The aqueous biphasic hydroformylation of 1-octene catalyzed by cobalt complex of the water-soluble ligand trisulfonated tris(biphenyl)phosphine (BiphTS) was investigated in the absence and presence of various mass transfer promoters (co-solvents, surfactants, cyclodextrins and activated carbon). In the presence of cetyltrimethylammonium bromide, methylated beta-cyclodextrin or activated carbon, the Co/BiphTS system allowed the hydroformylation of 1-octene with high conversion (92-95%) and aldehydes selectivity (85-90%). Moreover, the catalytic system could be easily reused in the presence of activated carbon as a mass-transfer promoter. In all cases, the conversion and the aldehydes selectivity were found to depend strongly on the ligand/cobalt ratio. (C) 2011 Elsevier B.V. All rights reserved.