Construction and application of MgAl LDH-Schiff base-supported palladium nanocatalyst for Heck reactions and reduction of organic pollutants
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In this study, a novel nanostructured Pd NPs@MgAl LDH-Schiff base-supported catalyst system was developed through a deposition of Pd NPs on the modified MgAl-layered double hydroxide (MgAl LDH). Structural/morphological features of Pd NPs@MgAl LDH-Schiff base nanocatalyst were investigated by XRD, FESEM, BET, FTIR, EDS, and TEM analyses. It was found that Pd NPs with an average particle size of about 14.50 ± 1.24 nm were successfully produced without agglomeration. The catalytic performance of the prepared Pd NPs@MgAl LDH-Schiff base as a heterogeneous nanocatalyst was subsequently tested in both Heck reaction (HCR) and reductions of 4-nitrophenole (4-NP) and 2-nitroaniline (2-NA). The tests revealed that Pd NPs@MgAl LDH-Schiff base nanocatalyst effectively coupled HCR of styrene and different aryl iodides/bromides by producing reaction yields between 90 and 98% for 3–5 h. In addition, Pd NPs@MgAl LDH-Schiff base nanocatalyst confirmed that it had significant catalytic power by converting 4-NP and 2-NA to 4-aminophenole (4-AP) and 2-phenylenediamine (2-PDA) in 50 s and 45 s, respectively. The rate constants for the reductions of 4-NP and 2-NA in the presence of Pd NPs@MgAl LDH-Schiff base nanocatalyst were determined as 0.017 s−1 and 0.023 s−1, respectively. Due to its heterogeneous nature and the strong synergistic interaction between Pd NPs and prepared MgAl LDH-Schiff base as support, Pd NPs@MgAl LDH-Schiff base nanocatalyst was easily recovered and reapplied for six consecutive runs with unchanged structural/morphological features.