Three orders of magnitude enhancement of proton conductivity of porous coordination polymers by incorporating ion-pairs into a framework

Abstract

A clathrate NH₄Br@HKUST-1 has been prepared by means of soaking the metal–organic-framework, HKUST-1, in ammonium bromide saturated ethanol solution at ambient temperature. Both NH₄Br@HKUST-1 and HKUST-1 show the same framework structure. The formula of the clathrate is approximately expressed as Cu₃(BTC)₂(NH₄Br)_1.15. The thermal stability of the metal–organic framework is not affected by incorporating ammonium bromide into its pores. The impedance spectra measurements were performed for both NH₄Br@HKUST-1 and HKUST-1 in anhydrous and selected relative humidity environments, disclosing that the conductivity of NH₄Br@HKUST-1 is enhanced by three/four orders of magnitude under the same conditions with respect to HKUST-1. This study provided an efficient strategy to achieve new high conductivity proton transport materials.