorption. Additionally, TETA-biochar@DCW was found to have high selectivity toward CO2 gas and good reusability even after five CO2adsorption-desorption cycles. The results demonstrate the potential of novel CO2 adsorbents based on amine functionalized on desiccated coconut waste biochar.

Basic Properties of ZnO, Ga2O3, and MgO—Quantitative IR Studies

In our previous study, we elaborated a method of determination of concentrations of the basic sites O2− and OH− in a quantitative IR study of CO2 adsorption. Previous adsorption studies or TPD experiments only provided the total basicity without distinguishing between O2− and OH−. In this study, we determined the concentration of O2− and OH− on ZnO, Ga2O3, and MgO surfaces. The basicity of ZnO and MgO was found to be significantly higher than that of Ga2O3. The surface of ZnO was rich in O2−, the contribution of OH− was very small, and the Ga2O3 surface contained mainly OH−. For MgO, the contribution of O2− and OH− was comparable. According to the IR results, only a small fraction of all surface hydroxyls were sufficiently basic to react with CO2. The partial dehydroxylation changed the proportion of the concentrations of O2− and OH− on the oxides. We also elaborated upon a new method to determine the total concentration of basic sites via CO2 desorption monitored using IR. For all the oxides, we studied the sum of the concentrations of O2− and OH−, as determined in our quantitative IR studies, to find whether they were comparable with the total basicity determined in the desorption experiments.

CO oxidation reactions on 3-d single metal atom catalysts/MgO(100).

The present work deals with a comprehensive computational theoretical study of the molecular CO and O2 adsorption on 3d single atoms (M/MgO(100)). The study is based on the chemical elements of the 3d row, as they represent an economic advantage compared with the so-called noble metals. The present study has been performed employing density functional theory calculations. Through the representation of the metastable states, we perform a synergetic analysis of the CO oxidation reaction to find trends that suggest the possible use of new candidates such as Ni/MgO(100) or Cu/MgO(100) single-atom catalysts, for this type of redox reaction. We found that Ni and Cu produce energetically viable CO to CO2 reactions. Ni and Cu atoms show the greatest diffusion barrier and are the best candidates due to their low sintering capability. The energetic and electronic properties of the single Cu and Ni atoms on MgO (100) give them the best characteristics to help in the CO oxidation process.

Nanoplasmonic sensing to study CO and oxygen adsorption and CO oxidation on size-selected Pt10 clusters.

The adsorption of CO and oxygen and CO oxidation on size-selected Pt10 clusters were studied by indirect nanoplasmonic sensing (INPS) in the pressure range of 1-100 Pa at T = 418 K. CO adsorption was reversible, inducing a blue-shift in the localised surface plasmon resonance (LSPR) response, regardless of the initial CO pressure. We observe a plateau at approximately Δλ = -0.1 nm at PCO > 2.7 Pa, indicating saturation of CO adsorption on Pt10 clusters. Oxygen induces both chemisorption and oxidation of Pt10 clusters until a regime is reached where Δλmax remains positive and constant, showing that the Pt10 clusters are completely oxidised. CO oxidation at different molar fractions is also followed by INPS. All results are discussed in relation to our previous works on 3 nm Pt nanocubes [B. Demirdjian, I. Ozerov, F. Bedu, A. Ranguis and C. R. Henry, ACS Omega, 2021, 6, 13398-13405]. The study demonstrates the suitability of INPS towards the understanding of the nature and function of matter in the largely unexplored subnanometer size regime where properties can often dramatically change when altering the particle size by a single atom.

Computationally aided design of defect-appended aliphatic amines for CO2 activation within UiO-66.

The introduction of aliphatic amine groups in metal-organic frameworks (MOFs) can improve their ability to capture CO2 at low pressures, driven by chemisorptive formation of C-N bonds. Understanding the chemistry of amine-CO2 interaction within the confined porous space in MOFs is key to design and develop effective CO2 adsorbents. Here, we report a computational study of CO2 adsorption and subsequent formation of carbamic acid within defective UiO-66 functionalised with a series of four amino acids of varying aliphatic chain length (glycine, beta-alanine, gamma-aminobutyric acid and 5-aminovaleric acid). Periodic density functional theory (DFT) calculations suggest that CO2 can be activated by the aliphatic amines only when they are sufficiently close to each other to form hydrogen bonds and stabilise the adduct with CO2, a condition met only by UiO-66 functionalised with gamma-aminobutyric acid and 5-aminovaleric acid. The proposed mechanism involves the formation of a carbamate zwitterionic intermediate, which evolves via a simultaneous double hydrogen transfer with a proximal amine group to a carbamic acid. For the 5-aminovaleric acid case, it is suggested that even the functionalisation of just 16% of the available defective sites can be sufficient to form the CO2-amine adduct. Finally, we also investigate the effect of a possible protonation of the amine groups by the hydroxyl groups in the clusters, finding that this could lead to even more favourable interaction with CO2.

Efficient CO2 fixation under atmospheric pressure using a metal- and halide-free heterogeneous catalyst

Pyrimidine based polymers are reported for CO2 adsorption studies. 1,3,5-triaminopyrimidine-based polymer using cheap linker terephthaldehyde is design and employed for the metal- and halide-free carbon dioxide cycloaddition reaction with epoxides.

CO2 adsorption studies on spherical carbon derived from resorcinol-formaldehyde resin and sugars

A highly porous spherical carbon material produced from resorcinol-formaldehyde resin and sugars was applied as an efficient CO2 sorbent. The effect of the modification with different sugars on the physicochemical properties of the obtained materials was investigated. As a result, very efficient CO2 adsorbents have been obtained. Produced materials expressed high CO2 uptake values, reaching 6.79 mmol/g at 0 oC and 1 atm for the sample modified with xylitol. In addition, the selectivity of the sugar modified samples towards CO2 has been significantly improved in comparison to the reference resorcinol-formaldehyde resin derived sample. The incorporation of sugars resulted in changes in the crystallographic structure of the samples leading to obtaining more disordered carbon materials.