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

Abstract

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 expensive 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 preorganized 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 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 to 200 °C in the presence of 1 equiv. 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.