Uniform platinum nanoparticles are deposited on porous carbon supports using a polymeric precursor method. The presented approach has a high potential since hydrophilic and hydrophobic carbon supports are homogeneously impregnated without any preliminary treatment. The platinum nanoparticles on porous carbon composites show a high catalytic activity in the complete detoxification of formaldehyde. Catalysts with platinum loading as low as 0.75 wt.% enable a complete conversion of 700 ppm formaldehyde into carbon dioxide at a relative humidity up to 60% at room temperature. We assign this remarkable catalytic acitivty to a symbiotic effect of the platinum nanoparticles with the carbon support in terms of an oversolubility of formaldehyde in water confined in the pores of the support material.