Background: The unique physiochemical properties of nanoparticles as compared to their
bulk state make them highly useful in the area of catalysis, fuel cell development, photonics, medicines,
solar cell and biomedical imaging. The small size structures of nanoparticles are certainly very unstable
mainly because of their high surface energies and large surface area. To produce stable nanoparticle, it
is important to reduce the particle growth reaction (to avoid agglomeration). The advantage of the use of
SBA-15 material as support also includes its high surface-to-volume ratio, variable framework compositions
and high thermal stability. Thus SBA-15 exhibits mainly mesoporous structure and possesses a
small amount of micropores. The large pore size of this mesoporous material can mitigate the diffusion
barrier for the reactants and the products. In some recent technical reports, silica materials with grafted
silicon hydride groups have been successfully applied for the synthesis of gold, silver and palladium
nanoparticles. With respect to common normal hydrogen reduction, direct reduction of ions followed by
varying concentration of metal salt and reduction time, the hydride silica surface offers the controlled
shape and size selective metal nanoparticles.
Methods: In the present report, we have exploited the catalytic application of mesoporous silica supported
Ru metal nanoparticles for CO2 hydrogenation reaction. Silica hydride groups, possessing reducing
properties, grafted to the surface of silica allowed obtaining metal nanoparticles immediately at reducer
attachment position. Ru-silica (SBA-15-xRu) catalysts were characterized by different physiochemical
methods and tested for CO2 hydrogenation reaction.
Results: A series of SBA-15 supported Ru catalysts were prepared with 1, 2 and 3% (by weight) Ru
metal loading followed by impregnation method and well-characterized by sophisticated analytical
techniques. Among all the SBA-15-xRu catalysts, SBA-15-3Ru catalyst was found to be highly active
for hydrogenation of CO2 to formic acid. Low catalyst loading, ligand free approach, simple reaction
protocol and catalyst recycling are major merits of this proposed work.
Conclusion: In summary, Ru nanoparticles synthesis on the surface of SBA-15 with different structural
characteristics was studied. The SBA-15-3Ru catalyst was found to be highly efficient for hydrogenation
of CO2 to formic acid. CO2 hydrogenation reaction enjoyed the catalytic system and offered the
corresponding hydrogenated reaction product in good yield and selectivity. Good catalyst recycling, low
catalyst loading, simple work up procedure and easy catalyst preparation step were the major outcomes
of this proposed protocol.