Adsorption by solid amine adsorbent is a promising technology for decarbonization of flue gas. However, adsorption properties of many solid amine adsorbents need to be enhanced, and it is necessary to further study the CO₂ adsorption mechanism. A novel CO₂ adsorbent with high capacity was obtained by grafting 3-aminopropyltriethoxysilane (APTES) on a micro-mesoporous composite molecular sieve ZSM-5/MCM-48 as the support, and then impregnated with tetraethylenepentamine (TEPA) or polyethyleneimine (PEI). The maximum adsorption capacity of APTES-ZSM-5/MCM-48-TEPA-60 (A-ZM-T60), loaded with 60% (in mass) TEPA, for CO₂ reaches 5.82 mmol·g^-1 at 60 ℃ in 15% (in volume) CO₂. Carbamate, alkyl ammonium carbamate and carbonate are generated during the chemical adsorption, which is dominant for CO₂ adsorption because of the reaction between CO₂ and amino groups on the adsorbent, simultaneously accompanied by weak physical adsorption. All above data confirm that these composites display an outstanding adsorption performance with a bright future for CO₂ capture from flue gas after desulfurization.

Nowadays, we are facing increasingly serious energy and environmental problems, which urgently need more efficient chemical industry technologies to meet the requirements of low cost, high yield and sustainability. Developing efficient catalysts is of great significance for improving production efficiency, expanding economic benefits, optimizing energy structure, and ameliorating industrial structure. Single-atom catalysts (SACs), featuring unique properties arising from their single-atom dispersion on support surface, have demonstrated exceptional activity, selectivity and stability in energy catalysis, environmental catalysis and organic catalysis. Therefore, preparation methods and catalytic mechanisms of SACs have become a hot research topic on the international catalytic community. This review describes three strategies for preparing SACs: bottom-up synthesis, top-down synthesis and quantum dots cross-linking/self-assembly. Specifically, methods such as co-precipitation, immersion, atomic layer deposition, high-temperature atom thermal transfer, and high-temperature pyrolysis are presented in detail. These approaches precisely control the location and distribution of metal atoms, maximizing their utilization and catalytic efficiency. In addition, the challenges and development prospects faced by SACs related to stability, integrated control and industrial scalability are also summarized.

Direct polymerization of CO₂ with diols for synthesis of carbonates represents a sustainable and efficient approach for CO₂ utilization, in which CeO₂ exhibits favorable catalytic properties in the reaction system. In this study, nanometer-sized CeO₂ catalysts were synthesized via a hydrothermal method utilizing NaOH as precipitating agent. The effects of sintering temperatures (500, 600, and 700 ℃) and surfactants (cationic, anionic, and nonionic) on structural and physicochemical properties of CeO₂ were thoroughly investigated. When the sintering temperature was 600 ℃, CeO₂ displayed an optimal crystallinity and a higher concentration of defect sites compared to the other temperatures. The surfactants significantly increased oxygen vacancy concentration on the surface of CeO₂, leading to a maximum CO₂ uptake of 0.532 mmol/g at 25 ℃. Building upon these findings, a series of synthesized CeO₂ catalysts were applied in the one-step synthesis of polycarbonate from CO₂ and diol, resulting in significant improvements in both conversion and selectivity within the reaction system. The results demonstrated that catalytic activities of CeO₂ prepared at various sintering temperatures with different surfactants displayed notable differences. Notably, the CeO₂ catalyst sintered with cetyltrimethylammonium bromide (CTAB) as the surfactant at 600 ℃ exhibited the highest catalytic activity and selectivity, achieving a conversion of 91.0% for 1,6-hexanediol and a selectivity of 76.6% for poly(6-hydroxyhexyl) carbonate. The outstanding catalytic performance of CeO₂ with the high yield can be primarily attributed to its favorable structural characteristics, abundant defect sites, and high CO₂ uptake capacity.

Among all options of carbon neutrality, conversion of CO₂ into valuable chemicals by electrocatalytic reduction exhibit outstanding performance. However, due to the numerous products and complex pathways of CO₂ electrocatalytic reduction, the exact factors affecting the activity of CO₂ electrocatalytic reduction have not yet been identified. In addition, the CO₂ electrocatalytic reduction process is often accompanied by hydrogen evolution reaction (HER). Therefore, it is still challenging to design a catalyst with high selectivity and high activity for specific product. Herein, this study systematically investigated the potential of 3d transition metal-based single-atom catalysts (SACs) positioned at graphene single vacancies (TM@C_SV), as well as double vacancies (TM@C_DV), for the CO₂ reduction reaction (CO₂RR) using first-principles. The exploration encompassed substrate stability, CO₂ adsorption, and the HER as the main competing reaction. Through the careful screening of 20 catalysts formed by Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu and Zn doped graphene defects, several promising catalysts were identified: Sc@C_SV situated on graphene single vacancies, Sc@C_DV and Ti@C_DV situated on graphene double vacancies. They could not only effectively adsorb CO₂ molecules, but also inhibit HER, the main competing reaction. In assessing their performance in CO₂RR, all exhibited selectivity toward HCOOH. Notably, Sc@C_DV demonstrated the best selectivity, requiring the lowest ΔG (0.96 eV) for efficient CO₂ conversion to HCOOH. Electronic structure analysis revealed that Sc@C_DV outperforms due to its optimal balance between ΔG of hydrogenation and the product desorption achieved through a moderate number of active electrons.

Electrochemical reduction of CO₂ to high value-added hydrocarbon fuels and chemicals has emerged as an effective strategy to achieve carbon neutrality. In conventional electrocatalytic powder-coated electrodes fabricated by spraying method, poor contact between electrocatalyst and substrate can severely impact the electrocatalytic activity and stability. Herein, a self-supporting nanotree electrode (Bi@Cu NTs) for efficient electroreduction from CO₂ to formate was structured by combing facile electrodeposition method and galvanic replacement reaction. The advantages of self-supporting nanotree structure including: 1) minimization of the interfacial resistance and improvement of the spatial structure stability; 2) rich active sites and plentiful pore structures. The charge transfer resistant could be effectively reduced while ensuring the stability of the electrode operation. Results demonstrated that the prepared Bi@Cu NTs electrode exhibited outstanding performance for CO₂ conversion in both electrochemical activity and long-term operation stability. In a wide operating potential window from -1.4 to -0.8 V (vs. RHE), the proposed Bi@Cu NTs electrode presented excellent formate selectivity, where the Faradaic efficiency of CO₂-to-formate (FE_Formate) at each operating potential was above 90%. Typically, at -1.2 V, the proposed electrode achieved a high FE_Formate of 97.9% and a current density of 170.6 mA·cm^-2, simultaneously. Meanwhile, the self-supporting Bi@Cu NTs electrode also revealed excellent stability in a long-term operation, as evidenced by maintaining an average FE_Formate of more than 90% and an average current density higher than 110 mA·cm^-2 over 50 h of continuous electrolysis at a controlled potential of -1.0 V without any degradation in performance.