Construction of a novel coordination polymer for selective fluorescence recognition and efficient adsorption of tryptophan in aqueous solution

Abstract

The efficient separation and purification of L-tryptophan (L-Trp) from fermentation broth are essential for reducing production costs. Here, we report a new 1,1́-binaphthyl-based copper coordination polymer (R-Cu CP) that enables selective fluorescence recognition and efficient adsorption of L-Trp from aqueous solutions. A three-dimensional (3D) CP with a suitable cavity size (17 × 8 Å) was constructed by coordinating copper ions with the dicarboxylate ligand (R)-H3L derived from 1,1́-binaphthyl phosphoric acid. The prepared R-Cu CP exhibits extraordinary adsorption of L-Trp, up to 1055 mg/g. The specific fluorescence quenching response to L-Trp can be achieved by the ultrasonic exfoliation of two-dimensional (2D) CP nanosheets (CPNs). X-ray photoelectron spectroscopy and density functional theory calculations revealed that the efficient adsorption of L-Trp by R-Cu CP is due to the synergistic effect of coordination interactions, hydrogen bonding interactions, electrostatic interactions, and host–guest interactions, and the quenching mechanism is attributed to the photoinduced electron transfer from L-Trp to R-Cu CP and the competitive absorption of excitation energy by L-Trp.