Direct Conversion of Methane to Ethylene and Acetylene over an Iron-Based Metal-Organic Framework.

Conversion of methane (CH) to ethylene (CH) and/or acetylene (CH) enables routes to a wide range of products directly from natural gas. However, high reaction temperatures and pressures are often required to activate and convert CH controllably, and separating C products from unreacted CH can be challenging. Here, we report the direct conversion of CH to CH and CH driven by non-thermal plasma under ambient (25 °C and 1 atm) and flow conditions over a metal-organic framework material, MFM-300(Fe). The selectivity for the formation of CH and CH reaches 96% with a high time yield of 334 μmol g h. At a conversion of 10%, the selectivity to C hydrocarbons and time yield exceed 98% and 2056 μmol g h, respectively, representing a new benchmark for conversion of CH. In situ neutron powder diffraction, inelastic neutron scattering and solid-state nuclear magnetic resonance, electron paramagnetic resonance (EPR), and diffuse reflectance infrared Fourier transform spectroscopies, coupled with modeling studies, reveal the crucial role of Fe-O(H)-Fe sites in activating CH and stabilizing reaction intermediates via the formation of an Fe-O(CH)-Fe adduct. In addition, a cascade fixed-bed system has been developed to achieve online separation of CH and CH from unreacted CH for direct use. Integrating the processes of CH activation, conversion, and product separation within one system opens a new avenue for natural gas utility, bridging the gap between fundamental studies and practical applications in this area.