Selective adsorption and separation of pyridine and picoline using hybrid[3]arene-based nonporous adaptive crystals

Abstract

The separation of pyridine and picoline is crucial and challenging. However, traditional separation methods are complicated and energy-consuming. Here, we present an efficient and simple approach using nonporous adaptive crystals of hybrid[3]arene H (Hα) to remove picoline from pyridine and picoline mixtures. Hα can separate 2-picoline from a 2-picoline/pyridine (1:1, v/v) mixture with 89.94% purity, 3-picoline from a 3-picoline/pyridine (1:1, v/v) mixture with 93.85% purity, and 4-picoline from a 4-picoline/pyridine (1:1, v/v) mixture with 96.05% purity, respectively. The single crystal structures combined with density functional theory calculations show that the selectivity of Hα comes from the stability of the host–guest complexes that adsorb preferred guest molecules. Besides, Hα can still adsorb picoline without reducing the selectivity for picoline after multiple desorption cycles, which shows excellent recyclable performance.