Four CO2 adducts of carbodicarbenes (CDCs) were first synthesized and structurally characterized by means of NMR spectroscopy, high‐resolution mass spectrometry, and FTIR spectroscopy. The introduction of 13C‐labelled CO2 confirmed the formation of the corresponding carboxylated species. Thermogravimetric analysis (TGA) provided detailed information on their thermal decarboxylation processes. The novel CDC–CO2 adducts were subsequently applied as robust and versatile organocatalysts for the carboxylative cyclization of CO2 with aziridines, epoxides, or propargylic alcohols, affording 2‐oxazolidinones and cyclic carbonates in good to excellent yields (51–99 %) and high functional group tolerance. TGA results together with control experiments indicate that the in situ formed free CDC by decarboxylation of the corresponding CDC–CO2 adducts plays the key role to activate the substrates by its strong Lewis basicity.

The exponentially increasing viscosity of water‐lean CO2 absorbents during carbon capture processes is a critical problem for practical application, owing to its strong correlation with systems’ mass transfer properties, as well as convenience of transportation. In this work, a concise strategy based on structure–viscosity relationships is proposed and applied to construct a series of functionalized ethylenediamines as single‐component absorbents for post‐combustion CO2 capture. These nonaqueous absorbents have outstanding viscosities (50–200 cP, 25 °C) at their maximal CO2 capacities (up to 22 wt % or 4.92 mol kg−1, 1 bar), and are readily regenerated at low temperatures (50–80 °C) under ambient pressure. Additional capture of CO2 through physisorption could also be achieved by operating at high pressures. The CO2 capture and release process is systematically investigated by means of 13C NMR spectroscopy, differential scanning calorimetry (DSC), in situ FTIR analysis, and density functional theory (DFT) calculations, which could provide sufficient spectroscopic details to reveal the ease of reversibility and enable rational interpretation of the absorption mechanism.

CO2 absorption and desorption performance of novel ether-functionalized MEAs under solvent-free condition and their thermodynamic features as well as structure–property relationships are reported.

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Aqueous alkanolamine-based processes currently represent the most mature and widely employed CO2 capture technology. However, extensive energy input and severe equipment corrosion constitute their major and inherent drawbacks due to the involvement of vast amounts of water as the diluent. Water-lean absorbents are proposed to deliver potential benefits, such as higher capacity and enhanced energy efficiency, by abandoning the aqueous solvent or replacing it with organic counterparts. Great efforts have been devoted to the development of CO2 capture protocols under nonaqueous circumstance, but their industrial deployment is still challenged by the exponentially increasing viscosity during operation. In this work, a series of alkoxy-functionalized methylamines have been devised as single-component postcombustion CO2 absorbents under water-lean condition. These nonaqueous amines are capable of reversibly capturing CO2 with low viscosities (48–114 cP at 25 °C and 27–63 cP at 40 °C) at their maximal gravimetric capacities (15–21 wt % at 25 °C and 14–21 wt % at 40 °C). Comprehensive mechanistic studies by means of in situ Fourier transform infrared spectroscopy, density functional theory calculations, and control experiments revealed that the stabilization of sequestered CO2 via intramolecular hydrogen bonding between in situ formed carbamic acid and the flexible alkoxy side chain of the designed amines would play the key role in enhancing both the capacity and flowability. Meanwhile, thermal desorption of the captured CO2 could easily be carried out at a feasible temperature (75 °C) under ambient pressure, and the CO2-saturated absorbents have remained intact at 80 °C for 2 days within a closed system. Furthermore, these novel amines would exhibit considerable physisorption by operating at high-pressure conditions (20 and 30 bar), thanks to the inherent CO2-philicity of the alkoxy functionality. Hence, the integration of enhanced capacity, reduced operating viscosity, and mild regeneration makes such alkoxy-functionalized methylamine-type absorbent a compelling candidate for practical application.

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