A Radical Twist to the Versatile Behavior of Iron in Selective Methane Activation**

The availability of large reserves of methane, which is the main component of most natural gas, makes it a very important feedstock molecule for the production of base chemicals (e.g. ethylene, propylene, and aromatics) and energy carriers (i.e. transportation fuels). More recently, the shale gas bonanza—particularly in the USA—as well as the presence of vast amounts of gas methane hydrates at several places on earth, has further spurred great interest to develop economically viable, large-scale routes for the selective activation of methane. Current commercial routes for methane activation involve the conversion of methane into syngas, which is a mixture of CO and H2, and its subsequent conversion into hydrocarbons such as propylene, aromatics, and fuels. More specifically, methanol-to-hydrocarbon (MTH) catalysis involves the catalytic conversion of syngas-derived methanol (or dimethyl ether) into mixtures of, for example, ethylene, propylene, and aromatics, depending on the specific zeolite material and reaction conditions applied. On the other hand, one can make use of the syngas produced from methane and convert it with either ironor cobalt-based Fischer–Tropsch synthesis (FTS) catalysts into, for example, waxes, which can then be backcracked into chemicals and transportation fuels, such as diesel, with zeolite-based catalysts. Unfortunately, both syngas conversion routes are complex multistep catalytic operations, which are energy intensive, due to, for example, the syngas generation, costly in terms of the different reaction and separation steps involved, and far from optimal in terms of atom efficiency. In view of these inherent disadvantages, researchers both in academia and industry are searching for more costand resource-effective routes for the direct utilization of methane. An example of such an approach is the oxidative coupling of methane (OCM), generating methyl radicals in the gas phase which then recombine to ethylene. Unfortunately, the currently developed OCM catalyst materials and related reactor (membrane) designs do not provide the required performance, both in terms of activity and more importantly selectivity (e.g. CO2 generation and formation of coke deposits). However, in recent announcements, companies like Siluria and UOP report on the (pre)-commercialization of methane coupling routes to ethylene. In a recent study, Guo and co-workers reported on a new catalyst material, which could circumvent the disadvantages of, for example, OCM technology. It was found that the novel catalyst, consisting of lattice-confined single iron sites (Figure 1), produces in a nonoxidative manner high yields of ethylene, benzene, and naphthalene. Very remarkable is the negligible amount of coke deposits formed at the relatively high operational temperature of 1363 K, which results in an