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.

• DO
  Department of Science and Technology, Ministry of Science and Technology, India

  Award: SB/SI/IC-32/2013
• CO
  Council of Scientific and Industrial Research, India

  Awards: CSC0102, CSC0122
• UG
  University Grants Commission