The efficient and selective conversion of CO₂as a sustainable C₁resource into valuable chemicals and energy-related products through catalysis is reviewed.

Carbon dioxide chemistry (in particular, capture and conversion) has attracted much attention from the scientific community due to global warming associated with positive carbon accumulation. The most widely used chemical absorption technique for carbon capture and storage/sequestration (CCS) would be essentially adopting amino-containing absorbents through formation of C–N bond in terms of mechanistic consideration. However, extensive energy input in desorption and compression process would be a crucial barrier to realize practical CCS. On the other hand, CO₂ is very attractive as an environmentally friendly feedstock to replace the hazardous phosgene route for making commodity chemicals, fuels, and materials from a standpoint of green chemistry, whereas the reactions involving CO₂ are commonly carried out at high pressure, which may not be economically suitable and also pose safety concerns. The challenge is to develop catalysts that are capable of activating CO₂ under low pressure (preferably at 1 atm), and thus incorporating CO₂ into organic molecules catalytically. We have proposed a carbon capture and utilization (CCU) strategy as an alternative approach to addressing the energy penalty problem in CCS. The essence of our strategy is to use captured CO₂, also considered as the activated form of CO₂, which could render this system suitable for accomplishing chemical transformation of CO₂ under low pressure to avoid an additional desorption step. Indeed, CO₂ could be activated through the formation of carbamate/alkyl carbonate with Lewis basic nitrogen species. In this review, we would like to discuss and update advances on CCU, particularly C–N bond formation with the production of oxazolidinones, quinazolines, carbamates, isocyanates and polyurethanes by using CO₂ as C1 feedstock, and CO₂ capture by amino-containing absorbents, including conventional aqueous solution of amine, chilled ammonia, amino-functionalized ionic liquids and solid absorbents such as amino-functionalized silica, carbon, polymers and resin, presumably leading to CO₂'s activation and thus subsequent conversion through C–N bond formation pathway.

Ionic liquids (ILs), a kind of novel green medium composed entirely of cations and anions, have attracted considerable attention due to their unique properties such as non-volatility, tunable polarity, high stability and so on. In this article, the latest progress on the absorption and subsequent conversion of CO₂ by using ILs as absorbents, catalysts or promoters will be summarized. The chemical absorption performance of ILs, especially task-specific ionic liquids (TSILs) such as amino-functionalized ILs, superbase-derived protic ILs has been systematically illustrated. Although significant advances have been made, extensive energy input in the desorption process to recover absorbents would still be a crucial barrier to realizing practical carbon capture and sequestration (CCS). On the other hand, efficient applications of CO₂ in the synthesis of valuable compounds such as organic carbonates, urea derivatives, oxazolidinones and formic acid can also be promoted by employing TSILs as catalysts/reaction media. We anticipate that an integration of chemical capture of CO₂ with its utilization, a so-called CO₂ capture and utilization (CCU) protocol would be an ideal strategy to solve the energy penalty problem in common CCS without the need for additional heat desorption. The essence of this CCU concept is to use TSILs for CO₂ capture and substantial activation, which could allow catalytic transformation of CO₂ to be accomplished smoothly under low pressure (ideally at 1 atm).

Carbon dioxide, a greenhouse gas mainly from the consumption of fossil fuel, is regarded as an attractive feedstock in view of synthetic chemistry. Great efforts have been devoted to developing catalytic processes for converting CO₂ into value-added compounds with reduced carbon footprint. Among versatile applications in organic synthesis, CO₂ can serve as a promising raw material for fuel production, especially methanol. ‘Coming from fuel and returning to fuel’ is an appealing objective in terms of sustainable development associated with circumventing the energy shortage and CO₂ issue. To date, metal complexes and organocatalysts for CO₂ hydrogenation to methanol have been developed along with the reaction mechanistic insight. Understanding the interaction of active catalytic species with CO₂ or hydrogen could account for development of efficient homogeneous catalysts. In this context, homogeneous catalytic hydrogenation of CO₂ and its derivatives into methanol is highlighted in this article in combination with mechanistic understanding on a molecular level.