Synthesis of novel coordination polymer Cd-MOF and fluorescence recognition of tryptophan

•High fluorescence recognition of tryptophan (Trp) by Cd-MOF synthesized by solvothermal method.•The prepared fluorescent sensor detects the detection of Trp with a wide linear range and low detection limit.•The sensor has been successfully applied to the determination of Trp in actual milk samples. The coordination polymer Cd-MOF with three-dimensional network structure was successfully synthesized by conventional solvothermal method, which possesses excellent chemical and structural stability. Among the 20 amino acids, only tryptophan (Trp) showed a significant fluorescence enhancement effect on Cd-MOF, which was attributed to the large overlap between the UV absorption peak of tryptophan and the fluorescence excitation spectrum of Cd-MOF, indicating that the UV absorption of them is competitive, which enhanced the UV absorption of Cd-MOF and thus enhanced the luminescence intensity simultaneously. The Cd-MOF was further found to have a low detection limit of 1.7µM, a relatively wide linear range (0-100µM) and a stable response time for the recognition of tryptophan, as well as a good resistance to the interference of other amino acids. The method has been successfully applied to the spiked recovery determination of tryptophan in milk with the recoveries of 99.6%-101% and RSD≤1.50%. Therefore, this work demonstrated that Cd-MOF can be used as a fluorescent probe for the selective detection of tryptophan, and also may provide new opportunities for the rational design of future tryptophan fluorescent probes.