Multi-enzyme simulation activity of MXene-based metal composites and the application for detection and degradation of phenolic pollutants

Phenolic pollutants are commonly employed in industries such as petrochemicals, dyeing, textiles, and pesticides, which cause great harm to our living environment and food safety. In this paper, the MXenes-based metal composites (M/MXenes, M = Cu, Co, Ni, Zn, Fe, Mn) with multi-enzyme mimic activity were prepared by a facile molten salt method. The M/MXenes have mimic catalytic activity of peroxidase (POD), ascorbic acid oxidase (AAO), catalase (CAT), superoxide dismutase (SOD) and laccase. The catalytic properties of M/MXenes were analyzed and discussed in detail. In addition, M/MXenes still have excellent catalytic performance and stability in harsh pH and high temperature environments, making them very suitable for practical applications. Due to the excellent laccase mimic activity of M/MXenes, a simple colorimetric sensor was constructed for the detection and degradation of phenolic pollutants. Because obvious color changes can be observed during the catalytic process of phenolic pollutants by M/MXenes, M/MXenes were fixed into sodium alginate (SA) to form a simple hydrogel-based sensing platform for 2, 4-chlorophenol, methoxyphenol, 4-bromophenol, 3-bromo-4-methoxyphenol, 3-bromo-4-methylphenol, hydroquinone and 1,8-naphthol. By introducing different concentrations of phenolic compounds, a series of color changes on the gel carrier can be observed by naked eyes. Then, the red (R), green (G) and blue (B) values matching with the color change of the hydrogel were read out by the color recognition application in the smartphone, and the RGB value was converted into the concentration of phenolic compounds, which offered a convenient and reliable method for the rapid detection of phenolic compounds. Thus, the strategy offers the potential in rational design of nanozymes with the advantages of multi-enzyme mimic activity, simple preparation, low cost and good stability.