Design and mechanistic study of hollow SiO ₂ ‐based porous liquids for catalytic CO ₂ cycloaddition

Porous liquids (PLs) are novel materials with permanent pores, showing promise for gas capture and catalysis. Hollow SiO 2 (HS) is commonly used to construct Type I PLs due to its well‐defined structure and functionalizable surface. Here, ionic liquids IL1–5 with catalytic properties were covalently grafted onto HS surfaces via silane coupling, acting as the inner corona. Homogeneous, flowable PLs with dual CO 2 capture and catalytic functions were then formed using weak IL‐solvent interactions. Compared with a reported PL6‐poly(ethylene glycol) 4‐nonylphenyl 3‐sulfopropyl ether potassium salt (PEGS) system (20% styrene oxide [SO] conversion), PL(1–5)‐PEGS achieved 5%–20% higher conversion. The optimal system, PL3‐polyethylene glycol 400, completely converted SO within 8 h at 120°C and 4 bar, and worked for various substrates. Although HS itself is not catalytic, its mesoporous structure enriches CO 2 at the reaction interface, boosting performance over non‐porous references. This study reveals the catalytic mechanism of HS‐based PLs, offering insights for designing high‐performance PL catalysts.