Based on the synthesis of a new kind of room temperature ionic liquids, quaternary ammonium alkanesulfonate salts tailed with polyether chain to their alkyl group, a thermoregulated ionic liquid biphase system composed of ILPEG750, n-heptane and toluene was developed. The system was applied in the hydroformylation of 1-dodecene catalyzed by Rh/TPPTS complex. Under the optimum conditions, the conversion of 1-dodecene and yield of aldehyde are 99% and 97%, respectively. In addition, the catalyst could be easily separated from products by phase separation and efficiently recovered. Copyright © 2008 John Wiley & Sons, Ltd.