The effect of edge-functionalization on the competitive adsorption of a binary CO2-CH4 mixture in nanoporous carbons (NPCs) has been investigated for the first time by combining density functional theory (DFT) and grand canonical Monte Carlo (GCMC) simulation. Our results show that edge-functionalization has a more positive effect on the single-component adsorption of CO2 than CH4, therefore significantly enhancing the selectivity of CO2 over CH4, in the order of NH2-NPC > COOH-NPC > OH-NPC > H-NPC > NPC at low pressure. The enhanced adsorption originates essentially from the effects of (1) the conducive environment with a large pore size and an effective accessible surface area, (2) the high electronegativity/electropositivity, (3) the strong adsorption energy, and (4) the large electrostatic contribution, due to the inductive effect/direct interaction of the embedded edge-functionalized groups. The larger difference from these effects results in the higher competitive adsorption advantage of CO2 in the binary CO2-CH4 mixture. Temperature has a negative effect on the gas adsorption, but no obvious influence on the electrostatic contribution on selectivity. With the increase of pressure, the selectivity of CO2 over CH4 first decreases sharply and subsequently flattens out to a constant value. This work highlights the potential of edge-functionalized NPCs in competitive adsorption, capture, and separation for the binary CO2-CH4 mixture, and provides an effective and superior alternative strategy in the design and screening of adsorbent materials for carbon capture and storage.

Graphical Abstract:The strategies to enhance CO 2 capture and separation based on the state-of-the-art adsorbent materials have been proposed by topological structure design, chemical doping, chemical functionalization, open metal sites, and electric field, etc. This review will present a constructive way for the design and screening of novel adsorbent materials.Uncontrolled massive CO 2 emission into atmosphere is becoming a huge threat to our global climate and environment. Carbon capture and storage (CCS), starting with the crucial step of CO 2 capture and separation, provides a promising approach to alleviate this issue. The major challenge for CO 2 capture and separation is to explore efficient adsorbent materials with high storage capacity and selectivity. This review firstly summarized the significant advancement in a diversity of state-of-the-art adsorbent materials. Then particular attention was focused on the practical strategies to enhance CO 2 capture and separation based on the current adsorbent materials by topological structure design, chemical doping, chemical functionalization, open metal sites, and electric field, etc. These strategies paved constructive ways for the design and synthesis of novel adsorbent materials. Finally, we gave a perspective view on future directions in the rapidly growing field. Canada) and developing countries (e. g., China) have already participated in CCS (Fig. 1b). Even better, more and more countries are on the way to mitigate CO 2 emissions.CO 2 capture and separation at stationary point source is a great concern step for practical CCS applications. Significant concern on the tremendous scale of coal and gas combustion highlights the importance of the primary process. Long et al. 3,4 provided a comprehensive overview on the possible considerations associated with CO 2 capture in pre-/post-/oxy-fuel combustion processes, with particular attention on the progress in CO 2 capture and separation by virtue of metal organic frameworks (MOFs) as adsorbent materials. One of the greatest challenges in this process is to find excellent adsorbent materials that would be long-term stable. The conventional adsorbent materials are mainly on aqueous amine solutions or chilled ammonia in current industrial application. Alie et al. 5 reported that amine scrubbing, a typical approach to capture CO 2 , has the efficiency up to 98%. However, serious issues still exist for conventional adsorbent materials, such as equipment corrosion, solvent loss, and toxicity, which retard their further applications. 6,7 And, one of the most disadvantages was the high energy input for amine regeneration. Significant work is still needed to identify the promising adsorbent materials so as to overcome these problems. [9][10][11] Ideal adsorbent materials should have high CO 2 adsorption capacity, excellent adsorption selectivity over other gases, and good chemical and mechanical stability. Recently, several groups focused on the study of synthetic methods and performance estimations on the specific clas...

Design of light-absorbent dyes with cheaper, safer, and more sustainable materials is one of the key issues for the future development of dye-sensitized solar cells (DSSCs). We report herein a theoretical investigation on a series of polypyridyl Cu(I)-based complexes with general formula [CuLL 0 ] þ (L and L 0 represent bipyridyl ligands) by density functional theory (DFT) and time-dependent DFT. Molecular geometries, electronic structures, and optical absorption spectra are predicted in both the gas phase and methyl cyanide solution. Our results show that all the [CuLL 0 ] þ derivatives display Cu f bipyridine metal-to-ligand charge transfer absorption spectra in the range of 350-700 nm. Structural optimizations by enhancing π-conjugation and introducing heteroaromatic groups on ancillary ligands lead to upshift of molecular orbital energies, increase in oscillator strength, and red shift of absorption spectra. Compared with Ru(II) sensitizers, polypridyl Cu(I)-based complexes show similar optical properties and improving trend of the DSSCs performance along with the optimizations of structures. The results of this work highlight the point that polypyridyl Cu(I)-based complexes could provide promising sensitizers for efficient next-generation DSSCs.

Single atom catalysts (SACs) are promising electrocatalysts for CO2 reduction reaction (CO2RR), in which the coordination environment plays a crucial role in intrinsic catalytic activity. Taking the regular Fe porphyrin (Fe‐N4 porphyrin) as a probe, the study reveals that the introduction of opposable S atoms into N coordination (Fe‐N2S2 porphyrin) allows for an appropriate electronic structural optimization on active sites. Owing to the additional orbitals around the Fermi level and the abundant Fe dz2 orbital occupation after S substitution, N, S cocoordination can effectively tune SACs and thus facilitating protonation of intermediates during CO2RR. CO2RR mechanisms lead to possible C1 products via two‐, six‐, and eight‐electron pathways are systematically elucidated on Fe‐N4 porphyrin and Fe‐N2S2 porphyrin. Fe‐N4 porphyrin yields the most favorable product of HCOOH with a limiting potential of −0.70 V. Fe‐N2S2 porphyrin exhibits low limiting potentials of −0.38 and −0.40 V for HCOOH and CH3OH, respectively, surpassing those of most Cu‐based catalysts and SACs. Hence, the N, S cocoordination might provide better catalytic environment than regular N coordination for SACs in CO2RR. This work demonstrates Fe‐N2S2 porphyrin as a high‐performance CO2RR catalyst, and highlights N, S cocoordination regulation as an effective approach to fine tune high atomically dispersed electrocatalysts.

The effects of chemical and structural surface heterogeneity on the CH4 adsorption behaviour on microporous carbons have been investigated using a hybrid theoretical approach, including the use of density functional theory (DFT), molecular dynamics (MD), and grand canonical Monte Carlo (GCMC) simulations. Bader charge analysis is first performed to analyze the surface atomic partial charges. The CH4 adsorption densities in defective and functionalized graphite slit pores are lower than that in the perfect pore according to the MD simulations. Finally, the CH4 adsorption isotherms for the perfect, defective and functionalized slit pores are analyzed using the GCMC simulations in combination with the DFT and MD results. For pores with a defective surface, the adsorption capacities decrease; the embedded functional groups decrease the adsorption capacity at low pressure and enhance it at high pressure. Our results demonstrate the significant effects of chemical and structural surface heterogeneity on the CH4 adsorption and provide a systematic approach to understand the gas adsorption behaviour.

CO2 hydrogenation towards COOH is more favorable on perfect CeO2 (111) surface, whereas reductive dissociation of CO2 is predominant on O-defective surface. The O vacancy promotes reductive dissociation of CO2 on O-defective CeO2 (111) surface.

Surface modification by metal doping is an effective treatment technique for improving surface properties for CO reduction. Herein, the effects of doped Pd, Ru, and Cu on the adsorption, activation, and reduction selectivity of CO on CeO(111) were investigated by periodic density functional theory. The doped metals distorted the configuration of a perfect CeO(111) by weakening the adjacent Ce-O bond strength, and Pd doping was beneficial for generating a highly active O vacancy. The analyses of adsorption energy, charge density difference, and density of states confirmed that the doped metals were conducive for enhancing CO adsorption, especially for Cu/CeO(111). The initial reductive dissociation CO → CO* + O* on metal-doped CeO(111) followed the sequence of Cu- > perfect > Pd- > Ru-doped CeO(111); the reductive hydrogenation CO + H → COOH* followed the sequence of Cu- > perfect > Ru- > Pd-doped CeO(111), in which the most competitive route on Cu/CeO(111) was exothermic by 0.52 eV with an energy barrier of 0.16 eV; the reductive hydrogenation CO + H → HCOO* followed the sequence of Ru- > perfect > Pd-doped CeO(111). Energy barrier decomposition analyses were performed to identify the governing factors of bond activation and scission along the initial CO reduction routes. Results of this study provided deep insights into the effect of surface modification on the initial reduction mechanisms of CO on metal-doped CeO(111) surfaces.

First-principles investigations were performed to elucidate the effects of A and X in Ge-based MAGeX3 perovskites (MA = CH3NH3+; X = Cl−, Br−, and I−) and AGeI3 (A = Cs+, CH3NH3+, HC(NH2)2+, CH3C(NH2)2+, and C(NH2)3+) on the photoelectronic properties.