Reversing adsorption and separation of 1-phenylethanol and acetophenone in organic phase via β-ketoenamine-linked covalent organic frameworks

Adsorption is considered as a promising method to purify the mixed acetophenone (AP) and 1-phenylethanol (1-PE) that are generally difficult to separate. Many efforts have been made to improve the preferential uptake of AP over 1-PE in aqueous phase, but there exists a practical bottleneck associated with their limited aqueous solu-bility. Herein, we demonstrate unprecedented reversal of selectivity in the organic medium enabled by beta-ketoenamine-linked covalent organic frameworks (COFs), which were fabricated successfully by poly-condensation between 1,3,5-triformylphloroglucinol (Tp) and diamines. The dependence of selective adsorption ability toward 1-PE on pore size was firstly investigated experimentally, indicating that TpBZ-COF with moderate pore size outperformed other analogues. The adsorption behaviors of 1-PE and AP onto TpBZ-COF were examined systematically. The evaluation results revealed a strong affinity toward 1-PE versus AP as well as excellent stability in recycling experiments. Further, the dynamic breakthrough experiments confirmed the practical application potential and remarkable recyclability. To probe the mechanism and structure-activity relationship, an imine-linked COF possessing similar porous structure was used as a reference for comparison of separation performance both experimentally and theoretically. The occurrence of hydrogen bonding between the hydroxyl of 1-PE and beta-ketoenamine-linkage as H-bond acceptor in suitable pore spaces endows TpBZ-COF a fantastic candidate for purifying 1-PE and AP from petrochemical by-products.