Effect of Micropore Topology on the Structure and Properties of Zeolite Polymer Replicas

Zeolites were used as templates to prepare microporous polymer replicas. Phenolformaldehyde polymers were synthesized and cured within the channel networks of zeolites Y, β, and L. Dissolution of the aluminosilicate framework in aqueous HF yields an organic replica that contains <2% aluminosilicate. The zeolite template exerts important topological effects on the structure and physical properties of the replica. Using zeolites Y and β, which have three-dimensionally interconnected channel structures, the microporosity of the template is reflected in the replica polymer. Pore size distributions are consistent with the predominance of 5-6 Å walls in the parent zeolite. In contrast, complete collapse of the replica, to a give nonporous material, occurs upon removal of the zeolite L template, since the latter has a one-dimensional channel structure. TEM and SEM micrographs also show evidence of collapse in the latter case. Pyrolysis of the zeolite-resin composites at 900°C, and subsequent etching, produces very high surface area, electronically conducting replicas. Under these conditions the zeolite Y replica has markedly lower conductivity than those obtained from β and L, which have straight channels.