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

Abstract

A novel metal‐organic framework, [Zn2(HCOO)(trz)3]n (1), has been successfully synthesized under solvothermal conditions. The central ZnII ions exhibit two different coordination environments: [ZnN3O] and [ZnN6], 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 (Ea) has investigated to deeply understand the proton conductivity mechanism.