Solar-hybrid biocatalyst for methane hydroxylation to methanol.

Abstract

Methane hydroxylation presents a promising approach to produce high-energy methanol from potent greenhouse gases, thereby contributing to a more sustainable future. Despite its environmental importance, current research on this process remains challenging due to the harsh operating conditions for the activation of inert C-H bond in methane. In nature, methane monooxygenase converts methane by activating the C-H bonds through its hydroxylase, under ambient conditions, receiving electrons from NADH via a reductase. Beyond the traditional biological approach, the development of NADH-independent biocatalytic systems could open new avenues for cost-effective and sustainable methane conversion. Herein, we report an NADH-free biosolar platform that activates hydroxylase for eco-friendly methanol production. The xanthene-based light harvester spontaneously associates with hydroxylase and directly transfers its photoexcited electrons to the diiron active site, eliminating the need for a cofactor or reductase. Halogenation of xanthene accelerates direct electron transfer to the active site by increasing the polarizability and spin-orbit coupling of the light harvesters. Accordingly, the direct photobiocatalytic platform achieved a methanol time yield of 7.52 mmol g_cat^-1 h^-1. This work provides the design concept of solar-driven biocatalytic methane hydroxylation under ambient conditions, suggesting a promising approach for implementing methanol biomanufacturing.