Tuning the FeII/FeIII ratio by substituent regulation to enhance the peroxidase-like activity of metal-organic frameworks for sensitive biosensing.

Here, electron-donating and electron-withdrawing substituents were introduced into MIL-88 (Fe) to regulate the electronic properties of the substituents. Benefiting from the influence of electron transfer and adsorption, the electron-donating (-NH2) substituent could significantly enhance the peroxidase-like activity of MIL-88 (Fe) due to the lowest energy change in the rate-determining step.