Synthesis and Surface Chemistry of Spherical Mesoporous Organic−Inorganic Hybrid Particles with an Integrated Alcohol Functionality on the Pore Surface

Novel mesoporous organic−inorganic spherical hybrid particles are described that contain a 3-hydroxypropyl organic functionality which is integral to the pore surface. The 3-hydroxypropyl hybrid particle is synthesized in three steps starting from a 4:1 (mol/mol) mixture of tetraethoxysilane and [3-(methacryloxy)propyl]trimethoxysilane, where the monomers are polymerized to a poly(organoalkoxysilane) oil, followed by sol−gel reaction to the hybrid silicate bead, which is finally subjected to an alkaline hydrothermal treatment to liberate the alcohol from the ester protecting group. The silicate precursor and final product were characterized by NMR spectroscopy and nitrogen sorption analysis. The heterogeneous surface chemistry of the hybrid's alcohol functionality was explored by running a series of classical alcohol reactions including bromination, esterification (carbamic and carbonic), and etherification (Williamson, epoxide ring opening). The brominated analogue was further converted via cyanation and Grignard couplings. Nuances to the heterogeneous surface chemistry are discussed as well as product characterizations by NMR spectroscopy and combustion analysis. A stability study was further conducted on the 3-hydroxypropyl hybrid silicate using an alkaline resistance test under HPLC packed column conditions. The hybrid material was found to be over 10-fold more stable than a comparable silica gel material. In a second HPLC test, the cyano derivatized hybrid material was found to be more resistant to acid-induced siloxane cleavage vs a comparable (3-cyanopropyl)silane grafted silica gel.