Effect of the Number of Methyl Groups in DMOF on N₂O Adsorption and N₂O/N₂ Separation

Nitrous oxide (N₂O), as the third largest greenhouse gas in the world, also has great applications in industry, so the purification of N₂O from N₂ in industrial tail gas is a crucial process for achieving environmental protection and giving full play to its economic value. Based on the polarity difference of N₂O and N₂, N₂O adsorption was researched on DMOF series materials with different polarities and methyl numbers of the ligand. N₂O adsorption at 0.1 bar is enhanced, attributed to an increase of the methyl group densities at the benzenedicarboxylate linker. Grand canonical Monte Carlo simulations demonstrate the key role of methyl groups within the pore surface in the preferential N₂O affinity. Methyl groups preferentially bind to N₂O and thus enhanced low (partial) pressure N₂O adsorption and N₂O/N₂ separation. The result shows that DMOF-TM has the highest N₂O adsorption capacity (19.6 cm³/g) and N₂O/N₂ selectivity (23.2) at 0.1 bar. Breakthrough experiments show that, with an increase of the methyl number, the coadsorption time and retention time also increase, and DMOF-TM has the best N₂O/N₂ separation performance.