In Situ CO2-Induced Hydrogels for Enhancing Carbon Sequestration in Saline Aquifers.

Carbon sequestration in saline aquifers underpins global net‑zero emission goals, yet existing CO2 storage capacity remains inadequate, and conventional approaches exhibit limited adaptability to reservoir environment. Here, we introduce smart, injectable soft materials based on CO2‑triggered hydrogels integrated with tailored deep eutectic solvents (DESs) to boost sequestration. The hydrogel forms upon CO2‑triggered protonation of erucamine (a C22‑tailed tertiary amine) within its aqueous dispersion, which promotes electrostatic interactions and hydrophobic self‑assembly. The DESs (choline chloride/polyethylene glycol‑200/boric acid) further enhance system functionality. In situ gelation and flow behavior of these soft materials is validated via visualization and rheology under simulated reservoir conditions (45°C, 10 MPa, 4500 mg·L-1 NaCl). Sequestration assays reveal that a 3.0 wt% erucamine-based hydrogel increases CO2 storage by 31.8% relative to brine; incorporation of 5.0 wt% DESs to form a hybrid hydrogel further elevates storage to 52.9%. Notably, the hydrogel retains structural integrity with no detectable CO2 leakage throughout a 146‑day monitoring period at 45 °C. The improved CO2 sequestration stems from three synergistic mechanisms: erucamine-CO2 reaction, hydrogel physical entrapment, and DESs-promoted solubility. This work establishes a quantifiable and scalable soft material platform that offers a transformative route for advancing CO2 sequestration in saline aquifers.