Proton Conductance of a Superior Water-Stable Metal–Organic Framework and Its Composite Membrane with Poly(vinylidene fluoride)

Abstract

Proton-exchange membranes (PEMs) as separators have important technological applications in electrochemical devices, including fuel cells, electrochemical sensors, electrochemical reactors, and electrochromic displays. The composite membrane of a proton-conducting metal-organic framework (MOF) and an organic polymer combines the unique physical and chemical nature of the polymer and the high proton conductivity of the MOF, bringing together the best of both components to potentially fabricate high-performance PEMs. In this study, we have investigated the proton-transport nature of a zirconium(IV) MOF, MOF-808 (1). This superior-water-stability MOF shows striking proton conductivity with σ = 7.58 × 10 S·cm at 315 K and 99% relative humidity. The composite membranes of 1 and poly(vinylidene fluoride) (PVDF) have further been fabricated and are labeled as 1@PVDF-X, where X represents the mass percentage of 1 (as X%) in 1@PVDF-X and X = 10-55%. The composite membranes exhibit good mechanical features and durability for practical application and a considerable proton conductivity of 1.56 × 10 S·cm in deionized water at 338 K as well. Thus, the composite membranes show promising applications as alternative PEMs in diverse electrochemical devices.

Proton Conductivity of Composite Polyelectrolyte Membranes with Metal‐Organic Frameworks for Fuel Cell Applications

“…In a recent study, Tian and co‐workers reported on the preparation of composite membranes of poly(vinylidene fluoride) (PVDF) with Zr‐MOF‐808 showing high conductivities under high humidity conditions . As previously mentioned, this MOF possesses big internal pores and aperture diameters of 18 and 14 Å, respectively, and a high proton conductivity (7.6 × 10 −3 S cm −1 at 42 °C and 99% RH) .…”

“…A) Chemical structure of PVDF polymer. B) Plot of proton conductivity at different temperatures of PVDF@ZIF8 hollow nanostructures under anhydrous conditions …”

Recent Advances in Poly(vinylidene fluoride) and Its Copolymers for Lithium-Ion Battery Separators

“…The addition of a metal-organic framework to a polymer structure proved to increase the conductivity of the produced membrane without needing an electrolyte. The membrane also showed high durability and good mechanical properties [ 76 ].…”

A robust zirconium amino acid metal-organic framework for proton conduction

“…However, these MOFs suffer from either a lack of biocompatible character, the use of expensive or poorly environment-friendly chemicals and/or scale-up limitations. Series of Zr-carboxylate MOFs based on commercial (not bio-derived) linkers such as the Zr-terepthalate UiO-66 as well as the Zr-trimesate MOF-808 32 have also been studied as proton conductive materials, in particular the UiO-66’s series of functionalized solids that exhibit interesting performances being tuned by (i) the decoration of the pore wall with pendent acid groups (−CO 2 H, −SO 3 H) 4 , 33 – 36 or (ii) the incorporation of ligand defects saturated or not by acid treatment 37 – 39 . Some of these solids are however not exceeding the performances of Nafion.…”