Combination of Low-Polar and Polar Binding Sites in Aliphatic MOFs for the Efficient C 2 H 6 /C 2 H 4 Separation.

The selective capture of C 2 H 6 from C 2 H 6 /C 2 H 4 mixtures is of critical importance to realize the efficient one-step purification of C 2 H 4 but remains challenging due to their similar properties and smaller quadrupole moment of C 2 H 6 that usually result in C 2 H 4 -preferring adsorption. Herein, we reported two isostructural pillared-layer metal-organic frameworks, ZUL-C3 and ZUL-C4, which were constructed by mixed polycycloalkane-type ligands. Their low-polar pore environment along with more accessible low-polar C-H binding sites on the pore surface are conducive to generate more van der Waals interactions with C 2 H 6 while the carboxylic groups distributed at four corners of pores form stronger and more dipolar interactions with C 2 H 6 , cooperatively resulting in a good C 2 H 6 /C 2 H 4 uptake ratio of 1.50 for ZUL-C3 and 1.72 for ZUL-C4 in static adsorption experiments and a high C 2 H 4 (>99.99% purity) productivity of 10.1 L/kg for ZUL-C3 and 14.6 L/kg for ZUL-C4 from an equimolar C 2 H 6 /C 2 H 4 mixture in breakthrough experiments.