Amine and Sulfonic Acid Anchored Porous Silica as Recyclable Heterogeneous Catalysts for Ring‐Opening of Oxiranes

Abstract

MCM type mesoporous silica materials can be used as potential catalysts with appropriate functionalization, for increasing selectivity and yield of the desired products. Co‐condensation or post‐synthesis treatment is the most common process of surface functionalization of mesoporous materials for the introduction of catalytic groups to their internal pore surfaces. In this work two different functional moieties were introduced on the surface of mesoporous material; one, a base functional group (3‐aminopropyl)triethoxysilane (APTES) and another, an acid functional group (3‐mercaptopropyl)triethoxysilane (MPTES). The materials were characterized thoroughly by powder XRD, BET, FT‐IR, TGA, NMR, SEM, TEM, etc. The results confirmed successful grafting of both the functional groups. The functionalized materials were tested in ring opening of different oxiranes; and the base functionalized MCM‐48 was found to be catalytically more active than acid functionalized material and was correlated mechanistically. Conversion of morpholine and piperidine with base functionalized material was found to be 93 and 91 %, respectively; and with acid functionalized material, 52 % of conversion of morpholine and 57 % conversion of piperidine was observed. Amine modified mesoporous MCM‐48 and MCM‐41 were found to be totally heterogeneous in nature and the catalysts were reusable up to 4 times without leaching.