Selective Hydrogenation of Polyunsaturated Fatty Acid Methyl Esters over Bifunctional Ligand-Modified Pd/MIL-101(Cr) Catalysts

Highly dispersed palladium nanoparticles (Pd NPs) were incorporated into MIL-101(Cr) frameworks functionalized with bifunctional ligands for the liquid-phase hydrogenation of polyunsaturated fatty acid methyl esters (FAMEs). A series of amino- and carboxylic-acid-containing ligands─ethylenediamine (en), diethylenetriamine (DET), alanine (AN), 4-aminobutyric acid (ABA), 5-aminovaleric acid (AVA), glutamic acid (GA), and adipic acid (AA)─were grafted onto MIL-101(Cr), followed by Pd loading (0.5 wt %). Spectroscopic and structural analyses confirmed ligand coordination to both Cr nodes and Pd species. Catalysts bearing ABA, AVA, and GA exhibited Pd⁰ dispersion (<1 nm), yielding high turnover frequencies (up to ∼15,400  h^–1) and >94% selectivity for monounsaturated FAMEs. In contrast, strong Pd–N interactions in en- and DET-grafted materials suppressed Pd⁰ formation, reducing activity. Hot filtration and recyclability tests confirmed high catalyst stability and negligible Pd leaching. The bifunctional ligand architecture effectively tunes Pd speciation and activity, providing a robust platform for selective and reusable hydrogenation catalysts.

Palladium nanoparticles were incorporated into bifunctional ligand-modified MIL-101(Cr) frameworks for selective hydrogenation of polyunsaturated fatty acid methyl esters. Ligands containing amino and carboxylic groups influenced Pd dispersion and catalytic performance. Catalysts with ABA, AVA, and GA achieved high Pd⁰ dispersion (<1 nm), excellent activity (up to ∼15,400 h⁻¹), and >94% selectivity for monounsaturated products. In contrast, Pd−N interactions in other ligands reduced activity. The catalysts demonstrated strong stability and reusability, highlighting the ligand’s role in tuning Pd speciation.