Highly conjugated three-dimensional van der Waals heterostructure-based nanocomposite films for ultrahigh-responsive TEA gas sensors at room temperature

Abstract

Covalent organic frameworks (COFs) have emerged as next-generation materials with predesigned pi-electronic skeletons and highly ordered topological structures, which are promising for rapid gas sensing detection. COFs combined with carbon nanomaterials and metal oxide semiconductor (MOS) are conducive for the construction of high-quality van der Waals heterojunctions and the design of potential environmental sensors owing to the synergies between the functional components. Herein, we report a novel strategy for fabricating controllable core-shell structured COFs@SnO2@carbon nanospheres, which are composed of the SnO2@carbon nanospheres' (SnO2@CNS) hybrid core and Pt-functionalized COFs as the shell by sequential post-synthetic functionalization, and the application of COFs@SnO2@CNS-based nanocomposite films for efficient and selective sensing performance toward triethylamine (TEA). The ultrasensitive gas sensor exhibits an excellent sensing performance under 90% RH, such as the high sensitivity of 95.1 to 2 ppm TEA with the response and recovery times of 7 s and 5 s, detecting trace concentrations of TEA down to 0.2 ppm (S = 22.8) at room temperature. In particular, we applied machine learning methods, including principal component analysis (PCA) and support vector machine (SVM), to analyze the sensing performance of the COFs@SnO2@CNS-based sensor and found that the combined effects of the core-shell van der Waals heterostructures contributed to the improvement of the sensing performance of the sensor.