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

Abstract

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.

Hyper Cross-Linked Polymers as Additives for Preventing Aging of PIM-1 Membranes

“…Towards higher values of P/P 0 a gradual increase in the amount of adsorbed nitrogen is observed indicating the filling of mesopores in the range between 0.45 and 0.8 P/P 0 . Open hysteresis loops for both materials are observed for the whole desorption branch, which is consistent with swelling effects of the polymeric network, due to gas sorption [36,37]. The non-reversible desorption at low relative pressures indicates that N 2 could either be trapped in pockets or free volume elements with a size comparable to that of the N 2 molecule, or swelling of ABT is locking some of the pockets or free volume elements on the time scale of the experiments, or in combination.…”

“…Between 3000 and 2800 cm −1 , the signals of aliphatic C-H stretching vibrations are found. In particular, the band at 2965 cm −1 is assigned to the C-H asymmetric stretching mode of methyl groups [ 37 , 39 , 40 ] while the band at 2922 cm −1 is assigned to the asymmetric stretching mode of the -CH 2 - group [ 39 , 40 ]. The corresponding symmetric stretching vibrations are found at 2870 cm −1 for the methyl group and at 2845 cm −1 for the methylene group [ 37 , 39 , 40 ].…”

“…In particular, the band at 2965 cm −1 is assigned to the C-H asymmetric stretching mode of methyl groups [ 37 , 39 , 40 ] while the band at 2922 cm −1 is assigned to the asymmetric stretching mode of the -CH 2 - group [ 39 , 40 ]. The corresponding symmetric stretching vibrations are found at 2870 cm −1 for the methyl group and at 2845 cm −1 for the methylene group [ 37 , 39 , 40 ]. The ratio between the intensity of the aliphatic over aromatic C-H stretching modes bands is higher for the ABT02 with respect to ABT01, which could be an indication of a more crosslinked network.…”

“…In the region around 40–35 ppm the signals associated with -CH 2 Br can also be found [ 44 ]. Carbons associated with methyl groups are found around 17 and 12 ppm [ 37 , 43 ]. It is interesting to observe the presence of these functional groups since they are not present in either the monomer or crosslinker.…”

Silica Monolith for the Removal of Pollutants from Gas and Aqueous Phases

“…The toluene adsorption properties of different porous silicas (i.e., fumed silica, SBA-15 and commercial MCM-41) have been recently reported by our group [ 16 ] and we have shown that the porous architecture of different silicas have an important effect on the final adsorption properties. In the same conditions, we also tested the adsorption behaviour of siliceous zeolites and hypercross-linked polymers [ 17 ]. We derived that whereas siliceous zeolite adsorbs 21 Q% of toluene, HyperCross-linked Polymers (HCP S ) with flexible structures are able to adsorb more than 140 Q% of toluene.…”