Ultrahigh Proton Conductivities of Postmodified Hf(IV) Metal–Organic Frameworks and Related Chitosan-Based Composite Membranes

Abstract

Recently, researchers have focused on preparing and studying proton exchange membranes. Metal−organic frameworks (MOFs) are candidates for composite membrane fillers due to their high crystallinity and structural characteristics, and Hf-based MOFs have attracted our attention with their high porosity and high stability. Therefore, in this study, Hf-based MOFs were doped into a costeffective chitosan matrix as fillers to fabricate composite films having excellent proton conductivity (σ). First, the nanoscale MOFs Hf-UiO-66-(OH) 2 (1) and Hf-UiO-66-NH 2 (2) were chemically modified by a ligand design strategy to obtain SA-1 and CBD-2 bearing free −COOH units. The proton conductivities of SA-1 and CBD-2 under optimal test conditions reached 1.23 × 10 −2 and 0.71 × 10 −2 S cm −1 . After that, we prepared composite membranes CS/SA-1 and CS/ CBD-2 by the casting method; tests revealed that the introduction of MOFs improved the stabilities and σ values of the membranes, and their best σ could reach above 10 −2 S cm −1 under 100 °C/98% RH. Further structural characterization and activation energy calculation revealed the conductive mechanism of the composite films. This investigation not only proposes a novel chemical modification method for optimizing the σ of MOFs but also promotes the development of MOF-doped composite membranes and provides a basis for future applications of MOFs in fuel cells.

A stable Mn(ii) coordination polymer demonstrating proton conductivity and quantitative sensing of oxytetracycline in aquaculture

“…56 The abundantly adsorbed water molecules at high RH work as proton carriers on the surface of Mn-CP absorbing heat and ionizing into hydration ions (H 3 O + ), realizing the protons transfer. 57 The PXRD patterns and IR spectra after conductivity are in accordance with the simulated ones, proving that the structure of Mn-CP is stable during the proton conduction measurement process (Fig. 2c and d).…”

Comparative Study on the Proton Conduction Behaviors of Two Acidic Amphiphilic and Hydrophilic Coordination Compounds in Nafion Composite Membranes

“…The σ H+ value of the composite membrane initially increases and then decreases with increasing doping amount, consistent with trends observed in other reported composite membranes doped by MOFs or CPs particles. This phenomenon is attributed to particle aggregation at higher doping amounts leading to a decrease in σ H+ value. − Therefore, determining the optimal doping amount is crucial for Nafion composite membrane studies. For H 4 (Co-L1), the optimal doping amount is 2%, resulting in a 1.5-fold increase in σ H+ compared to pure Nafion membranes.…”

Icing on the Cake: Imidazole-Anchored Strategy To Enhance the Proton Conductivity of Two Isostructural Ce(IV)/Hf(IV) Metal–Organic Frameworks

“…For instance, in 2021, Bao et al presented a proton-conductive phosphonate-based Hf-MOF and the changes in proton conductivity after loading different guest molecules . Recently, our group has investigated several proton-conductive Hf-MOFs based on different organic linkers, such as terephthalic acid, 2,5-dihydroxyterephthalic acid, 2-aminoterephthalic acid, , fumaric acid, 2,5-thiophene dicarboxylic acid, and 2,5-furandicarboxylic acid . It was discovered that their optimal σ values are in the range 10 –3 –10 –2 S·cm –1 .…”