Pore configuration control in hybrid azolate ultra-microporous frameworks for sieving propylene from propane

Abstract

Developing porous adsorbents for the complete sieving of propylene/propane mixtures represents an alternative method to energy-intensive cryogenic distillation processes. However, the similar physical properties of these molecules and the inherent trade-off among adsorption capacity, selectivity, diffusion kinetic and host–guest binding interactions in molecular sieving adsorbents makes their separation challenging. Here we report the separation of propylene/propane mixtures through a crystalline porous material (HAF-1) that features channels and shrinkage throats—the latter defined as narrower channels that connect the main channels and a molecular pocket—where the throat aperture is between the kinetic diameters of propylene and propane. Single-crystal X-ray diffraction and computational simulation reveal that the shrinkage channels and hanging molecular pockets are key to ensure high sieving efficiency and high propylene adsorption capacity. Dynamic breakthrough experiments show that HAF-1 enables the achievement of high-purity (≥99.7%) propylene with a productivity of 33.9 l kg⁻¹ by just one adsorption–desorption circle from propylene/propane mixtures.