Synthesis of Template-Free Zeolite Nanocrystals by Reverse Microemulsion−Microwave Method

Many new applications for zeolite materials such as low dielectric constant films for chips and polymer−zeolite nanocomposite membranes for fuel cells require small, uniform, dispersible, and template-free zeolite nanocrystals, whose synthesis has so far proved difficult. Here we report an effective strategy to produce such zeolite nanocrystals by using microwave heating in reverse microemulsion (water in oil). The reverse microemulsion possibly acts as a space-confining nanoreactor, and microwave provides fast, homogeneous, and preferential heating of the aqueous phase (not the oil phase) where zeolite crystals are produced. As an example, the synthesis of template-free zeolite A nanocrystals (40−80 nm) is presented. The method demonstrated can potentially provide a general route to synthesize small, uniform, dispersible, and template-free zeolite nanocrystals.