A Trifluoromethyl-Functionalized Ni–MOF with Fluorinated Pore Surface for One-Step Purification of Polymer-Grade C2H4 from MTO Streams

Abstract

Abstract Efficient purification of polymer-grade ethylene (C2H4) from methanol-to-olefins (MTO) products remains challenging because of the similar physicochemical properties of light hydrocarbons. Herein, we report a fluorinated metal–organic framework, CF3-Ni, featuring uniformly distributed trifluoromethyl (−CF3) groups that construct a fluorine-rich polar pore environment for selective hydrocarbon recognition. CF3-Ni exhibits preferential adsorption toward C3 hydrocarbons, with an affinity sequence of C3H6 > C3H8 > C2H4. At 298 K and 1 bar, it shows a C3H6/C2H4 IAST selectivity of 9.3 and a moderate C3H6 adsorption enthalpy of 38.4 kJ mol–1, enabling strong yet reversible host–guest interactions. Breakthrough experiments demonstrate efficient separation of C3H6/C2H4 mixtures over a wide range of feed compositions, affording polymer-grade C2H4 (>99.95%) with a maximum productivity of 7.4 mol kg–1 and simultaneous recovery of high-purity C3H6. Notably, one-step purification of polymer-grade C2H4 is achieved from a ternary C3H6/C3H8/C2H4 mixture, even under humid and elevated-pressure conditions. DFT calculations and in situ FT-IR spectroscopy reveal that C–H···F interactions contribute to the preferential binding of C3H6. This work demonstrates fluorinated pore chemistry as an effective strategy for practical olefin purification.