Cesium-phosphorous-silicon mixed oxide (Cs-P-Si oxide), a typical acid-base bifunctional catalyst, efficiently catalyzes propylene carbonate synthesis from CO2 and propylene oxide under supercritical conditions (8-10 MPa). This catalyst contains no halogens and requires no additional solvents. A portion of the catalyst was eluted into the product solution during catalysis. It was also found that Cs3PO4, one of the species that may be eluted from the Cs-P-Si oxide, is an effective non-halogen homogeneous catalyst. (c) 2005 Elsevier B.V. All rights reserved.