Moderately polarized carborane-MOF with inverse C2 selectivity for one-step polymer-grade ethylene purification.

Ethylene purification from ternary C2 mixtures (C2H2/C2H4/C2H6) typically requires multi-step processes due to competing adsorption mechanisms in conventional adsorbents. Herein, we report a carborane-based metal-organic framework (CB-Zn-DPG) featuring moderately polarized pore surfaces that inverts traditional selectivity trends. Unlike polar MOFs (C2H2 > C2H4 > C2H6) or nonpolar MOFs (C2H6 > C2H4 > C2H2), CB-Zn-DPG simultaneously captures both C2H2 (61.5 cm3 g-1) and C2H6 (44.0 cm3 g-1) preferentially over C2H4 (42.4 cm3 g-1) at 298 K and 1.0 bar, with higher isosteric heats for impurities (C2H2 31.5 kJ mol-1; C2H6 29.8 kJ mol-1vs. C2H4 25.9 kJ mol-1). DFT calculations reveal multi-site van der Waals interactions at the channel centers for C2H2/C2H6, while C2H4 adsorbs weakly at the pore corners. Dynamic breakthroughs confirm direct production of >99.99% polymer-grade C2H4 from equimolar C2H4/C2H6 (50/50) and ternary C2H2/C2H4/C2H6 (1/90/9) mixtures in a single column operation. This work establishes pore-surface polarity engineering as a paradigm for challenging hydrocarbon separations.