Abstract: Sorption of benzene onto Cu-montmorillonite was characterized by Fourier transform infrared (FTIR) spectroscopy and 13C magic angle spinning nuclear magnetic resonance (MAS NMR). Under anhydrous conditions, chemisorption of benzene in the interlamellar region of Cu-montmorillonite led to the formation of a dark red surface complex that exhibited a vibrational spectrum similar to that of doped poly-p-phenylene. When the benzene sorption reaction was carried out under high relative humidity conditions, polymerization of benzene did not occur. The FTIR spectrum of the surface complex formed under wet conditions exhibited vibrational bands that could not be assigned to those of the parent benzene molecule or to those of previously observed chemisorbed Type I or Type II complexes. 13C MAS NMR spectra of 13C-enriched benzene sorbed onto Cu-montmoritlonite powder showed the presence of two groups of peaks that could be assigned to aromatic and aliphatic carbon respectively.