Rationally Fabricating Three-Dimensional Covalent Organic Frameworks for Propyne/Propylene Separation

Efficient propyne/propylene separation to obtain polymer-grade propylene is a crucial and challenging process in industrial production, but it has not yet been realized in the covalent organic framework (COF) field. Addressing this challenge, we synthesize two three-dimensional COF adsorbents via a [8 + 4] construction approach based on an octatopic aldehyde monomer. Upon using the continuous rotation electron diffraction technique and structural simulation, both COFs are successfully determined as rare flu topology. Various characterization techniques prove that both COFs exhibit high crystallinity, high porosity, and good stability. Attributed to their interconnected micropores and nonpolar pore environment, these COFs can efficiently remove trace amounts of propyne from the propyne/propylene (1/99, and 0.1/99.9, v/v) mixture to obtain high-purity propylene (>99.99%), validated by dynamic breakthrough experiments. This work paves a new avenue for propyne/propylene separation using COFs as highly efficient adsorbents.