(693e) Reaction-Diffusion in Three-Dimensional Fabrication and Sequential Catalysis

Over the last several years, our group has pioneered the use of reaction-diffusion (RD) for micro- and nano- fabrication. In this talk, we present our latest extension of this work, specifically, the use of RD in millimeter scale polymer supports to (i) fabricate three dimensional structures and also (ii) control the products of a one-pot two-step synthesis.

In this context, we have recently succeeded in using RD to fabricate complex structures within porous particles. This so called ?remote? fabrication is performed by first loading polymeric particles with metallic micro- or nano- particles, then immersing the particles in a solution that selectively dissolves the metallic particles. Owing to the diffusive delivery of etchant, using this process we are able to fabricate well defined ?cores? inside of polymer ?shells,? after which the cores can be further modified with galvanic exchange reactions or self-assembled into open lattice crystals.

Likewise, we have also demonstrated that RD can be used to control the distribution of products in one-pot synthesis. In this system, a reactor is loaded with core and shell particles where the shell contains one catalyst and the core contains a second. Thus, as reagents diffuse into the particle they first undergo the reaction catalyzed in the shell then the reaction catalyzed in the core. This method has proven to be highly selective, as demonstrated by nearly 100% conversion of phenylacetylene to 1,4 diphenyl butane in a one-pot synthesis using Cu²⁺ as the shell catalyst and Pd as the core catalyst, which, respectively, catalyze alkyne coupling and hydrogenation.