Sustainable recycling of polyamides via C-N bond cleavage facilitated by methyl tosylate under mild conditions.

Abstract

The escalating issue of plastic "white pollution" urgently calls for efficient and sustainable recycling strategies. Herein, we propose an approach for the depolymerization of polyamides via alcoholysis, utilizing methyl tosylate as an activator to cleave robust amide C-N bonds under mild reaction conditions. This strategy facilitates the efficient conversion of diverse polyamides into high-value monomers, such as ε-caprolactam, amino acid esters, or diamines/diesters, with nearly quantitative yields and excellent selectivities. Experimental and theoretical mechanistic investigations reveal that p-toluene sulfonic acid plays a crucial role in the efficient alcoholysis of polyamides, mediating the formation of a tetrahedral intermediate through the nucleophilic attack of alcohol on the amide group. This protocol not only demonstrates exceptional applicability to complex waste plastic mixtures containing polyamides but also highlights its potential for scalable implementation, offering a practical and sustainable recycling approach for more effective management of white pollution.