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

Abstract

A rigid carboxylate ligand with a nitro functional group was selected to coordinate with Tb(III) cation, and Tb-MOF ({[Tb 4 (L) 4 (OH) 4 (H 2 O) 3 ]•8H 2 O} n , H 2 L = 2-nitroterephthalic acid) with large porous and excellent hydrophilicity was obtained successfully. The obtained Tb-MOF was filled into the Nafion matrix to improve its proton conduction performance. The Tb-MOF/ Nafion composite membrane was characterized by PXRD, IR, and thermogravimetry (TG) and for water uptake, area swelling, and proton conductivity. The activity energy, E a , value of the composite membrane, which is a very important factor affecting the proton conduction performance of the membrane, was fitted and calculated. It was revealed that Tb-MOF can improve the proton conductivities of composite membranes, and the improvement degree and E a value were both affected by Tb-MOF content. When Tb-MOF content was 5%, the proton conductivity of the composite membrane was 1.53 × 10 −2 S•cm −1 at 100% RH and 80 °C, which is 1.81 times that of the pure Nafion membrane. A MOF containing a nitro functional group was first doped into Nafion in this study and exhibited excellent performance for improving composite membrane proton conductivity. This study will provide a valuable reference for designing different functionalized MOFs to promote the proton conductivities of proton exchange membranes.

A simple MOF constructed using Pb(ii) with strong polarizing force: a filler of Nafion membrane to increase proton conductivity

“…This phenomenon agrees with some reported composite membranes incorporating MOFs. 30,35,39 It has been interpreted that doping of these MOFs can improve the σ H+ of membranes and that the decreasing σ H+ value at relatively higher MOF doping amounts was caused by the -SO 3 H groups of Nafion being partially buried and the proton transfer pathway being interrupted or the aggregation phenomenon of MOF particles. For Pb-MOF, when the doping amount was 7%, the σ H+ value of the composite membrane was highest and 2.14 times that of the pure Nafion membrane at 353 K. The improvement degree of Pb-MOF/Nafion-7 obtained in this work was higher than that of most reported Nafion composition membranes doped with MOFs modified by -SO 3 H, -COOH, -NO 2 , etc.…”

Droplet‐Based Millifluidic Synthesis of a Proton-Conducting Sulfonate Metal–Organic Framework

“…All EIS and CV measurements were performed 30 min after the testing temperature reached the set value. Before resistance testing, the membrane was placed in a 95% relative humidity (RH) chamber (Memmert HCP150) at room temperature for 12 h to fully hydrate the membrane, matching commonly applied RH equilibration conditions prior to testing [67,68]. Fig.…”

Pore size effects on high-efficiency proton conduction in three stable 3D Al-based MOFs modified with imidazole

“…19,20 Imidazole (Im) molecules are good proton carriers and can be immobilized into porous MOFs to promote proton conductivity, which has become a general strategy for improving the proton conductivities of materials. 21 There are two approaches to loading imidazole molecules into MOFs. The first approach is introducing imidazole molecules into the frameworks of MOFs by chemically coordinated bonding with central metal ions or metal clusters.…”