Inverse Hydrocarbon Recognition via Nitro Group–Programmed Soft Porous Crystal for One-Step C3H6 Purification

The energy-intensive separation of propylene (C3H6) from propane (C3H8) is a major industrial challenge. To address this, we introduce a concept of molecular recognition based on hydrogen atom content (Hδ+) using cooperative host–guest interactions in soft porous crystals. Guided by this principle, we designed a flexible porous crystal, NTU-99-NO2, incorporating electronegative nitro group receptors into a dynamic framework. This material exhibits unprecedented inverse selectivity: a 2-fold higher uptake of C3H8 over C3H6 at 298 K, 1 bar. Crystallographic, theoretical, and in situ studies reveal that only C3H8 triggers pore expansion and secondary adsorption, enabled by nitro group-mediated recognition. Comparative studies with hydroxyl- and methyl-functionalized analogs confirm the crucial role of receptor electronegativity. NTU-99-NO2 enables the direct, one-step production of polymer-grade C3H6, combining breakthrough selectivity, structural adaptability, and scalable synthesis. This work establishes a generalizable design strategy for adaptive, receptor-guided separations in porous materials.