Pendent piperidinium-functionalized blend anion exchange membrane for fuel cell application

Alkaline anion exchange membrane fuel cell has fast cathode reactions and thus allows the use of low cost electrocatalysts. However, its practical application is hindered by the low hydroxide ion conductivity and alkaline stability of AEM. In this study, pendent piperidinium functionalized polyetheretherketone is synthesized and blended with polybenzimidazole for fabrication of composite anion exchange membrane. The pendent piperidinium functionalized side chains can create well-connected ionic transporting channels and thus impart the blend membranes high hydroxide conductivity (61.5–72.8 mS cm⁻¹ at 80 °C) and good tensile strength (42.8–58.9 MPa). Due to the strong interactions between polybenzimidazole and piperidinium groups of the polymers as confirmed by Fourier transform infrared spectroscopy, the piperidinium functionalized blend anion exchange membrane can retain 95% of its original OH⁻ conductivity value when treated in 1 M KOH at 60 °C for 576 h. The single fuel cell assembled with the membrane can yield a peak power density of 87 mW cm⁻² at 80 °C. Our work provides a new and effective method to balance the hydroxide conductivity and alkaline stability of anion exchange membranes.     

The effect of side chain length on the morphology and transport properties of fluorene-based anion exchange membranes

Poly[(fluorene alkylene)- co(biphenyl alkylene)] (PFBA) compounds with quaternary ammonium (QA) groups (PFBA-nC-QAs) that are linked with side chains of various lengths (n = 1～6 carbon atoms) are designed and synthesized by a superacid catalysis reaction, which has the advantages of low cost, easy synthesis and mild reaction conditions. The correlative properties of PFBA-nC-QAs, including water uptake, thermal stability, morphology, ion conductivity and alkaline stability, are discussed in detail. The side chain length is vital to the morphology and transport performance of PFBA-nC-QAs. As the side chain length increases, the alkaline stability and hydroxide ion conductivity of the prepared membranes improve with decreasing water uptake. Experimental results indicate that the hydroxide conductivity of PFBA-6C-QA is 154 mS cm^?1 at 80 °C. Moreover, no degradation of functional groups of PFBA-6C-QA is observed during 30 days of immersion in 2 M NaOH at 80 °C. The peak power density of PFBA-6C-QA is 278 mW cm^?2 at 60 °C with a hydrogen/air single fuel cell. By controlling the length of the polymer side chain, the method is simple and effective for building anion exchange membranes with high performance.     

Block poly(arylene ether nitrile ketone)s with comb-shaped alkyl chains as anion exchange membranes

A new approach is presented here for constructing higher-performance anion exchange membranes (AEMs) by combining block-type and comb-shaped architectures. A series of quaternization fluorene-containing block poly (arylene ether nitrile ketone)s (QFPENK-m-n) were synthesized by varying the length of hydrophobic segment as AEMs. The well-designed architecture, which involved grafting comb-shaped C10 long alkyl side chains onto the block-type main chains, formed efficient ion-transport channels, as confirmed by atomic force microscopy. As a result, the AEMs showed high hydroxide conductivities in the range of 34.3–102.1 mS⋅cm⁻¹ from 30 to 80 °C at moderate ion exchange capacities (IECs). Moreover, the hydrophobic segment with nitrile groups also exhibited a profound anti-swelling property for the AEMs, resulting in ultralow swelling ratios ranging from 4.7% to 7.1% at 30 °C and 7.5%–9.8% at 80 °C, as well as superb conductivity-to-swelling ratios at 80 °C. In addition, the AEMs displayed good mechanical properties, thermal and oxidative stability, and optimizable alkaline stability.     

Highly durable and conductive poly(arylene piperidine) with a long heterocyclic ammonium side-chain for hydroxide exchange membranes

Recently, the preparation of hydroxide exchange membranes (HEMs) without ether bonds have attracted much attention because of their high chemical stability. Hence, ether-bond free, highly durable, and conductive poly(arylene piperidine)s (PAPips) tethered with heterocyclic ammonium via hexyl spacer chains were prepared successfully for HEMs via a facile synthetic procedure. The effect of the cationic groups (quaternary ammonium, piperidinium, and morpholinium) on the properties of the corresponding PAPip-based HEMs, including the morphology, hydroxide conductivity, and alkaline and chemical stability were systematically investigated. The as-designed PAPip-based membranes exhibited excellent overall performance. The membranes attached with piperidinium (IEC = 1.64 mmol g⁻¹) exhibited a hydroxide conductivity of 0.082 S cm⁻¹ at 80 °C and exhibited significant alkaline stability which maintained 80.1% of its conductivity after immersion in 1 M NaOH at 80 °C for 1500 h. The as-prepared membrane also presented a peak power density of 76 mW cm⁻² at 80 °C in a H₂/O₂ HEMFC. The resulting HEMs also showed excellent mechanical properties, thermal stability, and well-defined phase separation.     

Enhanced ionic conductivity of anion exchange membranes by grafting flexible ionic strings on multiblock copolymers

A new strategy to prepare high-conductivity anion exchange membranes (AEMs) is presented here. A series of phenolphthalein-based poly(arylene ether sulfone nitrile) multiblock AEMs has been synthesized by selectively grafting flexible ionic strings on hydrophilic segments to form ionic regions. Moreover, the phenolphthalein groups are introduced to force chains apart and create additional interchain spacing. In addition, the nitrile groups suspended on main chains are aimed at enhancing the anti-swelling behavior of as-prepared AEMs. Along these processes, well-defined phase separation has been attained, forming excellent ion-transport channels. The effective phase separation has been confirmed by atomic force microscopy. Finally, as-prepared AEMs exhibit a high hydroxide conductivity, ranging from 40.1 to 121.6 mS cm⁻¹ in the temperature range of 30–80 °C, and superior ionic conductivity to IEC ratio at 80 °C. Furthermore, excellent thermal stability and desirable mechanical strength have been rendered by as-prepared AEMs. However, the alkaline stability of as-prepared AEMs requires further optimization.     

Crosslinked poly(arylene ether sulfone) block copolymers containing pendant imidazolium groups as both crosslinkage sites and hydroxide conductors for highly selective and stable membranes

Crosslinked poly(arylene ether sulfone)s with pendant imidazolium units, both as crosslinkage sites and hydroxide conductors, were developed as anion exchange membranes (AEMs). These crosslinked membranes, with IECs of 0.80–1.21 meq/g, showed high hydroxide conductivity over 0.01 S/cm at 20 °C and 0.06 S/cm at 80 °C. Furthermore, the crosslinked membranes containing imidazolium groups on the side chains of the polymer exhibited good thermal, mechanical and dimensional stability, as well as excellent chemical stability at high pH. The combination of high hydroxide conductivity and low methanol permeability caused these crosslinked membranes to have very high selectivity up to 13 × 10⁵ S s/cm³, suggesting our crosslinked membranes are suitable for DMAFCs. These membranes can also be used for various other applications including gas separations.     

Comb-shaped fluorene-based poly(arylene ether sulfone nitrile) as anion exchange membrane

A series of comb-shaped fluorene-based poly (arylene ether sulfone nitrile) (CFPESN–x) was synthesized as anion exchange membranes (AEMs). The well-designed architecture of fluorene-based main chains and comb-shaped C8 long alkyl side chains containing quaternary ammonium groups was responsible for the clear microphase-separated morphologies, as confirmed by small angle X-ray scattering and atomic force microscopy. Moreover, nitrile groups on main chains also showed a profound influence on membrane morphology and properties. CFPESN–x exhibited more interconnected ionic domains with increasing the nitrile group content resulting in higher conductivities and anti-swelling property. Then CFPESN–x exhibited high ionic conductivities in the range of 27.1–91.5 mS cm⁻¹ from 30 to 80 °C and superior ratios of conductivity to swelling ratio at 80 °C at moderate IECs. Moreover, CFPESN–x also showed good mechanical properties and thermal stability, and optimizable alkaline stability and single cell performance.     

High alkaline stability and long-term durability of imidazole functionalized poly(ether ether ketone) by incorporating graphene oxide/metal-organic framework complex

The poly(ether ether ketone) (PEEK) was prepared as organic matrix. ZIF-8 and GO/ZIF-8 were used as fillers. A series of novel new anion exchange membranes (AEMs) were fabricated with imidazole functionalized PEEK and GO/ZIF-8. The structure of ZIF-8, GO/ZIF-8 and polymers are verified by ¹H NMR, FT-IR and SEM. This series of hybrid membranes showed good thermal stability, mechanical properties and alkaline stability. The ionic conductivities of hybrid membranes are in the range of 39.38 mS cm^?1–43.64 mS cm^?1 at 30 °C, 100% RH and 59.21 mS cm^?1–86.87 mS cm^?1 at 80 °C, 100% RH, respectively. Im-PEEK/GO/ZIF-8-1% which means the mass percent of GO/ZIF-8 compound in Im-PEEK polymers is 1%, showed the higher ionic conductivity of 86.87 mS cm^?1 at 80 °C and tensile strength (38.21 MPa) than that of pure membrane (59.21 mS cm^?1 at 80 °C and 19.47 MPa). After alkaline treatment (in 2 M NaOH solution at 60 °C for 400 h), the ionic conductivity of Im-PEEK/GO/ZIF-8-1% could also maintain 92.01% of the original ionic conductivity. The results show that hybrid membranes possess the ability to coordinate trade-off effect between ionic conductivity and alkaline stability of anion exchange membranes. The excellent performances make this series of hybrid membranes become good candidate for application as AEMs in fuel cells.     

Dense 1,2,4,5-tetramethylimidazolium-functionlized anion exchange membranes based on poly(aryl ether sulfone)s with high alkaline stability for water electrolysis

Anion exchange membranes with enough alkaline stability and ionic conductivity are essential for water electrolysis. In this work, a class of anion exchange membranes (PAES-TMI-x) with dense 1,2,4,5-tetramethylimidazolium side chains based on poly(aryl ether sulfone)s are prepared by aromatic nucleophilic polycondensation, radical substitution and Menshutkin reaction. Their chemical structure and hydrophilic/hydrophobic phase morphology are characterized by hydrogen nuclear magnetic resonance (¹H NMR) and atomic force microscope (AFM), respectively. The water uptake, swelling ratio and ionic conductivity for PAES-TMI-x are in the range of 23.8%–48.3%, 8.3%–14.3% and 18.22–96.31 mS/cm, respectively. These AEMs exhibit high alkaline stability, and the ionic conductivity for PAES-TMI-0.25 remains 86.8% after soaking in 2 M NaOH solution at 80 °C for 480 h. The current density of 1205 mA/cm² is obtained for the water electrolyzer equipped with PAES-TMI-0.25 in 2 M NaOH solution at 2.0 V and 80 °C, and the electrolyzer also has good operation stability at current density of 500 mA/cm². This work is expected to provide a valuable reference for the selection and design of cations in high-performance AEMs for water electrolysis.     

Synthesizing spindle-shaped anion exchange membranes to improve conductivity and stability

High ionic conductivity and excellent alkaline stability are very important for solid electrolyte. Therefore, spindle-shaped anion exchange membranes (AEMs) based on poly (arylene ether ketone) and 1-Bromo-N,N,N-trimethylhexane-6-aminium bromide (Br-QA) have been prepared. The obtained Br-QA can be grafted with poly (arylene ether ketone) main chains to form micro-phase separation structure enhancing the ionic conductivity. Especially, the grafting quaternary ammonium (QA) cation groups are separated by alkyl bromine endows the AEMs with alkaline stability features. Simultaneously, the OH⁻ conductivity of the QA-PAEK-0.6 obtained membranes is 0.046 S/cm under fully hydrated conditions at 60 °C. After immersing into 1 M NaOH alkaline solution for 15 days at 60 °C, the anionic conductivity still high to 0.03 S/cm. Meanwhile, the poly (arylene ether ketone) backbones provide excellent mechanical properties and the Br-QA cation groups also possess good thermal stability, which satisfy the requirement of wide applications.     

Comparison of alkaline fuel cell membranes of random & block poly(arylene ether sulfone) copolymers containing tetra quaternary ammonium hydroxides

A series of modified anion conductive block poly(arylene ether sulfone) copolymer membranes containing a selective substituted unit, 15%, 20% and 25% 4,4′-(2,2-diphenylethenylidene) diphenol, were prepared for use in alkaline fuel cells. The anion exchange membranes were synthesized by first introducing chloromethyl groups. Quaternary ammonium groups could then be added to the tetra-phenyl ethylene units, followed by subsequent ion exchange. The tetra quaternary ammonium hydroxide polymers showed high molecular weights and exhibited high solubility in polar aprotic solvents. The block copolymer membrane showed higher ionic conductivity (21.37 mS cm⁻¹) than the random polymer membrane of similar composition (17.91 mS cm⁻¹). The membranes showed good chemical stability in 1.0 M KOH solution at 60 °C. They were characterized by ¹H NMR, FT-IR, TGA and measurements of ion exchange capacity, water uptake and ionic conductivity.     

Anion exchange membranes based on poly (ether ether ketone) containing N-spirocyclic quaternary ammonium cations in phenyl side chain

It was reported that the existence of N-spirocyclic quaternary ammonium (QA) cation could improve alkaline stability of anion exchange membrane materials (AEM). Therefore, the cyclo-quaternization reaction with pyrrolidine (Pyr) and piperidine (Pip) was carried out to prepare quaternized poly (ether ether ketone)s bearing five-membered and six-membered N-spirocyclic quaternary ammonium (QA) groups in the phenyl side chains (QPEEK-spiro-pyr and QPEEK-spiro-pip), respectively. From the transmission electron microscope, the hydrophilic-hydrophobic phase-separated morphology was formed in QPEEK-spiro membranes after incorporating N-spirocyclic QA cations and bulky spacer simultaneously in the phenyl side chain. The effect of N-spirocyclic QA groups on performance of resulted AEMs was then studied in detail. The anion conductivities of QPEEK-spiro-pyr and QPEEK-spiro-pip in OH^? form at 80 °C were 49.6 and 30.9 S cm^?1, respectively. The remaining proportions of hydroxide conductivity for QPEEK-spiro-pyr and QPEEK-spiro-pip membranes after immersing in 1 M NaOH at 60 °C were 81.0% and 74.7%, respectively, which were higher than that of 62.3% for QPEEK-TMA containing conventional QA groups in the phenyl side chain. Fuel cell assembled with QPEEK-spiro-pyr achieves a peak power density of 90 mW cm^?2. These results indicate the strategy of simultaneously introducing N-spirocyclic QA cations and bulky spacers can improve the performance of AEM to a certain extent. There are some other factors that influence the alkaline stability of the prepared AEMs, such as the existence of ether bonds in the main chain. However, this work still provides a valuable reference towards the molecular design of AEMs with improved performance.     

Block copolymer anion exchange membrane containing polymer of intrinsic microporosity for fuel cell application

High hydroxide conductivity and good stability of anion exchange membranes (AEMs) is the guarantee that anion exchange membrane fuel cells (AEMFCs) yield high power output for a long time. Balanced conductivity and stability can be better guaranteed by adopting a relatively low ion exchange capacity (IEC) while reducing the ion transport resistance Herein, a novel block copolymer AEM was designed and synthesized, which contains hydrophobic polymer of intrinsic microporosity (PIM) blocks and hydrophilic, quaternized polysulfone (PSF) blocks. The PIM block imparts high free volume to the membrane so that the resistance of hydroxide ion transport can be reduced; meanwhile, the hydrophilic block can self-assemble more easily to produce a better developed hydrophilic microphase, which may function as efficient channels for hydroxide ion transport. Both transmission electron microscopy images and small-angle X-ray scattering patterns suggested that the resulting AEM possessed a microphase separated morphology. The membrane showed a conductivity of 52.6 mS cm^-l at 80 °C with a relatively low IEC of 0.91 mmol g^?1. It also exhibited a good dimensional stability, swelling ratio maintained almost constant (ca. 17%) at 25 to 80 °C. The assembled H₂/O₂ fuel cell yielded a peak power density of 270 mW cm^?2 at 560 mA cm^?2. Our work demonstrates that incorporation of PIM in an AEM by means of block polymerization is an efficient way of promoting microphase separation and facilitating ion transport.     

Preparation and characterization of a polyvinyl alcohol grafted bis-crown ether anion exchange membrane with high conductivity and strong alkali stability

A new type of symmetrical bis-crown ether is prepared by connecting dibenzo-18-crown-6 ether on both sides of the chromotropic acid, and then grafting the aforementioned bis-crown ether onto polyvinyl alcohol matrix to prepare a series of anion exchange membranes (AEMs), which their have high conductivity and strong alkali stability. These synthesized membranes were named B-C_X%-P AEMs (x is the mass percentage of the symmetrical bis-crown ether (B–C)). Then, the chemical structure of aforementioned AEMs were verified by means of ¹H NMR, FT-IR and UV. Meanwhile, the OH⁻ conductivity, alkaline stability and single cell performance of the synthesized membrane were also investigated. The results revealed that the conductivity of B–C_30%-P membrane is the highest at 80 °C (235 mS cm⁻¹), and the power density is also the highest (197 mW cm⁻²), and the alkali stability of the membrane synthesized in this paper was also improved. The conductivity at 80 °C was only reduced by 4%, which was obtained by immersing the B–C_30%-P membrane immersed in 6 mol L⁻¹ KOH solution for 168 h, which the aforementioned results proved that the synthesized membrane in this research had excellent OH⁻ conductivity and alkaline stability.     

Constructing micro-phase separation structure by multi-arm side chains to improve the property of anion exchange membrane

In order to improve the performance of anion exchange membrane (AEMs) as the core component of alkaline fuel cell, a novel pentamethyl-contained phenolphthalein multi-arm monomer is synthesized. The highly imidazolium-functionalized poly (arylene ether ketone) membrane (Im-PEK-x) are prepared by introducing 1,2-dimethylimidazole as hydrophilic segments. The monomer, polymer and anion exchange membranes are confirmed by ¹H NMR spectra. The well-defined micro-phase separated structure of membranes is conducive to ion transport and the structure is investigated by TEM and SAXS. The imidazolium-functionalized membranes (Im-PEK-0.8) exhibits high ionic conductivity (0.148 S/cm at 80 °C). The tensile strength of Im-PEK-0.8 membrane is 30.06 MPa. Furthermore, after immersing in 60 °C, 2 M NaOH solution for 240 h, the ionic conductivity remains 0.092 S/cm for Im-PEK-0.8. The 1,2-dimethylimidazole enhance alkaline stability by steric effect of the substituent group at the C2 position. All these results indicate that this is a new method to enhance conductivity and stability performance of AEMs.     

Macromolecule sulfonated Poly(ether ether ketone) crosslinked poly(4,4′-diphenylether-5,5′-bibenzimidazole) proton exchange membranes: Broaden the temperature application range and enhanced mechanical properties

Proton exchange membranes with a wide application temperature range were fabricated to start high-temperature fuel cells under room temperature. The volume swelling stability, oxidative stability as well as mechanical properties of crosslinked membranes have been improved for covalently crosslinking poly(4,4′-diphenylether-5,5′-bibenzimidazole) (OPBI) with fluorine-terminated sulfonated poly(ether ether ketone) (F-SPEEK) via N-substitution reactions. High proton conductivity was simultaneously realized at both high (80–160 °C) and low (40–80 °C) temperatures by crosslinking and jointly constructing hydrophilic-hydrophobic channels. The crosslinked membranes exhibited the highest proton conductivity of 191 mS cm⁻¹ at 80 °C under 98% relative humidity (RH) and 38 mS cm⁻¹ at 160 °C under anhydrous, respectively. Compared with OPBI membrane, the fuel cell performance of the crosslinked membranes showed higher peak power density at full temperature range (40–160 °C).     

Novel poly(carbazole-butanedione) anion exchange membranes constructed by obvious microphase separation for fuel cells

To develop anion exchange membranes with excellent chemical stability and high performance. A series of quaternary ammonium functionalized (hydrophilic) hydrophobic rigid poly (carbazole-butanedione) (HOCB-TMA-x) anion exchange membranes were prepared, where x represents the percentage content of hydrophobic unit octylcarbazole (OCB). Due to the introduction of hydrophobic rigid unit octylcarbazole and hexyl flexible side chain, the hydrophilic-hydrophobic microstructure of AEMs was developed. The AEMs exhibit excellent overall performance, specifically the low swelling ratio HOCB-TMA-30 membrane exhibits the highest OH^? conductivity of 152.9 mS/cm at 80 °C. Furthermore, the ionic conductivity of AEM decreased by only 9.5% after 2250 h of immersion in 1 M NaOH. The maximum peak power density of a single cell with a current density of 4.38 A/cm² at 80 °C was 1.85 W/cm².     

Novel self-cross-linked multi-imidazolium cations long flexible side chains triblock copolymer anion exchange membrane based on ROMP-type polybenzonorbornadiene

A novel benzonorbornadiene derivative (BenzoNBD-Bis(Im⁺Br⁻-Im⁺I⁻)) grafted by multi-imidazolium cations side-chains combined the rigid alkyl spacer and flexible alkoxy spacer is designed and synthesized. Then, the BenzoNBD-Bis(Im⁺Br⁻-Im⁺I⁻) monomer is copolymerized with the epoxy functionalized norbornene monomer (NB-MGE) and norbornene (NB) via ring-opening metathesis polymerization (ROMP) using Grubbs 3rd catalyst. All as-designed triblock copolymer membranes (TBCMs) show a thermal decomposition temperature beyond 310 °C and can well be dissolved in common organic solvents. The self-cross-linked structure of anion exchange membrane (AEM) is confirmed by gel fraction and tensile measurement. The water uptake and swelling ratio of TBCMs and AEMs are also measured. Major properties required for AEMs such as ion exchange capacity (IEC), hydroxide conductivity and alkaline stability are investigated. AEM-9.09 shows a hydroxide conductivity of 100.74 mS cm⁻¹ at 80 °C. Besides, the micro-phase separated morphology of AEM is confirmed by TEM, AFM and SAXS analyses, AEMs formed distinct micro-phase separation. The as-prepared AEM exhibits a peak power density of 174.5 mW cm⁻² at 365.1 mA cm⁻² tested in a H₂/O₂ single-cell anion exchange membrane fuel cell (AEMFC) at 60 °C. The newly developed strategy of self-cross-linked multi-imidazolium cations long side-chains triblock benzonorbornadiene copolymer provides an effective method to develop high-performance AEMs.     

Anion exchange composite membrane based on ionic liquid-grafted covalent organic framework for fuel cells

Covalent organic frameworks (COFs) have been considered promising hydroxide-conducting materials for their highly ordered crystalline porous structure and tunable functionality. However, the lack of hydroxyl conduction functional groups on the COFs frameworks restricts their further development in anion exchange membrane fuel cells (AEMFCs). At present, impregnated ionic liquids (ILs) are mainly used to solve this problem, but they still face the challenge of ILs leakage under working conditions. Here, we report a novel IL-functionalized covalent organic framework (IL-COF), which is prepared by grafting guanidinium-based IL onto the channel walls of COF via the Williamson ether reaction and then doped into guanidinium-functionalized poly(2,6-dimethyl-1,4-phenylene oxide) (GPPO) to prepare IL-COF/GPPO composite membranes. The ILs grafted into the COFs nanochannels act as the “active sites” in the membranes to enhance the migration rate of the hydroxide ions and thus improve the conductivity. Accordingly, the hydroxide conductivity of the resultant IL-COF/GPPO composite membrane with IL-COF doping amount of 5 wt% can reach up to 89.93 mS cm^?1 at 80 °C under hydrated condition, 61% higher than that of the pristine GPPO membrane. Meanwhile, its hydroxide conductivity retains 90.31% after alkaline treatment for 14 days. Compared with IL-impregnated COF composite membrane (IL@COF/GPPO), IL-COF/GPPO membrane has superior hydroxyl conductivity and long-term stability since chemical grafting can more firmly immobilize ILs into COF channels than impregnation.     

Enhanced proton conductivity of poly (arylene ether ketone sulfone) containing uneven sulfonic acid side chains by incorporating imidazole functionalized metal-organic framework

In this study, the side-chain type hybrid proton exchange membranes which based on metal-organic frameworks (MOFs) and organic matrix of sulfonated poly (arylene ether ketone sulfone) containing both long and short sulfonic acid side chains (S-C-SPAEKS) were prepared. MOF-801 was used as a template and then imidazole was encapsulated into MOF-801 as additional proton carriers. In imidazole -MOF-801, imidazole was used as a functional group to coordinate with the zirconium metal site of the functional group. Imidazole-MOF-801 and hybrid membranes were characterized by XRD, ¹H NMR and FT-IR. These hybrid membranes exhibited excellent proton conductivities and good thermal stabilities. Compared to pure S-C-SPAEKS (0.0487 S cm^?1 at 30 °C, 0.0809 S cm^?1 at 80 °C), S-C-SPAEKS/0.5% Im-MOF-801 showed a great improvement (0.1205 S cm^?1 at 30 °C, 0.1992 S cm^?1 at 80 °C), which was about 2.5 times higher than that of pure S-C-SPAEKS and 2 times higher than that of commercial Nafion117 (0.1003 S cm^?1 at 80 °C). The results indicated that imidazole functionalized MOFs and uneven side chain structure synergistically made an important contribution to proton transport. This series of hybrid membranes have the potential to be used as alternative proton exchange membranes.