High Proton Conductivity of a Cadmium Metal–Organic Framework Constructed from Pyrazolecarboxylate and Its Hybrid Membrane

Abstract

A new type of metal−organic framework, [Cd 2 (pdc)(H 2 O)(DMA) 2 ] n (pdc = 3,5-pyrazoledicarboxylic acid; DMA = dimethylamine), named Cd-MOF, was synthesized and characterized. There are regular rectangular pore channels containing a large number of dimethylamine cations in the crystal structure. AC impedance test results show the proton conductivity of Cd-MOF reaches 1.15 × 10 −3 S cm −1 at 363 K and 98% RH. In order for its application in fuel cells, the Cd-MOF was introduced into a sulfonated polyphenylene oxide matrix to prepare a hybrid membrane, and the proton conductivity of the hybrid membrane has a high value of 2.64 × 10 −1 S cm −1 at 343 K and 98% RH, which is higher than those of most MOF polymer hybrid membranes. The proton conductivity of the hybrid membrane of the SPPO polymer still maintains a certain degree of stability in a wide temperature range. To the best of our knowledge, it is the first proton exchange membrane that combines pyrazolecarboxylate cadmium MOFs and an SPPO polymer with high proton conductivity and good stability. This research may help to further develop the application of MOFs in the field of proton exchange membrane fuel cells.

A multifunctional anionic metal–organic framework for high proton conductivity and photoreduction of CO2 induced by cation exchange

“…Previously reported achievements based on various MOFs are presented in Table S4, † where the proton conductivity of NH 4 + @In-MOF24 is used for comparing with these listed experimental results. Clearly, the performances of NH 4 + @In-MOF24 locate at a middle level, compared to these covered proton conductive MOFs, such as CDs@MOF-802 possessing a value of 1.13 × 10 −1 S cm −1 under 25 °C and 98% RH, 26 Im@MOF-808 with a value of 3.45 × 10 −2 S cm −1 at 60 °C and 99% RH, 27 MOF-801 with a value of 1.88 × 10 −3 S cm −1 at 25 °C and 98% RH 28 and Cd-MOF with a value of 1.15 × 10 −3 S cm −1 at 90 °C and 98% RH, 29 and so on.…”

Enhancing Proton Conductivity of Nafion Membrane by Incorporating Porous Tb-Metal–Organic Framework Modified with Nitro Groups

“…A similar phenomenon was also discovered in membranes 7 and 8 . It was considered that −NH 2 groups or NH 3 guests were more conducive to improving proton behaviors of composite membranes because strong hydrogen bonds can be formed between basic −NH 2 or NH 3 and acidic −SO 3 H groups of Nafion, which can enhance the compatibility of Nafion and MOFs and form consecutive proton transfer pathways. ,,,, Results of our previous works show that −COOH groups anchored on the surface of MOFs also can improve σ H+ values of composite membranes (membranes 9 – 12 ), because of their acidity and hydrophilicity. The improvement ratio of MOFs modified with acidic −COOH groups was lower than that of MOFs modified with basic −NH 2 groups, which may be explained because the interactions between −COOH and −SO 3 H groups were relatively weaker and the compatibility of MOFs and Nafion was lower.…”

“…So, the proton conductivity (σ H+ ) of the PEM is an important factor for PEMFC efficiency. PEM candidate materials should possess high proton conductivity and good chemical and thermal stability under fuel cell operating conditions. − It is well-known that the Nafion series of proton exchange membranes exhibit high σ H+ (10 –1 to 10 –2 S·cm –1 ) at 60–80 °C and 98% relative humidity (RH), and they are widely used in practical fuel cell devices . However, the structure of the Nafion membrane could be damaged and its σ H+ would be largely decreased at high temperature.…”

“…7−9 It is well-known that the Nafion series of proton exchange membranes exhibit high σ H+ (10 −1 to 10 −2 S•cm −1 ) at 60−80 °C and 98% relative humidity (RH), 10 and they are widely used in practical fuel cell devices. 11 However, the structure of the Nafion membrane could be damaged and its σ H+ would be largely decreased at high temperature. The low thermal stability of Nafion limits its large-scale realistic application.…”

Space-Confined Nucleation of Semimetal-Oxo Clusters within a [H7P8W48O184]33– Macrocycle: Synthesis, Structure, and Enhanced Proton Conductivity

“…Last but not least, the through tunnels (8.36 Å × 10.11 Å) stacked by the aforementioned 2D layers along the c axis is filled with a host of free watery molecules, which afford primary highways for the straightforward proton migration. Moreover, hydrophilic sites such as DMA cations in the lattice would further facilitate the protonation of the water molecules to generate hydrated protons. , Aided by the nested H 3 O + as plausible molten carriers, the combined protons could diffuse at a high speed within the conduits (Figures d and S13). , …”