Modulating the Pore Environment of a Hydrogen-Bonded Organic Framework for Efficient Separation of a Ternary Mixture of Methanol-to-Olefin Products.

Developing energy-efficient adsorbents for one-step purification of ethylene (C2H4) from ternary methanol-to-olefins (MTO) product mixture remains highly important but essentially unexplored in hydrogen-bonded organic frameworks (HOFs). Herein, an ultramicroporous HOF, HOF-36, with pyridine-functionalized pore surfaces, was synthesized from 4,4',4″,4‴-(pyridine-2,3,5,6-tetrayl)tetrabenzoic acid. According to the single-component sorption isotherm, the activated HOF-36 (HOF-36a) exhibits preferential adsorption toward ethane (C2H6) and propylene (C3H6) over C2H4, with IAST selectivities of 1.6 for C2H6/C2H4 and 13.1 for C3H6/C2H4 mixtures at 298 K, where the C3H6/C2H4 selectivity surpasses those of all previously reported HOFs. Dynamic breakthrough experiments demonstrate that HOF-36a enables one-step purification of polymer-grade C2H4 (≥ 99.99%) from binary and ternary MTO-related hydrocarbon mixtures. Notably, HOF-36a affords a C2H4 productivity of 1.1 L kg-1 for the challenging ternary C3H6/C2H6/C2H4 (33.3/33.3/33.3, v/v/v) mixture. Moreover, the separation performance remains nearly unchanged under humid conditions and repeated breakthrough cycles. Theoretical calculations reveal that the pyridine-functionalized pore surface strengthens the binding affinity toward C2H6 and C3H6 through enhanced host-guest interactions. This work demonstrates the potential of HOFs for challenging multicomponent olefin separation and highlights pore environment engineering for regulating host-guest interactions.