A Novel Rotaxane@MOF\nas Multiresponsive Fluorescence\nSensor for Detecting Fe<sup>3+</sup>, Cr<sub>2</sub>O<sub>7</sub><sup>2–</sup>, and Antibiotics

The first example rotaxane@MOF (named as <b>CUST-761</b>)\nhas been designed and constructed via combining CB[6]-based rotaxane\n([PR44]<sup>2+</sup>·2[NO<sub>3</sub>]<sup>−</sup>), 4,4′-biphenyldicarboxylate\nsodium salts (Na<sub>2</sub>BPDC), and transition metal cadmium ion\nunder solvothermal conditions. X-ray single crystal diffraction revealed <b>CUST-761</b> exhibits a two-dimensional (2D) layered structure\nwhere rotaxanes are well embedded in the crystal lattices formed by\nBPDCs and cadmium ions. Thermogravimetric analysis (TGA) and Powder\nX-ray diffraction (PXRD) showed that <b>CUST-761</b> possesses\nexcellent stability. The utility of <b>CUST-761</b> as fluorescence\nsensors has also been discussed. The results indicated that <b>CUST-761</b> can be used as a multiresponsive fluorescence sensor\nfor detecting Fe<sup>3+</sup> and Cr<sub>2</sub>O<sub>7</sub><sup>2–</sup> with good sensitivity, high selectivity, and recoverability,\neven in the presence of other interfering ions. Besides, <b>CUST-761</b> also can selectively detect nitrofurantoin. The mechanism of <b>CUST-761</b> as a multiresponsive fluorescence sensor for detecting\nFe<sup>3+</sup>, Cr<sub>2</sub>O<sub>7</sub><sup>2–</sup>,\nand the antibiotic nitrofurantoin has been clarified by experiments\nand theoretical calculations. This work provides insights into the\ndesign and synthesis of fluorescence sensing crystal-state materials.