Ionic-Liquid-Engineered Chitin Nanofiber Supports for Low-Loading Pd Catalysts

This study reports an ionic-liquid (IL)-enabled strategy for engineering chitin nanofiber supports that allows for the formation of monometallic Pd, Ag, and Au catalysts, as well as Pd-Au co-loaded catalyst. High-molecular-weight chitin, extracted from shrimp shells using 1-ethyl-3-methylimidazolium acetate ([C₂C₁im][OAc]), is regenerated and electrospun into free-standing nanofiber mats, followed by partial deacetylation of the accessible nanofiber interface to introduce primary amine functionalities while largely preserving the chitin crystalline framework. Metal precursors were first immobilized at the modified chitin nanomat interface at pH ≈ 2, followed by nanoparticle formation upon exposure to alkaline borate buffer (pH ≈ 9.2-10). STEM analysis shows particle sizes of Pd 3.2 ± 1.0 nm, Au 6.4 ± 2.6 nm, and Ag 2.6 ± 1.2 nm. The co-loaded Pd-Au sample likewise exhibited nanoscale, well-dispersed particles with no large aggregates observed within the examined STEM regions. Catalytic performance is evaluated using the Suzuki-Miyaura coupling of bromobenzene with phenylboronic acid as a benchmark reaction. The Pd-chitin nanomats achieve >99% conversion and ≥99% selectivity at gravimetrically estimated Pd loadings as low as 0.012-0.017 mol% under the conditions examined.