Catalyzed Schiff Base Synthesis over Bifunctionalized Cobalt/ Zinc-Incorporated Mesoporous Silica Nanoparticles under UV Irradiation

A novel series of the Co/Zn-MSN catalysts with Si/Zn molar ratio of 10 and 1, 3, 5 and 7 wt% Cobalt (denoted by CZ-X-MSN) were synthesized using post-synthesis methods. The samples were characterized by XRD, SEM, FTIR, TEM and nitrogen sorption methods. With a constant Si/Zn ratio, the increase of cobalt species from 1 to 7 wt% led to decrease the catalysts surface area from 408 m2g-1 for CZ-1-MSN to 322 m2g-1 for CZ-7-MSN. The catalyst activities were investigated for Schiff base synthesis by the reaction of cyclohexanone with 2,4-dinitrophenylhydrazine under UV irradiation. The activity of the catalysts in the Schiff base synthesis followed the order of Zn-MSN-10 < CZ-1-MSN < CZ-7-MSN < CZ-3-MSN < CZ-5-MSN. The CZ-5-MSN sample exhibited the highest performance with the conversion and selectivity of cyclohexanone to the Schiff base product were 98 and 97%, respectively, under UV light at 298 K for 10 min. The superior catalytic performance of CZ-5-MSN includes high yield, low reaction temperature, short reaction time and friendly environment. This probably was related to stronger metal-support interaction and metals dispersion. This study provides the new perspective on the synthesis of CZ-X-MSN towards an excellent performance of Schiff base structure under UV irradiation.