Experimental verification of double-four-ring-type aluminosilicate molecule as a single-source precursor for zeolite synthesis

Abstract

While a variety of functional zeolites have been synthesized using hydrothermal methods with conventional discrete Al and Si sources, control of the composition, structure, and function of the targeted zeolites often involves costly and time-consuming trial-and-error approaches. Despite ongoing efforts to manipulate zeolite formation by adjusting Al and Si sources and reaction conditions, limited attention has been given to studies on zeolite synthesis using molecular precursors (MPs) with pre-organized Al–O–Si bonds. Here, we demonstrate the synthesis of LTA-type zeolites using [TMA]4[Al4Si4O12(OH)8]·13H2O ([MP]; TMA = tetramethylammonium cation) with a double-four-ring (D4R)-type core structure, which is known to be a secondary building unit (SBU) in the LTA-type zeolite, as a MP. Here, we demonstrate the successful synthesis of LTA-type zeolites using [MP] under hydrothermal conditions at 100–200 °C in the presence of 1 equivalent of NaOH or NaCl. Notably, when discrete Al and Si sources were used instead of [MP] under otherwise identical conditions (the same Si/Al ratio, Na+ content, and temperature), GIS-, SOD-, and FAU-type zeolites lacking the D4R structure were obtained in addition to the LTA-type zeolites.