Viewpoint on the Partial Oxidation of Methane to Methanol Using Cu- and Fe-Exchanged Zeolites

Biologically derived methane monooxygenase proteins (MMO) transform CH₄ and O₂ into methanol with remarkable selectivity. MMO possess two key features that result in selective methanol production: (1) ligand fields that induce high-spin electronic configurations at the transition metal sites, which induce highly reactive oxidative and reductive environments and (2) a complex gating mechanism that influences the lability and dynamic binding of reagents to the active site, which enables methanol transport out of the active site pocket while also forbidding back diffusion. Both aspects of the enzymatic system are described in the context of replicating them in synthetic catalysts. First, the ability of zeolites to share many of the same attributes in terms of site isolation and ligand field strength with metalloenzymes is discussed. Second, an overview of the current understanding regarding the transport mechanism in MMO for protecting methanol from further oxidation and enabling 100% selectivity to methanol formation is provided along with an outlook on future directions and potential strategies to combine these features in a truly biomimetic synthetic platform.