Cooperative structure-directing effects in the synthesis of a low-silica zeolite phillipsite analogue

A zeolite phillipsite (PHI) analogue with low silica contents has been synthesized from a NH4F–Al2O3–SiO2–piperazine–H2O system. The obtained zeolite PHI analogue grows as agglomerates of intergrown submicron-sized crystals. The synthesis process in fluoride-based media has been investigated. It has been unequivocally demonstrated that no zeolite phase occurred in the absence of piperazine or NH4F. The results of CHN elemental analyses as well as of TG analyses confirmed that both piperazine and NH4+ had been incorporated into the zeolitic structure. Thus, the zeolite PHI analogue is seemingly derived from the cooperative structure-directing effect of the organic molecule piperazine and the inorganic cation NH4+. The use of a suitable combination of inorganic cation and organic molecule in fluoride-based media may provide an effective means of exploring new frameworks with low Si/Al ratios.