Probing the ionic transport dynamics in ionic liquid incorporated CuBTC-Metal-Organic Framework based PVdF-HFP nanocomposite membranes

摘要

CuBTC-Metal-Organic Framework (MOF) has been prepared by solvothermal synthesis method and ionic liquid (IL) 1-butyl-3 methylimidazolium tetrafluomborate (BMIMBF4) has been incorporated at different wt% into the CuBTC-MOF. The composite nanofiller has been dispersed in poly (vinylidene fluoride-co-hexafluompropylene) (PVdF-HFP) polymer electrolyte system. Shifting of FTIR vibrational modes of carboxylate group is due to metalligand bond elongation upon interaction of ions of IL with CuBTC-MOF. The binding energy of Cu spin-orbit peak increases with incorporation of IL as obtained from XPS spectra suggesting motion of BET anions of IL towards the Cu metal nodes of MOF. Periodic oscillation and coordination structure of Cu K-edge are observed in k-space and R-space scanning EXAFS data. Non-Debye dielectric relaxation dynamics is observed from dielectric permittivity and modulus spectra with ionic conductivity of 8.7 x 10(-3) Scm(-1) at 50 wt% of IL incorporation in the composite polymer electrolyte at 380 K. The electrochemical stability profile increases with increasing IL concentration and attains 6.1 V at 50 wt% of IL.