Formation of a three-dimensional mesostructured cobalt smectite during deposition-precipitation functionalization of mesoporous SBA-15

SBA-15 has been functionalized with cobalt by the deposition-precipitation procedure and the obtained samples have been characterized by XRD, N2-sorption, SEM, TPR and ICP-AES. Cobalt stevensite, which is a type of clay material belonging to the smectite group, is formed at the internal surface of the SBA-15 particles during the procedure, without altering the size or shape of the particles. The obtained samples exhibit the XRD peaks characteristic for cobalt stevensite and also the (1 0 0) peak typical for mesoporous materials. Due to the structural re-organization of amorphous silica into crystalline stevensite at the silica surface, the pore walls are contracting. This pore wall contraction causes the micropores in the parent SBA-15 sample to expand, thereby transforming these micropores into mesopores. The obtained cobalt stevensite samples therefore have a three-dimensional structure with interconnected mesopores, which was verified by the observed N2-sorption isotherms of type IVb.