Exploratory Synthesis of Low-Silica Nanozeolites through Geopolymer Chemistry

Nanozeolites are of great interest with the premise of their efficiency in traditional applications such as catalysis and separation, as well as their emerging applications including chemical sensors, medicine, and food industry. We report a new geopolymerization route for the synthesis of nanozeolites with different crystal structures by exploring the Na-Al-Si-H2O quaternary phase space under a mild hydrothermal condition. Nanostructured faujasite (FAU), cancrinite (CAN), and sodalite (SOD) zeolites with a crystallite size smaller than 40 nm were successfully produced from our exploration, as well as a submicron-sized Linde-Type A (LTA) zeolite. The transmission electron microscopy and nitrogen sorption analysis on representative zeolite samples showed that FAU and SOD zeolites exhibit textural mesopores, while CAN products have a more open aggregate structure. Our findings establish the geopolymerization as a convenient route for production of low-silica nanozeolites.