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<p>To address the critical need to improve metal-support interactions and prevent palladium agglomeration in heterogeneous catalysis, this study reports a novel strategy for designing graphene oxide frameworks (GOFs) using tridentate organic linkers with varying heteroatom densities. Two palladium-functionalized nanocatalysts, Pd@GOF1 and Pd@GOF2, were successfully synthesized by cross-linking graphene oxide (GO) via amide formation with 1,3,5-tris(4-aminophenyl)benzene, and per-hydroxylated GO via esterification with nitrogen-rich 4,4′,4′′-s-triazine-1,3,5-triyltri-p-aminobenzoic acid, respectively. FT-IR analysis confirmed the successful framework assembly and the formation of N–Pd coordination bonds (at ~ 530&#xa0;cm⁻¹). Notably, Atomic Absorption Spectrometry (AAS) demonstrated that the nitrogen-dense triazine linker in GOF2 led to a significantly higher palladium loading of 31.92 wt% compared to only 0.532 wt% for the benzene-linked GOF1. XRD and TEM analyses revealed highly dispersed palladium nanoparticles with average sizes of 2.08&#xa0;nm for Pd@GOF1 and 4.68&#xa0;nm for Pd@GOF2. Despite this exceptionally high metal density in Pd@GOF2, the nitrogen-rich framework effectively stabilizes and maintains the palladium nanoparticles within ultra-small nanometric dimensions, successfully suppressing severe macro-agglomeration. In the Heck-Mizoroki cross-coupling of bromobenzene and styrene in an eco-friendly H₂O/EtOH solvent, Pd@GOF2 exhibited exceptional activity, achieving a 98% yield within just 5&#xa0;min with a remarkable turnover frequency (TOF) of 39.2&#xa0;h⁻¹, whereas Pd@GOF1 required 2&#xa0;h to reach the same yield (TOF = 9.5&#xa0;h⁻¹). Furthermore, both heterogeneous catalysts demonstrated robust structural stability, maintaining high yields (up to 92% for Pd@GOF2) after five consecutive recycling cycles without significant metal leaching. This work highlights the pivotal role of rational heteroatom functionalization in creating highly efficient, stable “nanoreactors” for C-C coupling reactions.</p>

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Comparative evaluation of benzene vs. nitrogen-rich triazine linker in Pd@Graphene organic frameworks for enhanced Heck-Mizoroki reaction

  • 期刊论文

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  • 发表日期：

    2026年7月13日

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  • Arezoo Shekarizadeh,
  • Roya Azadi,
  • Elham Sohrabifard,
  • Roya Mirzajani

摘要

To address the critical need to improve metal-support interactions and prevent palladium agglomeration in heterogeneous catalysis, this study reports a novel strategy for designing graphene oxide frameworks (GOFs) using tridentate organic linkers with varying heteroatom densities. Two palladium-functionalized nanocatalysts, Pd@GOF1 and Pd@GOF2, were successfully synthesized by cross-linking graphene oxide (GO) via amide formation with 1,3,5-tris(4-aminophenyl)benzene, and per-hydroxylated GO via esterification with nitrogen-rich 4,4′,4′′-s-triazine-1,3,5-triyltri-p-aminobenzoic acid, respectively. FT-IR analysis confirmed the successful framework assembly and the formation of N–Pd coordination bonds (at ~ 530 cm⁻¹). Notably, Atomic Absorption Spectrometry (AAS) demonstrated that the nitrogen-dense triazine linker in GOF2 led to a significantly higher palladium loading of 31.92 wt% compared to only 0.532 wt% for the benzene-linked GOF1. XRD and TEM analyses revealed highly dispersed palladium nanoparticles with average sizes of 2.08 nm for Pd@GOF1 and 4.68 nm for Pd@GOF2. Despite this exceptionally high metal density in Pd@GOF2, the nitrogen-rich framework effectively stabilizes and maintains the palladium nanoparticles within ultra-small nanometric dimensions, successfully suppressing severe macro-agglomeration. In the Heck-Mizoroki cross-coupling of bromobenzene and styrene in an eco-friendly H₂O/EtOH solvent, Pd@GOF2 exhibited exceptional activity, achieving a 98% yield within just 5 min with a remarkable turnover frequency (TOF) of 39.2 h⁻¹, whereas Pd@GOF1 required 2 h to reach the same yield (TOF = 9.5 h⁻¹). Furthermore, both heterogeneous catalysts demonstrated robust structural stability, maintaining high yields (up to 92% for Pd@GOF2) after five consecutive recycling cycles without significant metal leaching. This work highlights the pivotal role of rational heteroatom functionalization in creating highly efficient, stable “nanoreactors” for C-C coupling reactions.