Sol-gel preparation of helical silicate containing palladium oxide nanoparticles and the application for nitration of aromatic compound

Two palladium-containing silicates are prepared through sol-gel, and doping of L-sodium lactate plays a key role for giving helical morphology. The helical silicate is modified by chiral sulfonyl chloride in order to modulate coordination environment of palladium for enhanced catalysis. The porosity, composition, crystalline nature and bulk chirality have been studied too. All synthetic silicates show high yields for nitration of arenes by using available nitro-source. Both solvent acidity and oxidant seem crucial to nitration more than others. The conversion of larger arene is related to catalyst porosity, and modification of silicate with chiral sulfonyl chloride shows varied results. Furthermore, two catalysts exhibit renewable recycling behaviors, proving their interior palladium could be utilized. Lastly, a tetravalent palladium-facilitated mechanism is proposed. This wok may contribute to the design and catalytic application of nanosized or microsized silica material with particular morphology.