Infrared study on the dehydroxylation of C-60-loaded MCM-41

The dehydroxylation behavior of two MCM-41 samples with and without C-60 was monitored by infrared spectroscopy. Both samples contain isolated and hydrogen-bonded silanol groups, but with different distributions. Without C-60, the hydrogen-bonded species are eliminated at elevated temperatures under vacuum whereas the isolated ones remain. Loading C-60 in the MCM-41 materials greatly changes their dehydroxylation behavior. When the MCM-41:C-60 weight ratio is 10:1, at about 400 degrees C under vacuum, the isolated silanols are reduced to a certain degree whereas the hydrogen-bonded hydroxyls become more resistant to thermal treatment by comparison with those in the parent C-60-free samples. Increasing the loading amount of C-60 to a MCM-41:C-60 weight ratio of 10:3 results in complete removal of both isolated and hydrogen-bonded silanols, at about 350 degrees C. However, the two MCM-41 samples exhibit different infrared spectra at lower evacuation temperatures in the presence of C-60, indicative of a discrepancy in the dehydroxylation process between them. It is postulated that during the dehydroxylation, C-60 captures hydroxyls from the silanol groups of MCM-41 to form C-H and C-OH species, followed by condensation of the C-OH groups and/or combination of C-OH with C-H.