Catalytic Gas-Driven Exfoliation of Sulfonic Acid-Linked Covalent Organic Framework Nanostructures for Hydrogen Sensing

Exfoliating bulk covalent organic frameworks into soluble covalent organic nanosheets (CONs) enhances processability. Utilizing the catalytic ability of −SO3H groups, ammonia borane hydrolysis was performed in the pores of a TpPa-SO3H COF (Tp = 1,3,5-triformylphloroglucinol; Pa-SO3H = 2,5-diaminobenzenesulfonic acid). The in situ generated hydrogen converted bulk powders into CONs (thickness = 4–16 nm). The CONs-based H2 sensor showed a response of 12.5 ± 0.6% and response/recovery times of 5.5 ± 1/2.6 ± 0.5 s, respectively, at 120 °C for 1% H2. The sensor offers quicker response and recovery times compared to nonmetallic H2 sensors like polyaniline and polythiophene.