A novel magnetic N-rich covalent triazine framework-copper(ii) complex as an efficient nanocatalyst for Ullmann...

In the present work, we describe the development of a new nitrogen-rich polymer grafted onto hercynite magnetic nanoparticles (MNPs) for the stabilization of a copper catalyst. In this approach, the surface hydroxyl groups of hercynite were covalently bonded to cyanuric chloride, which was subsequently polymerized with melamine to generate a nitrogen-rich covalent triazine polymer network around the hercynite surface. This framework was then coordinated with copper to yield a new heterogeneous nanomagnetic copper catalyst. The as-prepared [hercynite@TCOP-Cu(ii)] was applied in Ullmann C-O coupling of various aryl halides with phenolic substrates using PEG-400 as an environmentally benign reaction medium, furnishing the corresponding diaryl ethers in good to excellent yields with high selectivity and short reaction times. Furthermore, the use of aniline and mercaptophenol provided the corresponding diarylamines and diaryl sulfides in excellent yields, confirming the generality and broad substrate scope of this methodology, as well as its efficiency in C-N and C-S cross-coupling reactions in addition to C-O couplings. The catalytic system exhibited a heterogeneous nature, excellent stability, and reusability over at least six consecutive recovery cycles via magnetic separation with minimal loss of activity. These findings highlight the potential of this nanocomposite as a practical, sustainable, and highly efficient catalyst for Ullmann-type coupling reactions.