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.