Metal–Organic Framework with Lewis Basic N-Rich Channels for Separating Hydrocarbons from CO ₂ -Containing Mixtures

Carbon dioxide-assisted oxidative dehydrogenation of propane (C3H8, CO2–ODHP) is an emerging energy-efficient route for propylene (C3H6, a critical cornerstone petrochemical) production. However, its effluent contains a diluted C3H6/C3H8 mixture alongside unreacted CO2, necessitating an efficient separation to obtain a C3-enriched stream suitable for subsequent upgrading. In this study, we first propose this separation concept and realize it through adsorption technology by developing a promising adsorbent tailored for this purpose. Specifically, we report a nitrogen-rich, water-stable novel metal–organic framework (MOF), TJU-106, engineered for this separation, whose high density of Lewis basic nitrogen sites provides an intrinsic C3-favoring adsorption. Following the successful synthesis, we conducted postsynthetic metalation to create additional metal sites within the pores, further enhancing its uptake and adsorption kinetics, as observed in the best-performing Ni-TJU-106 (nickel-incorporated TJU-106). Breakthrough experiments in a dynamic C3H6/C3H8/CO2 stream confirm its excellent performance in selectively capturing C3H6 and C3H8 from CO2-containing mixtures with good regenerability. In situ Diffuse reflectance infrared Fourier transform spectroscopy (DRIFTs) and Density Functional Theory (DFT) studies reveal that adsorption occurs primarily at the N sites in the parent MOF, while subsequent Ni metalation introduces π-complexation interactions with C3 hydrocarbons. Notably, these Ni sites interact weakly with CO2, which underpins the selective adsorption of C3 hydrocarbons. This work establishes a nitrogen-site-enabled metalation strategy to create C3-selective adsorption domains, offering a practical and tunable materials blueprint for the critical downstream purification in CO2–ODHP processes.