Abstract
The conductivity performance of a new series of chemically stable proton conducting Metal Organic Frameworks (MOFs) as well as a superionic molecular crystal was explored. The contribution of this PhD was to (i) select a variety of architectures and functionalities of robust MOFs/superionic molecular solids and (ii) characterize and rationalize their conducting performance over various temperature/humidity conditions. We designed two series of MOFs to achieve promising proton-conducting performance, using distinct approaches to modulate the concentration of Brønsted acidic sites and charge carriers and further boost the conductivity properties. First, a multicomponent ligand replacement strategy was successfully employed to elaborate a series of multivariate sulfonic-based solids MIP-207-(SO3H-IPA)x-(BTC)1–x which combine structural integrity with high proton conductivity values (e.g., σ = 2.6 × 10–2 S cm–1 at 363 K/95% Relative Humidity -RH-). Secondly, a proton conducting composite was prepared through the impregnation of an ionic liquid (1-Ethyl-3-methylimidazolium chloride, EMIMCl) in the mesoporous MIL-101(Cr)-SO3H. The resulting composite displaying high thermal and chemical stability, exhibits outstanding proton conductivity not only at the anhydrous state (σ473 K = 1.5 × 10-3 S cm-1) but also under humidity (σ(343 K/60%-80%RH) ≥ 0.10 S cm-1) conditions. Finally, the ionic conducting properties of another class of porous solids, considering a zirconium-formate molecular solid containing KCl ion pairs (ZF-3) were explored. ZF-3 switches from an insulator (σ = 5.1 x 10-10 S cm-1 at 363 K/0% RH) to a superionic conductor upon hydration (σ = 5.2 x 10-2 S cm-1 at 363 K/95 % RH), in relation with the boost of Cl- dynamics upon water adsorption. Noteworthy, quantum- and force-field based simulations were combined with the experimental approach to elucidate the microscopic mechanisms at the origin of the ionic conducting properties of the studied materials. This fundamental knowledge will serve to create novel robust superionic conductors with outstanding performances that will pave the way towards appealing societal applications for clean energy production.