(241a) Dendrimer-Ceramic Composite Membranes for Challenging Separations

We synthesize organic-inorganic composite membranes by decorating the porous surfaces of mesoporous alumina or silica substrates with selective organic molecules. This architecture gives us a degree of simultaneous control over both the chemistry and free volume of the membrane that is difficult to attain with purely polymeric or purely inorganic materials. The mesoporous substrates are either (1) commercially available alumina membranes with pore sizes in the 5 to 10 nm range or (2) custom-synthesized supported cubic mesoporous thin films. Various triazine-based dendritic molecules are covalently grown from the porous membrane surfaces to give the desired chemical functionality. This organic portion of the composite is varied by increasing the number of generations of the dendrimer grown on the surface and by varying the length and functionality of the dendrimer terminating groups, as well as by using different spacer groups between branches. The application focus is on the gas-phase separation of organic molecules from lighter species. The performance of our composite membranes compares very favorably to the best results reported in the literature for purely polymeric membranes.