Biomimetic enzyme MOF-NADH-mediated and 3,3',5,5'-tetramethylbenzidine-based colorimetric assay for formaldehyde detection

This work reported a new MOF-NADH-mediated colorimetric assay for highly sensitive detection of FA based on the biomimetic enzyme reductive reaction and the co-catalysis of metalloporphyrin with oxidized 3,3′,5,5′-tetramethylbenzidine (oxTMB) as the color indicator in the sensing process. An excellent linear relationship (R 2 = 0.9958) was obtained by a broad signal fitting dynamic range of FA (1 μ M-25 mM), and the detection limit of the MOF-NADH for FA was 4.5 μ M. Specific experiment was also carried out to confirm the selectivity of MOFzyme-NADH system to FA. To realize smart sensing of FA, a test paper strip-based sensor with a portable smartphone sensing platform had been developed to process the RGB values by a color-read APP. Furthermore, the paper strip-based sensor with the smartphone platform had been employed for the practical detection of FA in real samples from environment and food, and series of good results were obtained. • A new colorimetric assay for FA detection based on the biomimetic MOF-NADH has been developed. • Ag + /MOF-NADH‑triggered redox interconversion of TMB(colorless) and oxTMB (bule) served as intuitive color indicator. • A highly sensitivity and selectivity toward FA was obtained (detection limit: 4.5 μ M). • A paper strip-based sensor with the smartphone platform had been employed for the detection of FA in real samples.