Morphology Control and Catalytic Application of Mesoporous Structures Prepared by Sol-Gel Processing

摘要

A highly ordered mesoporous molecular sieve was synthesized in the acidic tetraethoxy-orthosilane (TEOS) sol-gel solution containing an amphiphilic triblock copolymer of poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) (EO_(20)PO_(70)EO_(20), PEO 30 wt %) as structure directing agent. X-ray diffraction (XRD) and transmission electron microscopy (TEM) measurement showed that increasing the amount of (EO_(20)PO_(70)EO_(20) with respect to TEOS resulted in a variety of morphology of the internal pore structure. At a molar ratio of TEOS to (EO_(20)PO_(70)EO_(20) of about 40, the mesostructure with a long range hexagonal columnar ordering, denoted as M40, was synthesized. One synthesized with a molar ratio of TEOS to (EO_(20)PO_(70)EO_(20) of 60 displayed a co-continuous morphology, similar to the gyroid structure observed in spherical block copolymers. Palladium was successfully immobilized on M40 to be applied as a catalyst with a high level of enantioselectivity in the asymmetric hydrogenation of *-keto acids to the corresponding amino acids.