Chemistry | 2019
Transistor-based work function measurement of metal-organic frameworks for ultra-low-power, rationally designed chemical sensors.
Abstract
A classic challenge in chemical sensing is selectivity. Metal-organic frameworks (MOFs) are an exciting class of materials because they can be tuned for selective chemical adsorption. Adsorption events trigger work function shifts, which can be detected with an chemical-sensitive field-effect transistor (power ~ microwatts). In this work, we use several case studies towards generalizing the sensing mechanism, ultimately towards our metal-centric hypothesis. HKUST-1 is used as a proof-of-principle humidity sensor. The response is thickness-independent, meaning the response is surface-localized. ZIF-8 is demonstrated as an NO2 sensing material, and the response is dominated by adsorption at metal sites. Finally, MFM-300(In) shows how standard hard-soft acid-base theory can be used to qualitatively predict sensor responses and that work-function shifts in MOFs can be a sensitive measure of MOF stability in reactive environments. This paper sets the groundwork for using the tunability of metal-organic frameworks for chemical sensing with distributed scalable devices.