Cobalt porphyrin covalently bonded to organo modified silica xerogels

► Hybrid materials were synthesized from cobalt porphyrins bonded to organo-modified silica. ► Electronic transitions of the porphyrin depend on the length of the alkyl group attached to the network. ► Total pore volume, pore size, and surface area depend on the alkyl group in the matrix. ► It is possible to design advanced hybrid systems combining porphyrins and organo-substituted alkoxides.