No abstract

No abstract

No abstract

The application of porphyrin metal−organic frameworks (MOFs) as a ratiometric electrochemical sensing platform is still unexplored. In this paper, we report a ratiometric electrochemical sensor by the integration of multiple redox centers into porphyrin MOFs for the detection of dissolved oxygen (DO). Specifically, the ferrocene (Fc) group was integrated into the nanosized PCN-222(Fe) (PCN = porous coordination networks) via acid−base reaction to synthesize the Fc@PCN-222(Fe) composite with two redox centers of the Fc group and Fe-porphyrin. The Fc group that is insensitive to DO serves as an internal reference, and the Feporphyrin in PCN-222(Fe) is a DO indicator. The ratios of the cathodic currents for the two redox centers exhibit a linear relationship with DO concentrations from 2.8 to 28.9 mg mL −1 and a limit of detection of 0.3 mg mL −1 . In addition, the ratiometric electrochemical sensor has high selectivity and stability for DO sensing results from the Fc@PCN-222(Fe) composite. Because there are numerous redox centers, such as methylene blue and thionine, which can be integrated into MOFs, many MOF-based ratiometric electrochemical sensors can be simply developed for high-performance biosensing.

Exploitation of metal–organic aerogels (MOAs) with porous properties for the immobilization of enzymes should have significant applications. A facile method for the synthesis of MOAs using poly­(propylene glycol) (PPG) as a gelling agent is presented in this paper. In particular, a porous UiO-66-NH2 aerogel containing an iron porphyrin unit has been synthesized using PPG. The MOA not only displays high mesopores for glucose oxidase (GOx) immobilization but also has the unit of iron porphyrin as a peroxidase mimick for a cascade reaction. After the immobilization of GOx, the composite was used for the colorimetric sensing of glucose, exhibiting a good linear range, a low limit of detection, and excellent selectivity. Furthermore, the MOA-immobilized GOx shows enhanced stability against organic solutions and longer storage stability at room temperature, attributed to the protective effect of the UiO-66-NH2 aerogel. This MOA with porous properties should provide an extended platform for enzyme immobilization and open up a route for the development of biocatalyst systems for advanced applications in biosensing, bioindustrial catalysis, and biofuel cells.