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 (O= 9.9 × 10-4 S cm -1) and anhydrous state (O= 6.7 × 10-5 S cm -1). This report constitutes the first emergence of COFs as proton conducting materials.