Guest/host relationships in zeolite synthesis: ring-substituted piperidines and the remarkable adamantane mimicry by 1-azonio spiro [5.5] undecanes

This paper explores the contribution to high silica zeolite syntheses based upon derivatives of a six-ring heterocycle, piperidine. The zeolite product selectivity can be rationalized in terms of the type and location of ring substitution in the derivatives studied as structure-directing agents (SDAs) in zeolite crystal growth. A number of new zeolite products were found as the substitution leads to spatially larger molecules. The pure phase MEL was produced by one very specific SDA. As well as the synthesis studies presented, a select group of derivatives built around the azaspiro [5.5] undecane architecture were also studied as to their hydrophobic transfer from water to chloroform during solvent partitioning studies. One surprising discovery was that a single spiro derivative produced five different zeolite products over a range of synthesis conditions, and these five zeolites were initially encountered in studies with a single adamantyl derivative. Attempts were made via molecular modeling to determine why these two disparate SDAs yield almost the same zeolite product selectivities. (C) 1998 Elsevier Science B.V. All rights reserved.