The cycloaddition of CO2 to epoxides proceeds effectively under extremely mild temperatures and pressures by using a bifunctional catalyst system of tetradentate Schiff-base aluminum complexes (SalenAlX) as electrophile in conjunction with polyether-KY complexes as nucleophile. The steric factor of the substituent groups on the aromatic rings of SalenAlX and the nucleophilicity and leaving ability of the anion Y-1 of polyether-KY complexes all have Great effects on the activity of the bifunctional catalyst system. The reaction of CO2 with (S)-propylene oxide in the presence of the SalenAlEt/18-crown-6-K1 catalyst system gives (S)-propylene carbonate in >99% ee with retention of stereochemistry. (C) 2004 Elsevier Inc. All rights reserved.