A catalyst composition comprising a polymer functionalized with a ligand for binding a transition metal containing compound to form a transition metal complex, wherein said functionalized polymer has a number average molecular weight of about 5,000 to 30,000 g/mol and a polydispersity index of about 1.0 to 2.0. The catalyst is used in a hydroformylation reaction, preferably one in which the liquid phase has been volumetrically expanded with a compressed gas, is readily recyclable using nanofiltration.