Defective porphyrin Zr metal–organic framework cube decorated with platinum: Synthesization and application for colorimetry/smartphone sensing of tetracycline

Noble metal-based oxidase-like (MOD) nanozymes show great applications referring to the common peroxidase-like (POD) nanozymes, while their insufficient activity and stability need to be addressed urgently. Herein, by introducing defective porphyrin Zr metal–organic framework (PCN-224) cube as metal carrier and in-situ growth method, a novel MOD nanozyme of defective PCN-224 decorated with platinum nanoparticles (PCN-224@Pt NPs) was prepared and characterized firstly, which possesses extremely high loading amount of Pt (72.82 wt%) and prominent catalytical activity (K m , 0.18 mM; V max , 10 −8 M s −1 ). In addition, based on the specifical bonding of PCN-224 towards antibiotic tetracycline (TC), we revealed that TC could inhibit the catalytical activity of PCN-224@Pt NPs nanozyme, and then a sensitive colorimetric sensing platform was thus designed to detect TC, which could effectively avoid the utilization of H₂O₂ coupled with superior analytical performances compared to the reported POD nanozyme-based sensing platforms. Meanwhile, by integrating this nanozyme to medical cotton swab and coupling with the help of smartphone, simple, low-cost and onsite analysis for TC could be achieved successfully. This work not only proposed an innovative way via defect engineering to design MOD nanozymes with excellent catalytical activity, but also developed a highly effective colorimetric and smartphone dual-mode sensing method for TC, thus showing great potential applications.