Excessive carbon dioxide (CO₂) emissions have triggered global warming and frequent extreme weather, highlighting the urgency of advancing carbon capture technologies. Although phase change absorbents offer notable benefits for efficient CO₂ capture owing to low-energy regeneration volume enabled by phase separation, rational screening of high-performance ones remains challenging. In this work, three triazole-functionalized ionic liquids (TFILs) were synthesized and blended with organic solvents (as physical solvents or phase-separation agents) to develop novel TFIL absorbents for CO₂ capture. When the mass ratio of the TFIL [Emmim][Triz] to DMSO was 6 : 4, the absorbent showed a CO₂ capacity of 0.121 g CO₂ (g absorbent)⁻¹ at 40 ℃ and 1 bar, with the CO₂-rich phase accounting for 98.5% of the total CO₂ capacity and 53.85% of the total volume, and its regeneration energy consumption was only 1.12 GJ (t CO₂)⁻¹—70% lower than that of the conventional 30 wt% MEA solution. Mechanistic studies revealed that [Emmim][Triz] reacts with CO₂ to form highly polar carbamate, and strong intermolecular hydrogen bonding between carbamate molecules lowers their solubility in the solvent, causing self-aggregation into a rich phase, while the DMSO distributes to the upper lean phase. Based on the polarity-driven phase separation mechanism, a phase change criterion for CO₂ absorption by IL absorbents was proposed: phase change occurs when the dipole moment difference between the product and the phase-separating agent exceeds 12.41 D, which provides a quantitative basis for predicting phase separation behaviors in IL systems. This study developed a TFIL absorbent with excellent comprehensive performance for CO₂ capture and presented a strategy for regulating phase separation behaviors of the absorbents.

Carbon dioxide (CO₂), as an abundant and renewable carbon feedstock, holds immense potential for sustainable biomanufacturing. However, natural carbon fixation pathways, such as the Calvin-Benson-Bassham (CBB) cycle and the reverse tricarboxylic acid (rTCA) cycle, suffer from intrinsic limitations, including low catalytic efficiency, high adenosine triphosphate (ATP) consumption, and oxygen sensitivity. Recent advances in synthetic biology and metabolic engineering have pioneered artificial pathways (e.g., the crotonyl-CoA/ethylmalonyl-CoA/hydroxybutyryl-CoA (CETCH) cycle) that bypass central metabolism, achieving higher fixation rates with reduced ATP consumption. Concurrently, photocatalytic and electrocatalytic systems have emerged as complementary strategies to address cofactor dependency and CO₂ activation thermodynamic barriers. This review summarizes breakthroughs in (ⅰ) rational design for CO₂ conversion pathway optimization, (ⅱ) photocatalysis, and (ⅲ) electrocatalysis for CO₂ activation and cofactor regeneration. By integrating these disciplines, synergistic systems achieve unprecedented efficiency in converting CO₂ to Cn compounds (e.g., ethanol, glyoxylate, sugar, and starch) and establish a foundation for scalable carbon-negative biotechnologies. However, challenges remain, including enzyme denaturation under operational stresses, inefficiencies in multi-enzyme cascades due to kinetic mismatches, and the need for sustainable metrics to ensure net-negative carbon footprints. Future research should prioritize material innovation, CO₂ assimilation system integration, and optimization to unlock higher efficiency CO₂ conversion, aligning with global decarbonization goals while producing high-value chemicals.