Biomimetic Water-Stable Multicomponent HOFs as Ultrahigh Superprotonic Conductors

Hydrogen-bonded organic frameworks (HOFs) with abundant proton sources and directional water-mediated proton transport channels can mimic proton transfer relay as synthetic analogues to biochemical systems involving carboxylate, sulfonate as proton donors, and basic amino acids as acceptors. By employing a crystallization-guided regioselective protonation strategy, we have engineered two charge-assisted water stable HOFs─IITKGP-HOF-1 (with dual asymmetric heterocyclic core) and IITKGP-HOF-3 (with usual dual symmetric heterocyclic core)─to regulate proton transport channels. The improved alignment of protons with increased lattice water molecules in the former facilitated a long-range H-bonding network, culminating in ultrahigh superprotonic single crystal conductivity (5.29 × 10–2 S cm–1). Conversely, the lack of such an extended network in the latter (closed tunnels) resulted in 7000 times lower conductivity (7.6 × 10–6 S cm–1), further supported by in-depth simulation studies. IITKGP-HOF-1 demonstrates the pioneering example of a HOF (with asymmetric cores for multiple protonation within a single molecular tecton) displaying ultrahigh superprotonic conductivity with recyclable performances.