Room-Temperature Photooxidation of CH to CHOH with Nearly 100% Selectivity over Hetero-ZnO/FeO Porous Nanosheets.

The huge challenge for CH photooxidation into CHOH lies in the activation of the inert C-H bond and the inhibition of CHOH overoxidation. Herein, we design two-dimensional in-plane -scheme heterostructures composed of two different metal oxides, with efforts to polarize the symmetrical CH molecules and strengthen the O-H bond in CHOH. As a prototype, we first fabricate ZnO/FeO porous nanosheets, where high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy affirm their in-plane -scheme heterostructure. Fourier transform infrared spectra and electron paramagnetic resonance spectra demonstrate their higher amount of ·CH radicals relative to the pristine ZnO porous nanosheets, in which density functional theory calculations validate that the high local charge accumulation on Fe sites lowers the CH adsorption energy from 0.14 to 0.06 eV. Moreover, the charge-accumulated Fe sites strengthen the polarity of the O-H bond in CHOH through transferring electrons to the O atoms, confirmed by the increased barrier from 0.30 to 2.63 eV for *CHO formation, which inhibits the homolytic O-H bond cleavage and thus suppresses CHOH overoxidation. Accordingly, the CHOH selectivity over ZnO/FeO porous nanosheets reaches up to nearly 100% with an activity of 178.3 μmol g, outperforming previously reported photocatalysts without adding any oxidants under room temperature and ambient pressure.