Room-Temperature CO<sub>2</sub> Monitoring Platform Enabled by Alkali Metal Functionalization of a Mg-MOF-74-Based QCM Sensor
Xukun Wang, Xiaoyi Xu, Tingting Zhou, Tong Zhang
Abstract
Carbon dioxide (CO 2 ) detection is indispensable for monitoring climate change, ensuring air quality, managing industrial processes, and safeguarding human health. Nevertheless, the chemical inertness and stability of CO 2 pose significant challenges in advancing detection technologies in practical applications. In order to overcome these challenges, nanoscale MOF-74 metal–organic frameworks (MOFs) functionalized with alkali metals (Li, Na, and K) have been synthesized for the effective detection of the CO 2 gas. The sensing results indicate that the Li–Mg-MOF-74-based quartz crystal microbalance (QCM) CO 2 sensors demonstrate excellent properties, such as very high sensitivity, rapid response/recovery time (84 s/69 s), broad detection range (300–10000 ppm), and remarkable selectivity at room temperature. The enhanced performance benefits from the increased electrostatic force and Lewis’s acidity resulting from alkali metal ions (Li + ) and open metal sites (Mg 2+ ). In addition, the equilibrium constant of CO 2 on the sensor surface was calculated by the Langmuir adsorption isotherm model, revealing spontaneous and robust adsorption behavior. These results indicate that alkali-metal-modified Mg-MOF-74 materials have great potential for practical CO 2 detection and provide a feasible solution for the design of high-performance, room-temperature CO 2 sensing platforms.