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Non-thermal plasma Methane capture Carbon dioxide capture Metal organic framework Methanol synthesis Atmospheric remediation 1. Introduction The stabilization of CO2 and CH4 concentrations in the air to control global warming is accelerating. There are continued efforts to develop and optimize different technologies for capture and sequestration of these greenhouse gases from industrial emission sites. From these gases, CH4 is the most dominant anthropogenic greenhouse gas (after CO2). Methane can react with nitrogen oxides leading to tropospheric ozone pollution and posses a higher global warming potential (GWP) than CO2. It is 84 times more potent than CO2 over the first 20 years after release and ~28 times more potent after a century. Methane concentrations could be restored to preindustrial levels by removing ~3.2 of the 5.3 Gt of CH4 currently in the atmosphere [1]. Rather than capturing and storing the methane, CH4 could be oxidized to CO2, through the ther- modynamically favorable reaction: CH4 + 2O2 → CO2 + 2H2O; ΔHrx = –803 kJ mol–1. With the possible production of valuable condensates such as form- aldehyde and methanol when employing different reaction conditions (i. e., gas ratio, oxidant type, temperature) and rational selected catalysts. The large activation barrier associated with splitting methane’s C– H * Corresponding author. E-mail address: Maria.CarreonGarciduenas@sdsmt.edu (M.L. Carreon). https://doi.org/10.1016/j.jcou.2021.101642 The direct capture of CO2 and CH4 from the atmosphere to stabilize the concentrations in the air to control global warming is accelerating. There are continued efforts to develop and optimize different technologies for capture and sequestration of these greenhouse gases from industrial emission sites. In this work we employed MOF-177 as an efficient CO2 and CH4 adsorbent at standard temperature and pressure conditions. We demonstrated the possibility of desorbing the gases under study when employing gentle plasma pulses of He. Moreover, we per- formed the synthesis of methanol from CH4 using O2 and CO2 as oxidants respectively in the presence of MOF- 177. We observed the highest conversion for the CH4 + O2 system when employing the MOF-177 at (5:1) (CH4: O2) flow ratio of 23.5 % and methanol selectivity of 17.65 %. While the best performance for the CH4 + CO2 system at the same conditions i.e., (5:1) (CH4: O2) flow ratio was 18.4 % for the methane conversion and 11.68 % for the selectivity towards methanol. We expect this preliminary understanding of the adsorption-reaction system under non-thermal plasma environment can lead to future atmospheric remediation technologies. 

Microporous crystals have emerged as highly appealing catalytic materials for the plasma catalytic synthesis of ammonia. Herein, we demonstrate that zeolitic imidazolate frameworks (ZIFs) can be employed as efficient catalysts for the cold plasma ammonia synthesis using an atmospheric dielectric barrier discharge reactor. We studied two prototypical ZIFs denoted as ZIF-8 and ZIF-67, with a uniform window pore aperture of 3.4 Å. The resultant ZIFs displayed ammonia synthesis rates as high as 42.16 μmol NH3/min gcat. ZIF-8 displayed remarkable stability upon recycling. The dipole−dipole inter- actions between the polar ammonia molecules and the polar walls of the studied ZIFs led to relatively low ammonia uptakes, low storage capacity, and high observed ammonia synthesis rates. Both ZIFs outperform other microporous crystals including zeolites and conventional oxides in terms of ammonia production. Furthermore, we demonstrate that the addition of argon to the reactor chamber can be an effective strategy to improve the plasma environment. Specifically, the presence of argon helped to improve the plasma uniformity, making the reaction system more energy efficient by operating at a low specific energy input range allowing abundant formation of nitrogen vibrational species. KEYWORDS: nonthermal plasma, plasma catalysis, ammonia synthesis, zeolitic imidazolate frameworks, ammonia adsorption effect