Influence of activated protons and acid–base pairs on proton conduction in imino-functionalized MOF-based hybrid membranes

The rich activated protons and effective proton-conducting paths are of importance to improve conductivities of conductors. Herein, a series of Brönsted acids as proton carrier and proton transfer sites is introduced into the highly stable MOF , contributing to create plentiful hydrogen bonds within frameworks. Consequently, the trifluoromethanesulfonic acid-embedded JUC-1000 ([Cu 24 (BDPO) 12 (H 2 O) 12 ]) displays the relatively highest conductivity of 7.04 × 10 −4 S cm −1 under ∼98% RH and 328 K, ∼16 times that of JUC-1000 (4.47 × 10 −5 S cm −1 ). When TMSA@JUC-1000 (TMSA = CF 3 SO 3 H) blended with chitosan (CS), the proton conductivity of TMSA@JUC-1000/CS-15 is the highest at ∼76% RH and 328 K (1.01×10 −2 S cm −1 ), which is six times higher than that of JUC-1000/CS (1.85×10 −3 S cm −1 ). The CS contains abundant –NH 2 and –OH groups as proton jumping sites, which would activate the –NH– or –OH bonds of JUC-1000 and the acidic groups in Brönsted acids . These would result in an increased content of activated protons and effective formation of H-bonding nets by acid-base interactions. The findings provide valuable insights into the potential application of MOFs materials in energy devices.