A bio-inspired and switchable H/OH ion-channel for room temperature exhaled CO chemiresistive sensing

Inspired by the CO 2 -induced reversible activation mechanism of the slow anion channel 1 (SLAC1) in plant stomatal guard cells during plant photosynthesis, we designed and prepared a CO 2 - switchable H + /OH − ion channel (CSPH ion channel). A high-performance chemiresistive room temperature CO 2 sensor has been prepared based on this CSPH ion channel. The obtained CO 2 room temperature sensor γ-CD-MOF@RhB exhibits high sensitivity ( R g / R 0 = 1.50, 100 ppm), excellent selectivity, good stability (less than 5% reduction in 30 days response value), and 99.96% consistency with commercial infrared CO 2 meter. The practical limit of detection (pLOD) of the γ-CD-MOF@RhB sensor reaches 10 ppm at room temperature toward CO 2 , which is the lowest for reported MOF-derived chemiresistive room temperature CO 2 sensors so far. Ion conduction mechanism studies have shown that the CSPH ion channel behaves as a CO 2 -switchable H + /OH − ion channel with a switching point of approximately 60 000 ppm CO 2 . As an application attempt, the fabricated low pLOD CO 2 sensor has been used for human exhaled CO 2 detection to compare CO 2 concentration in the breath of individuals before and after exercise and COVID-19. It was also logically indicated that the average concentration of human exhaled CO 2 after COVID-19 recovery is different for undiseased subjects. A SLAC1-mimicking artificial CO 2 -switched proton/hydroxide (H + /OH − ) ion channel (CSPH ion channel) was developed for room temperature exhaled CO 2 chemiresistive sensing.