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...