A fluoride-free siliceous STW-type zeolite synthesized using a designed organic structure-directing agent.

A pure silica STW zeolite is synthesized with no impurities under a wide range of synthesis conditions with and without fluoride by using easily available 1-methyl-1,5-diazabicyclo[4.3.0]non-5-ene (MDBN) as a template. MDBN having an appropriate size and geometry fits well in the STW cage, leading to its high specificity in structure-directing formation of zeolite STW.