Preparation and proton conductivity evaluation of a silicate gel composite doped with a metal–Schiff-base–POM-MOF

Abstract

A silica gel composite (denoted as 1–SG) doped with a proton-conductive metal–Schiff-base–POM-MOF, {[Cu3(L)2(H2O)4][Cu(DMF)4(SiW12O40)]·9H2O}n (1) (where L is N, N′-bis[1-(2-methoxyphenol-6-yl)-methylidene] hydrazine hydrate, DMF is dimethyl formamide, POM-MOF is polyoxometalates-based metal–organic framework), was prepared by sol–gel method. The structure of as-synthesized 1–SG was confirmed by infrared spectrometry and X-ray powder diffraction, and its proton conductivity was calculated based on electrochemical impedance spectroscopic measurement. It was found that the structural characteristics of complex 1 are retained successfully in the silica gel skeleton of as-prepared 1–SG. Besides, though 1–SG contains just 6.25 wt% complex 1, it exhibits good proton conductivities of as much as 1.51 × 10−3–1.26 × 10−2 S cm−1 in the temperature range of 25–100 °C under a relative humidity of 98 %; and in particular, it shows better proton conductivity than both complex 1 and silica gel at the same conditions, due to the presence of a large number of micropores and mesopores filled with “liquid”.