Hyper-Cross-Linked Polymers for the Capture of Aromatic Volatile Compounds

Hyper-cross-linked porous polymers (HCPs) are proposed as sorbents for the removal of aromatic volatile pollutants by using toluene as a representative of the BTX family. The hierarchical (micro and meso) porous architecture of the HCPs has been established by N2 physisorption at 77 K while the toluene adsorption capacities were determined by volumetric adsorption at 308 K. The HCPs display very high toluene uptakes, reaching adsorption capacities as high as 154% in weight for the polymer obtained with a tetraphenylmethane (TPM) and a formaldehyde dimethyl acetal (FDA) ratio of 1/16, whereas only very low uptakes were observed for aliphatic molecules such as n-hexane. HCP materials experience swelling effects evaluated by comparing the volume assessed via N2 physisorption with the volume occupied by toluene molecules in volumetric adsorption experiments. A multispectroscopic approach involving FT-IR and solid-state NMR techniques gave direct proof of the close spatial proximity between the polymeric host framework and guest BTX molecules. Solid-state 1H and 13C NMR spectroscopies have unambiguously identified the presence of CH/π interactions between the guest molecules and the porous framework of the hyper-cross-linked polymers.