The invention provides a catalytic system comprising a REDOX catalyst and a porous polymeric matrix wherein the porous polymeric matrix has pores with a size from 1 to 1000 nm and it is covalently functionalized with functional groups R1 or, alternatively, with functional groups R’1 and R2; the REDOX catalyst comprises an isoalloxazine moiety which has one or more functional groups R3; R1 and R2 are capable of forming non-covalent reversible interactions with R3; R1 and R2 are in a
molar concentration excess with respect to the molar concentration of the REDOX catalyst; and R1 and R’1 are electron donor or electron acceptor groups having a REDOX potential between +2.70 to -2.5 V as determined by cyclic voltammetry using an Ag/AgCl electrode as reference. The invention also provides processes for its preparation as well as kits and devices comprising the catalytic system, as well as its use in the fields of therapy and diagnostics.