Binuclear copper catalytic sites confined in a metal-organic framework for monooxygenase-mimetic C(sp3)–H oxidation

Abstract

The ultimate catalytic activity of metalloenzymes relies on both primary and secondary coordination spheres of the active site, which is hard to mimic in synthetic catalytic systems. Introduction of flexible tetramethylethylenediamine (TMEDA) side chains to a UiO-67 metal-organic framework (MOF) enables the installation of non-covalently interacted, self-adaptive binuclear copper sites that synergistically activate O₂, and the confined MOF pore space rich in aromatic functionalities engages organic substrates through multiple non-covalent interactions. Taking advantage of both structural features, the resulting UiO-67-TMEDA-Cu catalyst replicates the catalytic pocket of methane monooxygenase and drives aerobic C(sp³)–H oxidation under mild, additive-free conditions, exhibiting activity significantly surpassing that of its mononuclear analog and a homogeneous binuclear control catalyst lacking spatial confinement. Kinetic studies and theoretical calculations revealed that the binuclear copper pair catalyst exhibited higher activity than its mononuclear counterpart by lowering the energy demands of O–O bond cleavage and hydrogen atom abstraction, while the MOF cavity further reduces the binding energy between organic substrates and Cu₂ sites. This work thus demonstrates the great potential of engineering non-covalently interacted, synergistic metal pairs within MOFs to achieve enzyme-like selectivity and activity for advanced catalytic transformations.