V2CTx MXene-derived porphyrin-based MOF modified with ZIF-67 as an ultra-stretchable and deformable double-network hydrogel for room temperature detection of dimethylamine

Stretchable and self-adhesive chemical sensors are highly appealing for wearable health and environmental monitoring applications. Here, for the first time, we report V2CTx MXene-derived Porphyrin-based MOF (VPMOF) modified with Zeolite imidazole framework-67 (ZIF-67) for the room temperature detection of dimethylamine. V-PMOF is synthesized from V2CTx MXene using tetrakis(4-carboxyphenyl)porphyrin (TCPP) as a ligand via a solvothermal route. Thereafter, an optimized wt% ratio (1:1) of ZIF-67 and V-PMOF crosslinked by PVA/polypyrrole (Ppy) is put for lyophilization which yields the V-PMOF@ZIF-67 double-network (DN) hydrogel. Detailed morphological assessment reveals dodecahedron-shaped ZIF-67 particles are evenly distributed on the V-PMOF sheets which are encapsulated in the polymer matrix. This three-dimensional polymeric structure of hydrogel largely enhances the active sites on the surface with abundant oxygen vacancies. The sensor exhibits a dynamic range of 1 ppm to 13 ppm with a low limit of detection (LOD = 3s/sigma) of 902 ppb towards dimethylamine detection. Further, quick response/recovery times (3 s/7 s) are observed along with high robustness to significant mechanical deformation, including twist (270 degrees), large-range bending, and up to 500% strain without affecting the sensing performance. The remarkable sensitivity is accredited to the abundance of O2 functional groups in polymer chains and the formation of Schottky heterojunction between V-PMOF and ZIF-67, facilitating charge transfer between the heterostructure to dimethylamine during sensing. In addition, the selfadhesive hydrogel-based sensor shows outstanding selectivity against other typical volatile organic compounds (VOCs) such as acetone, ethanol, ammonia, trimethylamine, aniline, and methanol. In overall, this work provides insight into designing extremely flexible sensitive dimethylamine gas sensor as innovative material.