Ca-Embedded C2N: an efficient adsorbent for CO2 capture

Efficient CO2 Capture and Separation in MOFs: Effect from Isoreticular Double Interpenetration

Severe CO2 emissions has posed an increasingly alarming threat, motivating the development of efficient CO2 capture materials, one of the key parts of carbon capture, utilization, and storage (CCUS). In this study, a series of metal-organic frameworks (MOFs) named Sc-X (X = S, M, L) were constructed inspired by recorded MOFs, Zn-BPZ-SA and MFU-4l-Li. The corresponding isoreticular double-interpenetrating MOFs (Sc-X-IDI) were subsequently constructed via the introduction of isoreticular double interpenetration. Grand canonical Monte Carlo (GCMC) simulations were adopted at 298 K and 0.1-1.0 bar to comprehensively evaluate the CO2 capture and separation performances in Sc-X and Sc-X-IDI, with gas distribution, isothermal adsorption heat (Qst), and van der Waals (vdW)/Coulomb interactions. It is showed that isoreticular double interpenetration significantly improved the interactions between adsorbed gases and frameworks by precisely modulating pore sizes, particularly observed in Sc-M and Sc-M-IDI. Specifically, the Qst and Coulomb interactions exhibited a substantial increase, rising from 28.38 and 22.19 kJ mol-1 in Sc-M to 43.52 and 38.04 kJ mol-1 in Sc-M-IDI, respectively, at 298 K and 1.0 bar. Besides, the selectivity of CO2 over CH4/N2 was enhanced from 55.36/107.28 in Sc-M to 3308.61/7021.48 in Sc-M-IDI. However, the CO2 capture capacity is significantly influenced by the pore size. Sc-M, with a favorable pore size, exhibits the highest capture capacity of 15.86 mmol g-1 at 298 K and 1.0 bar. This study elucidated the impact of isoreticular double interpenetration on the CO2 capture performance in MOFs.

Unveiling the intrinsic role of water in the catalytic cycle of formaldehyde oxidation: a comprehensive study integrating density functional theory and microkinetic analysis

Previous research is predominantly in consensus on the reaction mechanism between formaldehyde (HCHO) and oxygen (O2) over catalysts. However, water vapor (H2O) always remains present during the reaction, and the intrinsic role of H2O in the oxidation of HCHO still needs to be fully understood. In this study, a single-atom catalyst, Al-doped C2N substrate, Al1/C2N, can be adopted as an example to investigate the relationship and interaction among O2, H2O, and HCHO. Density functional theory (DFT) calculations and microkinetic simulations were carried out to interpret the enhancement mechanism of H2O on HCHO oxidation over Al1/C2N. The outcome demonstrates that H2O directly breaks down a surface hydroxyl group on Al1/C2N, considerably lowering the energy required to form crucial intermediates, thus promoting oxidation. Without H2O, Al1/C2N cannot effectively oxidize HCHO at ambient temperature. During oxidation, H2O takes the major catalytic responsibility, delaying the entrance of O2 into the reaction, which is not only the product but also the crucial reactant to initiate catalysis, thereby sustaining the catalytic cycle. Moreover, this study predicts the catalytic behavior at various temperatures and presents feasible recommendations for regulating the reaction rates. The oxidation mechanism of HCHO is explained at the molecular level in this study, emphasizing the intrinsic role of water on Al1/C2N, which fills in the relevant studies for HCHO oxidation on two-dimensional carbon materials.

Metal ion-decorated hexasilaprismane and its derivative as a molecular container for the separation of CO2 from flue gas molecules: a computational study

The electronic structure of hexasilaprismane (HSP) was examined with different computational techniques to elucidate the bonding features and the electrostatic surface potential of HSP. The carbon dioxide adsorption and separation capacities of metal-ion-decorated hexasilaprismane (HSP) were examined with DFT and CBS-QB3. Furthermore, the 1,2,3,4,5,6-hexaphenylprismasilane (HPPS) molecule was examined for its binding with metal ions and gas adsorption capacity. The Mg²⁺ ion complexed HPPS molecule adsorbs 15CO₂ molecules with an average binding free energy of -0.98 eV per molecule. The calculated gravimetric densities of 45.1 and 48.4 wt% show that these systems can be employed for CO₂ capture. The substantial difference in the affinity of the designed systems for CO₂ gas molecules compared to N₂ and CH₄ molecules show the potential of the systems for CO₂ separation from N₂ and CH₄ gas molecules.

An in silico study of the selective adsorption and separation of CO2 from a flue gas mixture (CH4, CO2, N2) by ZnLi5+ clusters

Due to the increasing concentration of CO₂ in the atmosphere and its negative effect on the environment, selective adsorption of CO₂ from flue gas has become significantly important. In this study, we have considered a Zn-doped lithium cluster, ZnLi₅⁺ cluster, featuring a planar pentacoordinate Zn centre, as a potential candidate for selective CO₂ capture and separation from a flue gas mixture (CH₄, CO₂, N₂). The binding energy calculation and non-covalent interaction study showed that CO₂ molecules bind relatively strongly as compared to N₂ and CH₄ molecules. The metal cluster can bind five CO₂, five CH₄, and four N₂ molecules with average binding energies of -9.2, -4.4, and -6.1 kcal mol^-1, respectively. Decomposition of the binding energy through symmetry-adapted perturbation theory analysis reveals that the electrostatic component plays a major role. The cationic cluster may be a promising candidate for selective CO₂ capture and can be used as a pollution-controlling agent. The calculated adsorption energy of H₂S is quite closer to that of CO₂, suggesting competitive adsorption between CO₂ and H₂S. The adsorption energies of H₂O and NH₃ are higher compared to CO₂, indicating that these gases may be a potential threat to CO₂ capture.

Adsorption mechanisms of different toxic molecular gases on intrinsic C2N and Ti-C2N-V monolayer: a DFT study

Recently, the excessive emission of chemical toxic gases such as nitrogen trifluoride (NF₃), ammonia (NH₃), phosgene (COCL₂), and benzene (C₆H₆) has caused serious environmental problems. Adsorption of these chemical toxic gas molecules is a promising method to reduce environmental pollution. In this work, density functional theory (DFT) calculations are used to investigate the adsorption properties of these chemical toxic molecules on intrinsic C₂N and Ti-C₂N_-V monolayer. The results show that NF₃, NH₃, C₆H₆, and COCL₂ can all be adsorbed to the intrinsic C₂N monolayer with weak adsorption energy, while the adsorption properties of these gas molecules were greatly improved after doping Ti atom. The adsorption energy of NH₃, C₆H₆, COCL₂, and NF₃ increased from - 0.585, - 0.432, - 0.633, and - 0.362 eV to - 2.214, - 1.699, - 1.822, and - 0.799 eV, respectively, which increased by 2 ~ 4 times compared with that before doping. Besides, the results of the electron distribution, work function, the total density of states (TDOS), and the partial density of states (PDOS) analysis indicate that the doped Ti atom can be used as a bridge to connect the adsorbed molecules with the C₂N_-V monolayer, strengthen their interaction, and significantly improve the adsorption capacity. Therefore, Ti-doped C₂N_-V (Ti-C₂N_-V) monolayer is a promising adsorbent for the enrichment and utilization of harmful gases.

Tuning the electronic, magnetic, and sensing properties of a single atom embedded microporous C3N6 monolayer towards XO2 (X = C, N, S) gases

2D carbon nitride frameworks have received a lot of attention due to their high potential in many applications, such as gas sensing.

Computational Study on Metal-Ion-Decorated Prismane Molecules for Selective Adsorption of CO2 from Flue Gas Mixtures

Selective adsorption of CO₂ from flue gas is extremely significant because of its increasing concentration in air and its deleterious effect on the environment. In this work, we have explored metal-ion-bound prismane molecules for selective CO₂ adsorption from the flue gas mixture. The Ca²⁺-bound prismane complex exhibits superior CO₂ selectivity and adsorption capacity. The calculated binding energy and molecular electrostatic potential (MESP) analysis showed that the rectangular face of prismane binds strongly with metal ions as compared to its triangular face. The CBS-QB3 and density functional theory-based functional M06-2X/6-311+G(d) calculations show that the prismane molecule can bind to one Li⁺, K⁺, Mg²⁺, and Ca²⁺ ion with favorable binding energy. The metal-ion-bound prismane complexes have been examined for their CO₂, N₂, and CH₄ adsorption capacity. Prismane-Ca²⁺ can bind with six CO₂ molecules strongly with an average binding energy of -18.1 kcal/mole as compared to six N₂ (-12.6) and five CH₄ (-13.4) gas molecules. The gravimetric density calculated for the CO₂-adsorbed prismane-Ca²⁺ complex has been found to be 69.1 wt %. The discrete hydrocarbon structure for selective separation of CO₂ is rare in the literature and can have potential applications for cost-effective CO₂ capture from the flue gas mixture.

Modeling of Si-B-N Sheets and Derivatives as a Potential Sorbent Material for the Adsorption of Li+ Ion and CO2 Gas Molecule

In the present exploration, a few Si-B-N derivatives are derived to adsorb Li ions and CO₂ gas molecules for the potential application of metal-air batteries. The newly derived structure's bond lengths are as follows: Si=Si, 2.2 Å; Si-B, 1.9 Å; Si-N, 1.7 Å; and B-N, 1.4 Å, consistent with the experimental results of relevant structures. The stability of the newly derived structures is examined by the atom-centered density propagation study by varying the temperature from 270 to 400 K, and no structural variations are observed throughout the dynamics. Li adsorption on the Si₄B₂ ring has the maximum binding energy of -3.9 eV, and the result is consistent with the previous results. The rings with the 2:1 silicon-boron ratio provide strong adsorption for Li atoms. The calculated maximum electromotive force of the newly derived sheets is 0.56 V with the maximum theoretical density of 783 Wh/kg. Similarly, the maximum adsorption of CO₂ on the sheet is -0.106 eV, which is considerably higher than that on graphene and its derivatives. CO₂ adsorption has been carried out in the presence of water molecules to investigate the change in CO₂ adsorption with the moisture (water) content, and the results show no significant change in the adsorption of CO₂ with moisture. However, water has a strong interaction with the maximum interaction energy of -0.72 eV. Further, to explore the potential ability of the sheets, each sheet's edges are examined as hydrogen storage expedient and the surface as an artificial photosynthesis platform. The Si₄B₂ ring is more favorable for the adsorption of H atom with the chemisorption of -7.138 eV. Similarly, all of the major UV-absorption spectral peaks fall between 450 and 800 nm, which shows that the sheet can be used as an artificial photosynthesis platform.

C2N: an excellent catalyst for the hydrogen evolution reaction

Based on first-principles calculations, we study the hydrogen evolution reaction (HER) on metal-free C₂N and make efforts to improve its catalytic performance.