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.