Metal-Organic Framework-Based Composite Materials for Chemical Sensor Applications

Metal-organic frameworks (MOFs) consisting of metal ions and organic linkers are promising materials considering their large surface area and high porosity for applications in filtration and sensors. So far, various MOFs have been synthesized and demonstrated as chemical sensing layers.[1-4] Nevertheless, the insulative properties of conventional 3D MOFs limit their applications in electrochemical sensing materials. To address these issues, MOFs were incorporated with conductive materials such as carbon nanotubes (CNTs) and graphene and demonstrated in electrochemical sensing layers for gas and ion detections.<br/>In this presentation, we present the electrochemical sensing properties of MOF-based composites. To obtain electrical conductivity, carbon nanotubes (CNTs) were incorporated with MOFs (e.g., MOF-8 and UiO-66) by in-situ growth on the defective surface of CNTs. The chemical sensing properties of the composite materials were investigated by two different types of transduction techniques; i) chemiresistive-type and ii) cyclic voltammetry-type. In terms of chemiresistive-type sensors, we investigated the role of metal nodes and organic linkers in MOFs upon the injection of reactive gas species such as H₂S by spectroscopy analysis. In the case of the cyclic voltammetry sensor, the detection capability of various heavy metal ions such as Hg²⁺, Cd²⁺, and Pb²⁺ was investigated using CNT-ZIF-8 composite via redox reactions. The chemiresistive sensor was integrated with a wireless sensing module for application in real-time wireless detection of chemical species. The proposed MOF-based composites as sensing layers can be applied in various fields such as environmental monitoring and healthcare.<br/><br/><b>References</b><br/>[1] <u>Seon-Jin Choi</u>, Hack-Jong Choi, Won-Tae Koo, Daihong Huh, Heon Lee*, and Il-Doo Kim*, <i>ACS Applied Materials & Interfaces</i>, Vol. 9, No. 46, pp. 40593−40603, 2017.<br/>[2] Won-Tae Koo, Ji-Soo Jang, <u>Seon-Jin Choi</u>, Hee-Jin Cho, and Il-Doo Kim*, <i>ACS Applied Materials & Interfaces</i>, Vol. 9, pp. 18069-18077, 2017.<br/>[3] Won-Tae Koo, <u>Seon-Jin Choi</u>, Ji-Soo Jang, and Il-Doo Kim*, <i>Scientific Reports</i>, Vol. 7, No. 45074, 2017.<br/>[4] Won-Tae Koo, <u>Seon-Jin Choi</u>, Sang-Joon Kim, Ji-Soo Jang, Harry L. Tuller, and Il-Doo Kim*, <i>Journal of the American Chemical Society (JACS)</i>, Vol. 138, pp. 13431-13437, 2016.