Iron-porphyrin-based covalent-organic frameworks for electrochemical sensing H2O2 and pH

Here, a novel iron-porphyrin-based covalent organic framework (COFp-Fepor NH2-BTA) was synthesized and applied for electrochemical sensing H2O2 and pH which involved in many biological processes. The COFp-Fepor NH2-BTA was obtained by post-modification of porphyrin-based COF (COFp-por NH2-BTA) which was firstly synthesized by aldehyde-ammonia condensation reaction between 1,3,5-benzenetricarboxaldehyde and 5,10,15,20-tetrakis(4-aminophenyl)-21H,23H- porphine. The COFp-por NH2-BTA was proved to be regular and uniform spherical particles with diameter about 1 μm, as well as possessed good crystalline structure and abundant micropores of about 1.4 nm. The resulted COFp-Fepor NH2-BTA after post-modification with Fe2+ maintained the original shape and crystalline structure of COFp-por NH2-BTA, while the micropores decreased to be about 0.89 nm. Electrochemical results indicated that the synthesized COFp-Fepor NH2-BTA had good electrochemical redox and proton activity owing to iron-porphyrin, enabling to simultaneously be used as mimic peroxidase to catalyze the reduction of hydrogen peroxide (H2O2) and evaluate pH using current and potential as signal, respectively. The prepared sensor showed good performance for H2O2 detection from 6.85 nM to 7 μM with the detection limit of 2.06 nM (S/N = 3), and pH test from 3.0 to 9.0. This work demonstrated that the iron-porphyrin-based COF could be used as a mimic peroxidase to apply in biological fields.