Pore Modulation of Hydrogen‐Bonded Organic Frameworks for Efficient Separation of Propylene

Abstract

Developing hydrogen‐bonded organic frameworks (HOFs) that combine functional sites, size control, and storage capability for targeting gas molecule capture is a novel and challenging venture. However, there is a lack of effective strategies to tune the hydrogen‐bonded network to achieve high‐performance HOFs. Here, a series of HOFs termed as HOF‐ZSTU‐M (M=1, 2, and 3) with different pore structures are obtained by introducing structure‐directing agents (SDAs) into the hydrogen‐bonding network of tetrakis (4‐carboxyphenyl) porphyrin (TCPP). These HOFs have distinct space configurations with pore channels ranging from discrete to continuous multi‐dimensional. Single‐crystal X‐ray diffraction (SCXRD) analysis reveals a rare diversity of hydrogen‐bonding models dominated by SDAs. HOF‐ZSTU‐2, which forms a strong layered hydrogen‐bonding network with ammonium (NH₄⁺) through multiple carboxyl groups, has a suitable 1D “pearl‐chain” channel for the selective capture of propylene (C₃H₆). At 298 K and 1 bar, the C₃H₆ storage density of HOF‐ZSTU‐2 reaches 0.6 kg L⁻¹, representing one of the best C₃H₆ storage materials, while offering a propylene/propane (C₃H₆/C₃H₈) selectivity of 12.2. Theoretical calculations and in situ SCXRD provide a detailed analysis of the binding strength of C₃H₆ at different locations in the pearl‐chain channel. Dynamic breakthrough tests confirm that HOF‐ZSTU‐2 can effectively separate C₃H₆ from multi‐mixtures.