Constructing Biomimetic Channels in Hydrogen-Bonded Organic Framework via Post-Synthesis for Enhanced Proton Conductivity.

Proton transport channels in biological systems are constructed by the specific amino acid residues with hanging carboxylic acid groups acting as proton donors and acceptors, enabling rapid proton conduction via the Grotthuss mechanism. Hydrogen-bonded organic frameworks (HOFs) are promising candidates for artificially simulating proton channels due to their designable structure and abundant proton sources in the network. However, these protons were usually immobilized within hydrogen bonds between two building blocks, which require a high energy barrier for initiating proton transport. Post-synthetic modification (PSM) may be a viable solution to the above problems but has yet to be achieved in HOFs. Herein, we demonstrate for the first time that unoccupied carboxylic acid groups can be created through post-synthesis which further stabilizes water molecules to construct continuous proton channels, bringing boosted proton conductivity by three orders of magnitude. The structure transformation process and the intermediate can be identified clearly by crystallography with an unveiled mechanism. This work offers a new approach to constructing biomimetic channels for proton conduction and HOF functionalization.