ORGANIC-FUNCTIONALIZED MOLECULAR-SIEVES AS SHAPE-SELECTIVE CATALYSTS

Zeolites and related crystalline molecular sieves can possess catalyti cally active acid sites, as well as uniformly sized and shaped pores a nd voids, that allow for their industrial use as shape-selective catal ysts(1). Some catalytic reactions that are not mediated by acids (such as oxidation) have also been shown to occur in zeolites in a shape-se lective manner(2), but the diversity in active sites in these material s remains restricted. For mesoporous materials(3), the diversity in ca talytic activity has been broadened by grafting organosilanes that con tain organic functional groups onto the internal pore surfaces(4-6) or by incorporating them into the structure during the synthesis process (7-12). The former approach has not proven straightforward for micropo rous zeolites because a large fraction of the grafted functional group s become attached instead to the exterior surfaces of the crystal, the re there is no shape selectivity(13). The synthesis of zeolites and mo lecular sieves using organosilanes as structure-directing agents has b een accomplished(14),(15), but the subsequent creation of porosity req uires the complete loss of the organic functional groups. Here we repo rt a new methodology that overcomes these problems and allows the prod uction of microporous molecular sieves containing organic functionalit ies within their pores. During the initial synthesis phase, phenethyl groups covalently tethered to silicon atoms are incorporated into the framework. The external surface-bound functionalities and the structur e-directing agents residing within the intracrystalline spaces are the n removed to create a microporous material. Subsequent sulphonation of the phenyl rings produces intrapore sulphonic acid sites that perform shape-selective catalysis. Different active-site types can be created by attaching other functional groups to the framework silicon, and we therefore expect that our method will lead to the formation of a wide range of shape-selective catalysts.