Understanding the Anion‐Templated, OSDA‐Free, Interzeolite Conversion Synthesis of High Silica Zeolite ZK‐5

High silica zeolite ZK‐5 (framework Si/Al=4.8) has been prepared by interzeolite conversion from ultrastable zeolite Y via a co‐templating route using alkali metal cations and nitrate anions but without organic structure directing agents. The mechanism, which involves zeolite framework – alkali metal cation – nitrate anion ordering, has been established by a combination of chemical and thermal analyses, Raman spectroscopy, computational modelling, and X‐ray powder diffraction. Ammonium exchange gives ZK‐5 with occluded ammonium nitrate and subsequent heating gives microporous zeolite ZK‐5. High silica forms of the zeolite ZK‐5 are prepared by an interzeolite conversion using inorganic cations and anions as templates. K+ and Cs+ cations and NO3− anions self‐assemble within its lta and pau cages with a high degree of space filling and exchange with NH4+ followed by heating gives a microporous solid. This approach offers an alternative and organic structure directing agent‐free route to directing zeolite synthesis.