A metal–organic framework based propylene nano-trap with dual functionalities for highly efficient propylene/propane separation

Abstract

Propylene/propane (C₃H₆/C₃H₈) separation represents one of the most challenging and energy-intensive processes in the petrochemical industry due to their very similar sizes and physical properties. Most of the reported physisorbents still face the challenge of achieving simultaneously high C₃H₆ uptake and selectivity with moderate adsorption enthalpy. Herein, we realize an efficient propylene nano-trap in a microporous MOF (ZJUT-2, Ni(pyz-SH)₂SiF₆) for highly efficient C₃H₆/C₃H₈ separation. This MOF-based propylene nano-trap features a suitable pore cavity decorated with dual functionalities (–SH and SiF₆²⁻) to optimally interact with the C₃H₆ molecule, affording both large C₃H₆ capture capacity (123.5 cm³ cm⁻³ at 296 K and 0.5 bar) and high C₃H₆/C₃H₈ selectivity of 17.2 achieved with moderate C₃H₆ adsorption enthalpy (45 kJ mol⁻¹). Theoretical calculations revealed that the appropriate pore cavity and dual functionalities synergistically construct an efficient nano-trap to match better with the C₃H₆ molecule and thus provide stronger multipoint interactions with C₃H₆ over C₃H₈. Actual breakthrough experiments demonstrated that this material can efficiently capture C₃H₆ from C₃H₆/C₃H₈ mixtures (50/50 and 10/90, v/v) under ambient conditions, affording both top-tier C₃H₆ capture amount (2.6 mmol g⁻¹) and dynamic selectivity of 10.