Metal-organic frameworks and porous polymers-based nanomaterials for chemical sensors

Abstract

Highly sensitive and selective chemical sensors are needed for use in a wide range of applications such as environmental toxic gas monitoring, disease diagnosis, and food quality control. Although some chemiresistive sensors have been commercialized, grand challenges still remain: ppb-level sensitivity, accurate cross-selectivity, and long-term stability. Metal–organic frameworks (MOFs) with record-breaking surface areas and ultrahigh porosity are ideal sensing materials because chemical sensors highly rely on surface reactions. In addition, MOFs can be used as a membrane to utilize their unique gas adsorption/separation characteristics. Furthermore, the use of MOFs as precursors enables facile production of various nanostructures is further combined with other functional materials. In addition to MOFs, porous polymers open a new way for the development of chemiresistors. Particularly, porous ion exchange polymers enable a facile decoration of ultrasmall and well-dispersed nanoparticles on various substrates via counter-ion exchange and following activation process. Based on these fascinating features of MOFs and porous polymers, in this thesis, comprehensive overview and studies in chemiresistive sensors developed by MOFs and porous ion exchange polymers are presented, in order to elucidate reaction mechanisms and address limitations in MOFs and porous polymers based chemical sensors. The underlying sensing mechanisms for various MOF- and porous polymer-based materials are discussed, and the correlation of sensing properties with structures, surface chemistry, and electronic properties is explained. In addition, the discussion of each material emphasizes key advances and strategies to develop superior chemical sensors. Finally, the thesis concludes with a brief outlook, some foresighted ideas, and future directions.