Syntheses And Properties Of Proton Conducting Inorganic Microporous Materials

Aluminophosphate(Al PO) molecular sieves and related open-framework structures as the main family of inorganic microporous materials have aroused widespread interest due to their diverse structures and important applications in absorption, catalysis and separation. The synthesis of Al PO zeolitic compounds typically involves the use of organic templates or structure-directing agents. However, the employment of organic SDAs, usually expensive and toxic, brings some drawbacks for the practical applications of these materials, such as high synthetic cost, environmental pollution caused by the reaction wastes, and high energy consumption upon calcination for the removal of organic SDAs, etc.The searching for new applications of zeolite materials is of continuing interest. Proton conductivity is important for the performance of solid electrolytes in fuel cells. Zeolitic materials with well-defined pore architectures and variable framework compositions are potential candidates for electrochemical applications as proton-transport materials and solid electrolytes. However, compared to the extensively studied metal organic frameworks(MOFs) and coordination polymers(CPs), the investigation of zeolitic materials in proton conducting applications is limited. So far, only several typical zeolites, such as HZSM-5, HBeta, FAU have been reported to possess proton conduction property.The presence of water molecules and extensive H-bond networks is a vital factor for the proton conductors. In the organotemplate-free zeolitic compounds, more water molecules may be occluded in the pores instead of organic SDAs to stabilise the whole structure. On the other hand, the alkali metal ions(e.g. Na+) in the pores of zeolitic materials may affect the proton transfer. Thus, the organotemplate-free synthesis of zeolites in alkali metal-containing system will provide more opportunities for the discovery of new zeolitic proton conducting materials.In this work, we choose sodium salts as alkali resource and try to synthesize aluminophosphate and aluminosilicate molecular sieves without organic template under hydrothermal condition. The proton conducting conductivity of the as-synthesized compounds have been studied, and the influence of water moleculars and alkali cations in the molecular sieves on the proton conductivities has been investigated. The main results are as follows:A new open-framework aluminophosphate Na6[(Al PO4)8(OH)6]·8H2O(JU103) has been synthesized by utilization of the organotemplate-free synthetic route in Al2O3–P2O5–Na2O–H2O system under hydrothermal condition. The as-prepared JU103 possesses two-dimensional intersecting 8-ring channels. Single-crystal diffraction analysis indicates that JU103 contains large amount of H2 O and sodium cations. JU103 exhibits proton conduction property due to the high content of water molecules in the pores. The proton conductivity of the as-synthesized JU103 is 3.59×10-3 S cm-1 at 98% relative humidity(293 K), and will be increased to 9.45×10-3 S cm-1 at 333 K in water.FAU-type zeolites with different Si/Al ratios have been synthesized in Al2O3–Si O2–Na2O–H2O system under hydrothermal condition. Elements analysis indicates that large amount of sodium cations are located in the channels of the zeolites. The proton conductivity of the as-synthesized Na Y is 4.87×10-3 S cm-1 at 98% relative humidity(293 K), a bit higher than that of Na X(3.99×10-3 S cm-1 at 98% relative humidity, 293 K). The proton conductivity of Na Y is increased to 2.24 ×10-2 S cm-1 at 353 K in water.