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 2 ) using a porous metal-organic framework (MOF), poly[Fe(benzimidazole) 2 ], denoted as Fe n (bim) 2n, to effectively suppress the adsorption of H 2 O molecules. By ammonia-assisted chemical vapor deposition, large Fe n (bim) 2n flakes with lateral dimensions up to 72 × 72 μm were synthesized on mica. Owing to the hydrophilic nature of mica, the Fe n (bim) 2n flakes could be easily peeled off from mica using polydimethylsiloxane (PDMS) soaked in water and subsequently transferred onto MoS 2 without contamination, forming a transferable hydrophobic encapsulation layer. The Fe n (bim) 2n /MoS 2 heterojunction exhibited highly humidity-resistant NO 2 sensing performance with only a 4.28% relative response variation across 40–70% relative humidity (RH) at room temperature. Compared to bare MoS 2, the response of Fe n (bim) 2n /MoS 2 to 500 ppb NO 2 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 n (bim) 2n layer that suppressed H 2 O adsorption on the MoS 2 but also benefited from the charge transfer in Fe n (bim) 2n /MoS 2, demonstrating the effectiveness of this encapsulation strategy in mitigating humidity-induced sensing performance fluctuation.