. Comprehensive characterization by TGA, XPS, atomic absorption spectroscopy (AAS), and Energy-dispersive X-ray spectroscopy (EDAX) confirmed successful surface modification and palladium immobilization. XPS analysis indicated that palladium is present in the + 2 oxidation state and coordinated to the phenanthroline nitrogens. SBA-15@PHEN-Pd(II) efficiently catalyzed CO-free carbonylation of aryl halides to carboxylic acids using a formic acid/DCC system. Systematic optimization identified DMF and NaOH at 120 °C as optimal, enabling up to 76% yield across a broad substrate scope. Reactivity followed the order Ar-I > Ar-Br > Ar-Cl, and substrates bearing electron-withdrawing substituents exhibited enhanced reactivity. Negligible palladium leaching was observed, and hot filtration experiments confirmed the heterogeneous nature of the catalyst. SBA-15@PHEN-Pd(II) exhibits sustained catalytic activity over six consecutive cycles, highlighting its stability and efficiency as a CO-free carbonylation catalyst.
Fathinejad et al. (Wed,) studied this question.