Ni–Pd bimetallic nanoparticle stabilized polymer membrane as an efficient dip-catalyst for oxidative coupling of aromatic amines to access symmetrical and unsymmetrical azo compounds

Abstract

The azo linkage is an important chemical motif with wide applications in the pharmaceutical, agrochemical, textile, paint, and food industries. The development of effective dip-catalysts that would convert aromatic amines to symmetric or asymmetric azobenzenes in the presence of aerobic molecular oxygen under mild conditions is really challenging. Here, we have developed a dip-catalyst by immobilizing poly(vinylpyrrolidone)(PVP) stabilized Ni–Pd bimetallic nanoparticles on a nylon-6 membrane through UV-crosslinking for performing such reactions. The catalyst was highly efficient for the oxidative coupling of aromatic amines to the corresponding aromatic azo compounds under aerobic conditions without employing hazardous substances or ecologically harmful nitrites. Notable reaction features include a broad substrate range (aromatic, heterocyclic, and polyaromatic amines), a high yield (∼98%), low catalyst loading, and a simple work-up method. The dip-catalyst exhibits exceptional reusability for multiple catalytic cycles while retaining its high performance and structural characteristics. The gram-scale synthesis of high-value compounds like azobenzene provided additional evidence of the practical utility of the proposed catalyst.