Steam-Assisted Synthesis of an Extra-Stable Polyoxometalate-Encapsulating Metal Azolate Framework: Applications in Reagent Purification and Proton Conduction

Different from the conventional synthesis approaches, such as hydrothermal or solvothermal synthesis, a porous metal azolate framework encapsulating Keggin-type [SiW12O40](4-) anions was prepared by an environmentally friendly, low-cost, and highly efficient steam-assisted conversion method for the first time. The nanosized polyoxometalates as a template were encapsulated by a zeotype 6(4)4(8) cage constructed by 28 nuclear zinc atoms connected through 32 Trz ligands. The obtained composite exhibits excellent thermal and chemical stability; meanwhile, its special ability to selectively absorb water from alcohols makes it efficiently separate water from analytically pure ethanol, with the result that water content decreases from 0.23 to 0.05wt%, which is superior to the standard of chromatographic grade ethanol (<0.1wt%). Besides, alternating current (ac) impedance experiments also reveal that the hybrid is a kind of proton conductive material.