Tuning proton conduction by different particle sizes in open-framework metal phosphates.

KVPC exhibit high proton conductive behaviours due to particles with different sizes. This is the first metal organic-phosphate framework in which proton conductivity has been tuned by different particle sizes. • KVPC exhibit different conductive behaviors due to particles with different sizes. • The conductivity of KVPC-S is high to 1.15 × 10−2 S cm−1 at 40 °C under 95% RH. • The conductivity of membranes reach up to 1.19 × 10-3 S cm−1 and remain no significant change within 6 h. The proton conductions of open-framework metal phosphates K 2 [(VO) 2 (HPO 4) 2 (C 2 O 4)] (KVPC) with large and small particle sizes, namely KVPC-L and KVPC-S, have been evaluated. Varied particle sizes result in different proton conductive behaviors. KVPC-S exhibits a high proton conductivity of 1.15 × 10−2 S cm−1 under 40 °C, 95% RH and possesses a stable proton conduction for 4 h. Furthermore, proton conductivities of composite membranes are investigated, and the value can reach up to 1.19 × 10-3 S cm−1 under 60 °C, 95% RH and remain no significant change within 6 h. [ABSTRACT FROM AUTHOR]