A novel supramolecular polymer π-gel based on bis-naphthalimide functionalized-pillar[5]arene for fluorescence detection and separation of aromatic acid isomers

A novel supramolecular polymer monomer based on bis-naphthalimide functionalized-pillar[5]arene (BPN) was designed and synthesized. The naphthalimide moiety on BPN offers a π-π stacking site, a hydrogen bonding site and a fluorophore functional group. Pillar[5]arene groups also act as precursors for π-π interactions and guest molecule binding sites. The BPN could self-assemble into a stable supramolecular polymer π-gel (BPN-G) through an effective cooperative interaction between naphthalimide moieties and pillar[5]arene groups. Interestingly, the as-produced supramolecular polymer π-gel BPN-G showed impressive selectivity and sensitivity toward o-hydroxybenzoic acid, o-aminobenzoic acid and p-nitrobenzoic acid and their isomers, as well as other common organic acids. Moreover, the xerogel of BPN-G could efficiently adsorb and separate p-NBA from water at a separation rate of 93.2%. The supramolecular polymer π-gel BPN-G has potential application in the detection and separation of aromatic acid isomers.