Toward the Synthesis of New Zeolite Structures in the Presence of Cesium: Zeolite MMU-1

Nanosized small-pore zeolites RHO and MMU-1 (a new Cs-Na modification of an EDI-type zeolite structure) were prepared in the presence of cesium hydroxide by changing the molar composition of the precursor zeolite solution. XRD, Raman, and FTIR results indicated that Cs had a structure-directing effect and controlled the formation of the respective zeolite phases. The presence of water played a crucial role, and when the amount of water was under a certain level, the zeolite cancrinite was formed. Solvent-free syntheses were attempted, and the results confirmed the conclusions drawn based on the water-mediated syntheses, namely that both Cs and water determine the nature of the product formed. The structure of the new zeolite MMU-1 was resolved by Rietveld refinement. MMU-1 was found to exhibit tetragonal symmetry, space group P42$_{1}$c (No. 114), and its framework is composed of four-membered and eight-membered TO$_{4}$-rings. The results reported suggest that there is the potential to synthesize other novel small-pore zeolite structures in the presence of cesium hydroxide by modifications of the chemical composition of the zeolite precursor solution.