Selective Preparation of Mo₂N and MoN with High Surface Area for Flexible SERS Sensing

γ-Mo₂N and δ-MoN are the two most important molybdenum nitrides, but controllable preparation of them with high surface area has not been achieved. Herein, we achieved selective preparation of γ-Mo₂N and δ-MoN. The key factor for the selective preparation of γ-Mo₂N and δ-MoN is to control the crystal phase of the precursor MoO₃. In H₂O and NH₃ mixed gas, the α-MoO₃ nanoribbons are nitridated to obtain γ-Mo₂N single-crystal porous nanobelts, while the h-MoO₃ prisms are nitrided to obtain δ-MoN hierarchical porous columns. The corrosion effect of H₂O plays a key role in the formation of single-crystal porous structure. The γ-Mo₂N flexible membrane composed of the single-crystal porous nanobelts exhibits strong localized surface plasmon resonance and surface enhanced Raman scattering effect, which show highly sensitive response to polychlorinated phenol.