Remarkable Enhancement of Proton Conductivity by Introducing Imidazole into MOFs and Forming Composite Membranes

Abstract

A novel metal‐organic framework, [Zn 2 (HCOO)(trz) 3 ] n ( 1 ), has been successfully synthesized under solvothermal conditions. The central Zn II ions exhibit two different coordination environments: [ZnN 3 O] and [ZnN 6 ], in which the coordination N and O atoms are from Htrz and formic acid molecules. To effectively improve the proton conductivity of 1 , imidazole molecules are introduced into 1 to obtain 2HIm@ 1 (named as 2 ). Moreover, composite membranes of 2 ‐PVA‐X (X = 5, 10, 15, 20wt.‐%) are prepared. Alternating current (AC) impedance measurements reveal that 1 displays proton conductivity 7.95 × 10 –7 S cm –1 at 98 % RH and 323 K, while 2 shows high proton conductivity 1.51 × 10 –4 S cm –1 at 98 % RH and 318 K. It is worth noting that the proton conductivity of 2 increases about three orders of magnitude compared with that of 1 . Additionally, the measurements of proton conductivity on these membranes show that 2 ‐PVA‐10 has high proton conductivity 1.23 × 10 –4 S cm –1 at 98 % RH and 358 K. The activation energy ( E a ) has investigated to deeply understand the proton conductivity mechanism.