Applications of zirconium-based metal-organic frameworks for fluorescent sensors

Metal-organic frameworks (MOFs) are considered ideal candidates for sensing materials due to their rich func-tional groups, high specific surface area, elaborate pore structure and flexible framework designability. In particular, zirconium-based MOFs (Zr-MOFs) have attracted considerable attention for their robust skeleton and excellent stability, and the application of Zr-MOFs as fluorescent sensors has been widely explored. In this re-view, the recent key advances in fluorescent sensing materials based on Zr-MOFs were summarized, including the synthesis strategy, detection mechanism, and design principle. We classified these sensors into three categories based on ligand structure to investigate their design principles: 1) linear ligands, represented by UiO-66, with diverse isoreticular structure; 2) tetracarboxylic acid ligands, represented by PCN-224, most of which are functional heterocyclic ligands; 3) tricarboxylic acid ligands, represented by MOF-808 and 2D Zr-BTB, which is a suitable carrier for luminescent guest. Then, a summary of the applications of Zr-MOFs fluorescent sensors for the detection of metal cations, anions, pH, gases, explosives, biomolecules, and drugs were presented. Finally, we also illustrate the problems and challenges that urgently need to be overcome in order to design Zr-MOFs for fluorescent sensors.