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 (R2 = 0.9958) was obtained by a broad signal fitting dynamic range of FA (1 μM-25 mM), and the detection limit of the MOF-NADH for FA was 4.5 μM. 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 μM).•A paper strip-based sensor with the smartphone platform had been employed for the detection of FA in real samples.