Ultra-low limit of luminescent detection of gossypol by terbium(III)-based metal-organic framework

The widespread use of gossypol-containing animal feed and cottonseed oil poses a great threat to water quality and livestock and human health, and there is an urgent need for a sensor for the rapid detection of trace amounts of gossypol in aqueous solutions and cottonseed oil. As a result, an unprecedented three-dimensional metal-organic framework sensor based on terbium(III) and a flexible ligand 4-(3,5-dicarboxyphenoxy)isophthalic acid (H4L) was developed. Tb-MOF, {[Tb(H2O)(HL)]·0.5MeCN·0.25 H2O}n, is highly stable in water and polar organic solvents and exhibits terbium-centered luminescence with 44% quantum yield. Suspensions of MOF in water and ethanol demonstrate a luminescence quenching response to cotton phytotoxicant gossypol with an unprecedented low detection limit of 0.76 nM and 1.89 nM, correspondingly, without interference from the components of cottonseed oil and blood plasma, making it suitable for the detection and determination of gossypol in real-life water and oil samples. Significantly, Tb-MOF is the first highly efficient sensor that uses water as a solvent to detect trace amounts of gossypol, and it can visualize and quantify gossypol in edible-grade cottonseed oil as well, which proves its great potential for practical application. In addition, Tb-MOF exhibited a detection limit for Fe3+ (0.23 μM) among the lowest reported for lanthanide-based MOFs in aqueous solutions so far.