Porous Organic Polymers Incorporating Shape-Persistent Cyclobenzoin Macrocycles for Organic Solvent Separation

Abstract

The recovery and separation of organic solvents is highly important for the chemical industry and environmental protection. In this context, porous organic polymers (POPs) have significant potential owing to the possibility of integrating shape-persistent macrocyclic units with high guest selectivity. Here, we report the synthesis of a macrocyclic porous organic polymer (np-POP) and the corresponding model compound by reacting the cyclotetrabenzil naphthalene octaketone macrocycle with 1,2,4,5-tetraaminobenzene and 1,2-diaminobenzene, respectively, under solvothermal conditions. Co-crystallization of the macrocycle and the model compound with various solvent molecules revealed their size-selective inclusion within the macrocycle. Building on this finding, the np-POP with a hierarchical pore structure and a surface area of 579 m² g⁻¹ showed solvent uptake strongly correlated with their kinetic diameters. Solvents with kinetic diameters below 0.6 nm – such as acetonitrile and dichloromethane – showed high uptake capacities exceeding 7 mmol g⁻¹. Xylene separation tests revealed a high overall uptake (~34 wt %), with o-xylene displaying a significantly lower uptake (~10 wt % less than other isomers), demonstrating the possibility of size and shape selective separation of organic solvents.