Pd NPs encapsulated by COF in nitrogen-doped macroporous chitosan carbon microspheres act as an efficient and recyclable multifunctional catalyst

Developing efficient, recoverable, and versatile palladium catalysts is of great significance. In this paper, nitrogen-doped macroporous chitosan carbon microspheres (MCM) were prepared by emulsion polymerization method with polystyrene microspheres as a template. The core-shell structured MCM@Pd@COF catalysts were then prepared using a coral-structured COF shell layer to seal the Pd NPs in the channels of the MCM. The introduction of COF with good photocatalytic properties improved the stability of the material while imparting its photocatalytic properties without affecting its catalytic activity. MCM@Pd@COF efficiently catalyzed the Suzuki coupling reaction (Iodobenzene and phenylboronic acid, 98 % yield, TON = 6.7 x 105, TOF = 3.4 x 105 h-1), and the reduction of 4-nitrophenol (4-NP, reaction rate constant Kapp = 9.48 x 10-1 min-1). The kinetic study revealed that the reduction reaction of 4-NP by MCM@Pd@COF was compliant with the quasi-first-order kinetic model. Furthermore, MCM@Pd@COF removed up to 96.3 % of high concentrations of rhodamine B (RhB) within 30 min under visible light irradiation. Mechanistic investigation showed that MCM@Pd@COF efficiently promotes the production of center dot O2 - and center dot OH radicals under visible light irradiation, which drives the photocatalytic degradation of organic dyes. There was no significant decrease in the catalytic activity of MCM@Pd@COF over the eight uses.

Automated summary

Developing efficient and recoverable palladium catalysts is important. In this study, nitrogen-doped macroporous chitosan carbon microspheres (MCM) were prepared using emulsion polymerization, and core-shell structured MCM@Pd@COF catalysts were developed. These catalysts efficiently catalyzed Suzuki coupling reactions and the reduction of 4-nitrophenol, and showed high stability and photocatalytic properties under visible light irradiation. Mechanistic investigation revealed the efficient production of radical species under visible light, driving the photocatalytic degradation of organic dyes. The catalytic activity of MCM@Pd@COF remained unchanged after multiple uses.