Transferable Two-Dimensional Hydrophobic Metal-Organic Framework Encapsulation of MoS(2)-Based Humidity-Resistant NO(2) Sensors.

Humidity deteriorates the performance and detection accuracy of gas sensors, especially for two-dimensional (2D) materials with large specific surface areas. Here, we proposed a hydrophobic encapsulation strategy for molybdenum disulfide (MoS) using a porous metal-organic framework (MOF), poly[Fe(benzimidazole)], denoted as Fe(bim), to effectively suppress the adsorption of HO molecules. By ammonia-assisted chemical vapor deposition, large Fe(bim) flakes with lateral dimensions up to 72 × 72 μm were synthesized on mica. Owing to the hydrophilic nature of mica, the Fe(bim) flakes could be easily peeled off from mica using polydimethylsiloxane (PDMS) soaked in water and subsequently transferred onto MoS without contamination, forming a transferable hydrophobic encapsulation layer. The Fe(bim)/MoS heterojunction exhibited highly humidity-resistant NO sensing performance with only a 4.28% relative response variation across 40-70% relative humidity (RH) at room temperature. Compared to bare MoS, the response of Fe(bim)/MoS to 500 ppb NO increased from 0.53 to 2.03 at 70% RH, with a low practical limit of detection (LOD) of 20 ppb. This improvement not only arose from the hydrophobic Fe(bim) layer that suppressed HO adsorption on the MoS but also benefited from the charge transfer in Fe(bim)/MoS, demonstrating the effectiveness of this encapsulation strategy in mitigating humidity-induced sensing performance fluctuation.