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

Conversion of methane (CH₄) to ethylene (C₂H₄) and/or acetylene (C₂H₂) 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 CH₄ controllably, and separating C₂₊ products from unreacted CH₄ can be challenging. Here, we report the direct conversion of CH₄ to C₂H₄ and C₂H₂ 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 C₂H₄ and C₂H₂ reaches 96% with a high time yield of 334 μmol g_cat^-1 h^-1. At a conversion of 10%, the selectivity to C₂₊ hydrocarbons and time yield exceed 98% and 2056 μmol g_cat^-1 h^-1, respectively, representing a new benchmark for conversion of CH₄. 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 CH₄ and stabilizing reaction intermediates via the formation of an Fe-O(CH₃)-Fe adduct. In addition, a cascade fixed-bed system has been developed to achieve online separation of C₂H₄ and C₂H₂ from unreacted CH₄ for direct use. Integrating the processes of CH₄ 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.