β-Cyclodextrin can solubilize the reactants, bind substrates selectively and catalyze chemical reactions by the interaction between β-cyclodextrin and substrates. During selective oxidation of p-methoxybenzaldehyde to p-methoxyphenol under supramolecular catalysis with β-cyclodextrin using H2O2/H3BO3/H2SO4 in water, β-cyclodextrin could form inclusion complexes with p-methoxybenzaldehyde and p-methoxyphenol, which effectively prevented them from continuous reaction and promoted the reaction selectivity. Various characterization methods including 1H NMR, UV-Vis and FT-IR were adopted to analyze the interaction between β-cyclodextrin and p-methoxybenzaldehyde, showing that the stable inclusion of β-cyclodextrin and p-methoxybenzaldehyde with a molar ratio of 1∶1 can be automatically formed in water, with the stability constant of the inclusion, Ka, being 358 and the standard Gibbs function of molar reaction, Δγ (298.15 K), being －14.577 kJ•mol－1. FT-IR analysis exhibits that aldehyde groups were mainly in the narrow mouth of the β-cyclodextrin in the inclusion complexes.

Key words: β-cyclodextrin, p-methoxybenzaldehyde, p-methoxyphenol, inclusion complex