Phosphoric Acid Loaded Azo (−NN−) Based Covalent Organic Framework for Proton Conduction

Two new chemically
stable functional crystalline covalent organic
frameworkds (COFs) (Tp-Azo and Tp-Stb) were synthesized using the Schiff base reaction
between tri­formyl­phloro­glucinol (Tp) and 4,4′-azodi­aniline (Azo) or 4,4′-diamino­stilbene
(Stb), respectively. Both COFs show the expected keto-enamine
form, and high stability toward boiling water, strong acidic, and
basic media. H3PO4 doping in Tp-Azo leads to immobilization of the acid within the
porous framework, which facilitates proton conduction in both the
hydrous (σ = 9.9 × 10–4 S cm–1) and anhydrous state (σ = 6.7 × 10–5 S cm–1). This report constitutes the first emergence
of COFs as proton conducting materials.