Efficient catalysts of surface hydrophobic Cu-BTC with coordinatively unsaturated Cu(I) sites for the direct oxidation of methane
Wencui Li, Zhi Li, Hang Zhang, Pengxiao Liu, Zean Xie, Weiyu Song, Baijun Liu, Zhen Zhao
Abstract
Selective oxidation of methane to organic oxygenates over metal–organic frameworks (MOFs) catalysts at low temperature is a challenging topic in the field of C1 chemistry because of the inferior stability of MOFs. Modifying the surface of Cu-BTC via hydrophobic polydimethylsiloxane (PDMS) at 235 °C under vacuum not only can dramatically improve its catalytic cycle stability in a liquid phase but also generate coordinatively unsaturated Cu(I) sites, which significantly enhances the catalytic activity of Cu-BTC catalyst. The results of spectroscopy characterizations and theoretical calculation proved that the coordinatively unsaturated Cu(I) sites made H 2 O 2 dissociative into •OH, which formed Cu(II)-O active species by combining with coordinatively unsaturated Cu(I) sites for activating the C−H bond of methane. The high productivity of C1 oxygenates (CH 3 OH and CH 3 OOH) of 10.67 mmol g cat. −1 h −1 with super high selectivity of 99.6% to C1 oxygenates was achieved over Cu-BTC-P-235 catalyst, and the catalyst possessed excellent reusability.