Magnetically tunable selectivity in methane oxidation enabled by Fe-embedded liquid metal catalysts.

As they are liquids at room temperature, gallium-based metal substrates allow catalytic metal atoms to move freely without lattice constraints, thereby facilitating the development of catalysts with reconfigurable structures. Here we design an iron-embedded liquid metal catalyst that enables reversible switching of the aggregation and electron spin of iron atoms by controlling an external magnetic field. This facilitates a reversible conversion of the primary liquid products, methyl hydroperoxide (CH3OOH) and acetic acid (CH3COOH), under ambient conditions. The catalyst achieves promising production rates (CH3OOH, 1,679.6  m m o l g F e - 1 h - 1 ; CH3COOH, 790.5  m m o l g F e - 1 h - 1 ) and high selectivities (CH3OOH, 99.9%; CH3COOH, 91.7%). In the absence of the magnetic field, iron atoms are atomically dispersed, leading to the C1 pathway without C-C bond coupling. When a magnetic field is applied, iron atoms cluster, favouring CH3COOH production in the C2 pathway. The product distribution can be finely and reversibly tuned with magnetic field intensity adjustments ranging from 0 to 500 G. Our findings highlight the potential for using an external magnetic field to precisely control catalytic pathways.