Phase-selective gelators based on benzene 1,3,5-tricarboxamide for aromatic solvents recovery and dye removal

Three supramolecular gelators (2a, 3a, 3b) of a benzene 1,3,5-tricarboxamide (BTA) motif were synthesized and studied for their gelation behavior. 3a and 3b were designed and synthesized for the first time. 3a showed excellent gelation behavior in a variety of aromatic solvents with minimum gel concentration in the range of 0.7% (w/v)–2.1% (w/v). The morphology of the stable gels indicated the formation of a highly entangled fiber network in mesitylene and xylene. FT-IR studies revealed an evident role of intermolecular hydrogen bonding in the self-assembly process. UV studies showed that π–π interaction is the driving force for the gelator to form a gel. The experiment results of the aromatic solvents recovery showed that the BTA-based gelator with naphthyl group exhibits excellent phase selectivity on gel mesitylene and xylene from a mixture of aromatic solvent and water when applied in the powder form at 3.2% (w/v) in mesitylene and 4.2% (w/v) in xylene. π-π stacking between phenyl groups and naphthyl groups of gelator might provide an additional driving force for the formation of a dense three-dimensional network capable of phase-selective gelation of aromatic solvents from a mixture of aromatic solvent and water. The experiment results of the dye removal indicated that the entangled fibrous network and the rheological property enable the BTA-based phase-selective gelator to be used as recyclable materials for removing toxic dyes from a mixed solution of water and organics with efficiency as high as 99.5%. And 3a can gel crude oil from a mixture of water and oil by using crude oil as carrier solvents. Thus, these smart systems possess the potential to be used effectively in water purification and oil spills remediation.