Construction of Water-Stable Rare-Earth Organic Frameworks with Ambient High Proton Conductivity Based on Zirconium Sandwiched Heteropolytungstate.

Water-stable proton-conducting materials owning excellent performances at ambient temperatures are currently one of the crucial challenges. Herein, four water-stable three-dimensional polyoxometalate-based rare-earth organic frameworks have been successfully synthesized and formulated as H{Ln 4 (L) 2 (H 2 O) 21 [Zr 3 (OH) 3 (PW 9 O 34 ) 2 ]}·15H 2 O ( 1 - 3 ) (Ln = La ( 1 ), Ce ( 2 ), Pr ( 3 ); L = 3,5-pyridine dicarboxylic acid), which are the first examples of MOFs constructed by a zirconium sandwiched polyoxoanion. There are abundant coordinated water molecules functionalizing the Pr III centers, and simultaneously, plenty of lattice water molecules are fitted into the channel of the framework. A continuous H-bonding network is found between the architectures and plays an important role in stabilizing the structure. Benefiting from the consecutive H-bonding networks, compounds 1 - 3 showed high proton conductivities at ambient temperature (up to 1.05 × 10 -3 S·cm -1 under 98% RH) by a synergistic effect of the combined components.