Building porphyrin-based MOFs on MXenes for ppb-level NO sensing

Fractional exhaled nitric oxide (FeNO) is a significant biological signaling molecule. However, the detection of ppb-level nitric oxide (NO) still faces great challenges. Herein, we designed and prepared a porphyrin-based MOF (Co-TCPP(Fe)) with rod-like morphology which was assembled with MXene (Ti3C2Tx) through hydrogen bonding to offer a kind of chemiresistive NO sensing hybrid (Co-TCPP(Fe)/Ti3C2Tx). The Co-TCPP(Fe)/Ti3C2Tx-20 based sensor showed superior NO sensing performance at room temperature including high response (R-a/R-g = 2.0, 10 ppm), reliable repeatability, high selectivity, low practical limit of detection (pLOD, 200 ppb), and fast room temperature NO sensing response/recovery speed (95 s/15 s, 10 ppm). The study of the gas sensing mechanism demonstrated that reviving more unoccupied Fe-N-4 units to sense NO by forming a rod-like MOF architecture and facilitating charge transfer by constructing a Schottky junction of Co-TCPP(Fe)/Ti3C2Tx jointly contribute to the superior performance of the obtained Co-TCPP(Fe)/Ti3C2Tx based NO sensor. This work not only paves an avenue for fabricating bimetallic porphyrin-based rod-like MOFs, but also proposes a facile strategy of constructing Schottky junctions between MOFs and MXenes for high-performance chemiresistive gas sensors, which acts as a guide for fabricating MOF-based hybrid sensing materials in the future.