Highly dispersed Pd nanoclusters supported on covalent triazine-based frameworks for highly efficient aryl nitro reduction and Ullmann coupling

Abstract

The feasible preparation of Pd catalysts, one of the most widely used catalysts, with high performance and easy recovery still remains the greatest challenge. Covalent triazine-based frameworks (CTFs), by virtue of strong covalent linkages and abundant nitrogen atoms, have been deemed as a central subclass of porous supports for nano-functional materials including metal nanocatalysts. Herein, a series of CTFs have been prepared by ionothermal synthesis followed by rearrangement at higher temperatures (500–900 °C). The CTF-immobilized nano-Pd(0) catalysts with different particle size distributions (<0.5, 1.35 ± 0.93, 2.21 ± 1.43, 3.80 ± 1.33, 6.10 ± 3.23 nm) were then prepared by simply suspension impregnation-in-situ reduction. Among them, the smallest and highly dispersed Pd nanoclusters (Pd/CTF-600) exhibited excellent activity and outstanding recyclability in aryl nitro reduction and Ullmann coupling. The study provides a new insight for the preparation of high-performance metal nano-catalysts that could enable efficient chemical transformations.