Thiazole-Decorated PCN-700 Metal–Organic Frameworks for Diclofenac Luminescence Sensing and Adsorption in Wastewater
Giacomo Provinciali, Agostina Lina Capodilupo, Anna Mauri, Simona Galli, Lorenzo Donà, Bartolomeo Civalleri, Giulia Tuci, Giuliano Giambastiani, Clara Piccirillo, Andrea Rossin
Abstract
The defective sites on the eight-connected [Zr 6 O 4 (OH) 8 (H 2 O) 4 ] 8+ nodes of the metal–organic framework (MOF) PCN-700 are the anchoring points for its postsynthetic decoration with extra linkers via solvent-assisted linker incorporation (SALI). The thiazolo[5,4- d ]thiazole-2,5-dicarboxylic acid ( H 2 TTz ) and the newly prepared 2,2′-(1,4-phenylene)bis(4-methylthiazole-5-carboxylic acid) ( H 2 TzPhTz Me ) have been inserted into PCN-700 to obtain the mixed-linker MOFs (MIXMOFs) [ TTz @PCN-700] ( 1 ) and [ TzPhTz Me @PCN-700] ( 2 ). The two MIXMOFs are luminescent, and they have been exploited as sensors and adsorbents of diclofenac sodium (DCF) in aqueous solutions at ambient temperature. The emission intensity of 2 shows an unprecedented “parabolic” trend combined with a (λ max ) em blue shift from 470 to 430 nm that induces a color change from turquoise to blue in the presence of DCF upon irradiation with a suitable wavelength. Its DCF limit of detection is 8.4 × 10 –6 M. 1 is an excellent DCF “sponge” in water, with a maximum adsorption capacity ( X m ) of 263.2 mg/g. Density functional theory (DFT) modeling of the electronic structure of the empty and DCF-loaded MOFs has revealed that the highest-occupied crystal orbital (HOCO) is mainly centered on Me 2 -BPDC 2– in 1, while it is prevalently centered on TzPhTz Me(2−) in 2 . This may be at the origin of the different emission behavior of the two MOFs.