An incoherent inelastic neutron scattering investigation of the vibrational spectrum of phenyl-modified (C₆H₅–) mesoporous silica and its variations in the presence of sorbed benzene (C₆H₆) and of sorbed deuteriobenzene (C₆D₆)

Abstract

Mesoporous phenyl-modified silica has been prepared by a co-condensation method and has been characterised via infrared and nuclear magnetic resonance (29Si, 13C) spectroscopies and thermal analysis (TG/DTA). Incoherent inelastic neutron scattering (IINS) at T = 10 K has been used to record vibrational spectra dominated by modes involving motion of hydrogen (1H) for h6-benzene (C6H6) and for phenyl-modified silica (a) outgassed, (b) with an adsorbed monolayer of h6-benzene, (c) with an adsorbed monolayer of d6-benzene (C6D6) and (d) saturated with h6-benzene. Spectral features are assigned and discussed in terms of modes of H-containing Si-attached phenyl groups and benzene molecules in a range of environments. The modes of the phenyl rings are essentially unchanged in the presence of a monolayer. The structural arrangement of pore-filling benzene molecules differs from that in bulk benzene, this being evident in spectral differences.