Triazole-functionalized hydrochar-stabilized Pd nanocatalyst for ullmann coupling

• Published in: Chemosphere (Oxford) 2022-12, Vol.308, p.136250-136250, Article 136250
• Main Authors: Pereira, Guilherme Ramos, Lopes, Renata Pereira, Wang, Wenjuan, Guimarães, Tiago, Teixeira, Robson Ricardo, Astruc, Didier
• Format: Article
• Language: English
• Subjects: Biomass; Biphenyl; Catalyst support; Click reaction; Green chemistry; Sustainability
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/j.chemosphere.2022.136250

Biomass valorization is essential, particularly in emerging countries. Here, hydrochar from arabica coffee straw was functionalized with a triazole group (HD-TRz) for use as a support of palladium nanoparticles (PdNPs-HD-TRz) applied in the Ullmann coupling reaction for the first time. It provided remarkably excellent selectivities, conversions at a temperature as low as 45 °C and catalyst recyclability, surpassing previous literature performances. Hydrochar was obtained by one-pot reaction via hydrothermal synthesis, using NaOH solution as activating agent and functionalized with a 1,3-triazole group by CuAAC “click” reaction. The PdNPs were prepared via reduction of hydrochar-bound Pd(II) using NaBH4. Hydrochar functionalization was monitored by infrared spectroscopy, and X-ray diffraction (XRD) allowed to observe carbon and palladium planes in hydrochar and PdNPs HD-TRz structures. The PdNPs presented a spherical shape with 2.1 ± 0.1 nm size, homogeneously distributed in the carbon coverslips. The HD-TRz-supported PdNPs were used as a catalyst in the Ullmann reaction of iodobenzene, using ethanol as solvent with 100% of conversion and 91% selectivity at 45 °C. The material was reused, presenting 100% of conversion and selectivities of 92, 84 and 73% for the 1st, 2nd and 3rd cycle, respectively. The scope of the reaction was expanded to other molecules showing the potential of this and other triazole-hydrochar-supported nanocatalysts. [Display omitted] •Hydrochar from coffee straw was functionalized with a triazole group (HD-TRz).•HD-TRz has been used as a support of palladium nanoparticles (PdNPs-HD-TRz).•The PdNPs-HD-TRz has been used in the Ullmann homocoupling reaction.•The green synthesis conditions have been used in the catalysis.•The material has been successfully used in different catalytic cycles.