High-nitrogen containing covalent triazine frameworks as basic catalytic support for the Cu-catalyzed Henry reaction

Abstract

Functionalization of porous organic frameworks by a rational design of the monomer allows to prepare tailor-made materials. The use of nitrogen-based polydentate building blocks provides specific and versatile functional groups to allow a robust binding site and/or ligand for metal complexes. In this regard, a rigid and planar tris-bidentate ligand-based 5,6,11,12,17,18-hexaazatrinaphthylene (HATN) ligand was employed for the preparation of highly porous and stable Covalent Triazine Frameworks (CTFs). The resulting HATN-based CTF exhibits a remarkably high BET surface area of 1684 m2/g and a total pore volume of 0.79 cm3/g. After post-synthetic metalation with a Cu(OAc)2 complex, it can be utilized as an efficient heterogeneous catalyst for the Henry reaction of aromatic aldehydes and nitromethane under mild reaction conditions. The Cu@HATN-CTF catalyst exhibit an excellent catalytic performance and a higher TON than the conventional Cu-based porous materials. This is probably due to the geometry and the electronic configuration effect, as the paddlewheel structure of the complex is broken upon grafting onto the HATN-CTF.