Improving the proton conductivity of MOF materials by regulating the pore space

Abstract

The construction of metal-organic frameworks (MOFs) with structural tunability, designability, and high stability is crucial in proton conduction studies. In this paper, MOF-801 and UiO-66 were used as precursors. A solvothermal synthesis method was employed to modulate the pore space of composite MOFs. The hydrogen-bonding network and structure within the pore cavities are adjusted by varying the molar ratios of fumaric acid and terephthalic acid to improve the proton transfer rate and proton conductivity of the materials. A total of 14 materials, MOF/MOG-801&UiO-66-X (X is the molar ratio of fumaric acid and terephthalic acid) were synthesised, the variation of proton conductivity with temperature of which was investigated at different tempertures and humidities. The results shows that MOG-801&UiO-66–1:1 has the best proton conductivity with 0.12 S cm−1 at 353 K and 100 % RH, which is 5 times higher than that of MOF-801&UiO-66–1:3 (2.54 × 10−2 S cm−1), 11 times higher than that of MOF-801 and 22 times higher than that of UiO-66. Based on the calculated activation energy and structural characterisation, the proton conduction mechanism of the composite was investigated. This work opens up novel research fields for the design of new proton-conducting MOF materials.