Microwave-exfoliated 2D oligo-layer MoO3-x nanosheets with outstanding molecular adsorptivity and room-temperature gas sensitivity on ppb level

Large specific surface area and oxygen defects of metal oxides are the dominant factors to affect performances related to surface adsorption processes, and have been fully considered in the synthesis of materials. Understanding completely the effect of oxygen vacancies on the structure and the interaction with reactants is still under process. Here, for the first time, oxygen deficient two-dimensional (2D) oligo-layer molybdenum trioxide (MoO3-x) nanosheets with large aspect ratio of ∼670, were fabricated via a convenient microwave-assisted exfoliation method. The effect of oxygen vacancies on the surface adsorption of molecules was comprehensively investigated with experiments and DFT calculations. From the analysis of molecular dynamics and molecular electrostatic potential results, the enlarged interlayer spacings and oxygen vacancies working as the capture centers for negatively charged groups made 2D oligo-layer MoO3-x nanosheets promising for the adsorption for various organic molecules. Especially, a high value of ∼1290 mg/g rarely reported before was achieved for the adsorption of methylene blue. Benefited from the enlarged adsorption energies to gas molecules and the preferential adsorption of oxygen molecules in ambient atmosphere, p-type gas sensors based on 2D oligo-layer MoO3-x nanosheets were fabricated, which exhibited superior gas sensing performance to ethanol, acetone and hydrogen sulfide at room temperature. This work proposed an effective approach for synthesis of 2D nanomaterials, and underscored the importance of oxygen vacancies into 2D structures for different applications.