One‐Step Separation of Propylene From Ternary C ₃ Mixtures in Amino Acid Functionalized Metal–Organic Frameworks

The low‐cost C 3 H 8 /C 3 H 6 /C 3 H 4 separation for high‐grade C 3 H 6 is of paramount importance but extremely difficult in the chemical industry. Here we report an economic strategy of functionalizing Zr‐based metal–organic frameworks (MOFs) with amino acids for one‐step C 3 H 6 purification from ternary C 3 mixtures. The resulting UiO‐67‐AA exhibits exceptionally high C 3 H 8 and C 3 H 4 uptakes and benchmark selectivities for C 3 H 8 /C 3 H 6 and C 3 H 4 /C 3 H 6 separations, rivaling reported ternary C 3 separating MOFs. Breakthrough experiments confirm its excellent performance in producing high‐purity C 3 H 6 in one step. Crucially, the estimated over 2250 times the cost reduction among reported C 3 H 8 /C 3 H 4 ‐selective MOFs makes UiO‐67‐AA an ideal candidate for industrial C 3 H 6 purification. In situ infrared spectroscopy, in situ neutron powder diffraction, and theoretical calculations indicate that amino acids offer selective binding to dually strengthen both C 3 H 8 and C 3 H 4 affinity over that of C 3 H 6 , with the amino group dictating the supramolecular interactions. Systematic evaluation across UiO‐67 with diverse nitrogen moieties establishes a monotonic relationship between the separation performance and the specific nitrogen electronegativity, providing an element‑specific and quantitative electronegativity‐driven design rule for next‐generation MOF adsorbents for industrial olefin purification.