Post synthetic modification of Zr-MOF with phenylboronic acid: Fluorescence sensing of sialic acid

Luminescent metal-organic frameworks (LMOFs) have become an important class of fluorescence sensing materials, whereas direct applications of LMOFs for identifying analytes still remain a challenge. Post synthetic modification (PSM) is an effective strategy to improve the performance of LMOFs. In this work, PSM of UiO-66NH2 was achieved with 4-carboxyphenylboronic (4-CPBA), based on which a fluorescence sensor, UiO-CPBA, was designed. The sensor was synthesized in the off state utilizing the photo-induced electron transfer (PET) process caused by the introduction of 4-CPBA and applied to the recognition of sialic acid (SA). The interaction between the boric acid group and the triol side chain of SA interrupted the PET process and turned on the fluorescence, thus fluorescence detection of SA was realized. This method exhibited a linear range of 1-100 mu M and a limit of detection (LOD) of 0.15 mu M for SA determination. The analysis of human serum verified the practicability of UiO-CPBA for SA, giving a new way for the construction of SA sensing platforms toward complex real samples.