Post-modification synthesis of functionalized Zr-based metal-organic framework/alginate aerogel for sensitive fluorescence sensing and efficient adsorption removal of Cu(II) and Cr(VI) in apple juice.

Heavy metal pollution in food, particularly Cu(II) and Cr(VI), poses a significant threat to human health. A bifunctional composite aerogel (MDS) is successfully synthesized, immobilizing a 5,5'-diamino-2,2'-bipyridine (dabpy) post-modified MOF-808 within a sodium alginate (SA) aerogel for sensitive detection and efficient removal of heavy metal ions in apple juice. Mechanism studies reveal that pyridinic N and NH2 in MDS display a high affinity for Cu(II), while Cr(VI) exhibits an electrostatic attraction to the protonated NH2. The interaction process triggers electron transfer, which leads to fluorescence quenching. MDS aerogel shows detection of Cu(II) and Cr(VI) with low limits of detection, and adsorption capacities of 354.91 mg/g for Cu(II) and 258.62 mg/g for Cr(VI). The MDS aerogel removal efficiency exceeded 94% in apple juice. In vitro cytotoxicity assays indicate low cytotoxicity of MDS. This work offers a potential bifunctional platform for heavy-metal sensing and removal in food matrices.