High-throughput synthesis and catalytic properties of a molecular sieve with 18- and 10-member rings

Abstract

Crystalline molecular sieves with large pores and high adsorption capacities have many potential applications^1,2,3,4. Of these materials, zeolites are of particular interest owing to their stability in a wide range of experimental conditions. An aluminophosphate with very large circular channels⁵ containing 18 oxygen atoms (18-ring channels) has been synthesized, but in the search for large-pore zeolites, most of the materials which have been synthesized up to now contain only 14-ring channels; the synthesis of zeolites with larger ring structures has been believed to be hindered by the low Si-O-Si bond angles available. A silicogaloaluminate (ECR-34) with unidirectional 18-ring channels¹² was recently reported, but exhibited low micropore volume, thus rendering the material less attractive for catalytic applications. Here we report the structure and catalytic activity of the silicogermanate zeolite ITQ-33; this material exhibits straight large pore channels with circular openings of 18-rings along the c axis interconnected by a bidirectional system of 10-ring channels, yielding a structure with very large micropore volume. The conditions for synthesis are easily accessible, but are not typical, and were identified using high-throughput techniques.