Three-Dimensional Assemblages of Metal Silicate for Catalytic CO2 Conversion to Methanol and Adsorptive Pollutant Removal

Sto''ber silica nanospheres weretransformed into zincsilicate nanoflowers and further functionalized into an active catalystfor the CO2-to-MeOH reaction, which was evaluated by themethylene blue adsorption test. Morphologicaltransformation was performed on Sto''ber silicananospheres (ca. 270 nm in diameter) and transmuted into either ZnSiO(zinc silicate) nanoflowers or MgSiO (magnesium silicate) nanoflowers(600-800 nm in diameter) through a facile hydrothermal process.The zinc silicate materials were then chosen for incipient wetnessimpregnation to imbue them with different levels of Cu and Zn dopingdue to the well-established elemental synergy of Cu and Zn towardmethanol synthesis via CO2 hydrogenation. Characterizationresults concur that zinc silicate nanoflowers loaded with copper-(II)oxide were formed after incipient wetness impregnation. Three as-synthesizedcatalyst candidates with different copper loadings were then evaluatedfor CO2 hydrogenation and compared against an industrialcatalyst. After the reaction, high-resolution transmission electronmicroscopy (HRTEM) with energy-dispersive X-ray (EDX) elemental mappingreveal that petite Cu nanoparticles formed on the petals of the impregnatedzinc silicate nanoflowers. Experimental results show that all catalystmaterials have an exceptional high methanol selectivity, with overallperformance exceeding that of the industrial catalyst at per Cu basis.Both ZnSiO and MgSiO were also evaluated through a simple methyleneblue adsorption test. Hence, through deliberate morphological controland chemical transformation, superficially inert Sto''ber silicananospheres were functionalized into transition- and earth-alkalinemetal silicates, which exhibit catalytic and adsorptive propertieswith a nanoflower morphology that prevents interstacking of nanosheets.

Automated summary

Sto''ber silica nanospheres were transformed into zinc silicate nanoflowers and used as an active catalyst for the CO2-to-MeOH reaction. The zinc silicate nanoflowers loaded with copper-(II) oxide showed excellent methanol selectivity in the reaction. This study demonstrates the potential of using these functionalized nanoflowers for efficient CO2 conversion into methanol.