Active sites behavior on Ru@MIL-101(Cr) catalysts to direct alcohol to acetals conversion, an in situ FT-IR study of n-butanol and butanal

Comparing to homogeneous systems, direct alcohol to acetals conversion (DAAC) reaction through heterogeneous catalysts has obvious advantages of simple separation, less corrosion and waste. However, progress on this research is quite limited. Recently a breakthrough of Ru@MIL-101(Cr) catalyst was found with high selectivity and conversion for DAAC of aliphatic alcohol and diols towards desired products. In this study, time resolved in situ FT-IR was performed for capturing molecular-level information on the active sites of the catalysis system. Transients analysis of interaction between n-butanol/butanal and two active surface sites induced by Ru loading on MIL-101(Cr) provides key insight to the reaction, revealing that Ru@ MIL-101(Cr) confines the reaction to the ideal acidic sites between Ru nanoparticles and MIL-101(Cr) support for efficient process.

A: FT-IR time-resolved spectra for n-BuOH on Ru@MIL-101(Cr) showing at the 2000-1600 cm^-1 region. The FT-IR raw data of the 1920-1850 cm^-1 region at 300 s, 600s, 1200 s, 3600s are also listed (inset). B: Transient plot for n-BuOH adsorption on Ru@MIL-101(Cr). C: The tandem reaction model of DAAC on the Ru@MIL-101(Cr) catalyst.