In-situ ultrasonic synthesis of Palladium nanorods into mesoporous channel of SBA-15 and its enhanced catalytic activity for Suzuki coupling reaction

Abstract Palladium nanorods (PdNRs) into mesoporous channels of SBA-15 nanocatalyst (PdNRs/SBA-15) were synthesized by a green and surfactant-free ultrasonic method without any surfactants and complex chemical modification and chemical method in absence of ultrasound, respectively. The PdNRs/SBA-15 catalysts were characterized by XRD, TEM, XPS, N 2 absorption-desorption and FT-IR analysis. The results showed that PdNRs with 15.96 ± 3.89 nm long and 5.69 nm wide were highly dispersed into mesoporous channels exploiting the confine effect of SBA-15 pore channel, while reunited PdNPs were distributed on the outside surface of SBA-15 in PdNPS/SBA-15 prepared by chemical method. The in-situ ultrasonic reduction of PdNRs/SBA-15 by the reductive radical (induced by ultrasonic process) was good for higher dispersion of Pd species and the formation of Pd species inside the mesoporous channel of SBA-15 without any structure-directing agents or surfactants. The yield of Suzuki coupling reaction between 4-bromotoluene and phenylboronic acid catalyzed by PdNRs (5)/SBA-15 reached 96.4%, which was much higher than that of PdNPs(5)/SBA-15 prepared without ultrasound (76.3%). PdNRs (5)/SBA-15 could be reused up to five times without a significant activity loss due to the strong chemical interaction and the unblocked channel.