an improved catalyst is provided which is useful in hydroformylation reactions comprising a rhodium carbonyl complex and a polybenzimidazole fiber support wherein under hydroformylation conditions the rhodium carbonyl complex forms a catalytically active polybenzimidazole complex with the benzimidazole units of the polybenzimidazole fiber surface acting as donor ligands for the rhodium carbonyl complex . this fiber supported catalyst may be readily separated from the products of the hydroformylation reaction by simple filtration .