Amino Acid-Assisted Construction of an MOF-on-MOFStructure for Highly Selective Detection of Triethylamine at Low Temperature

Metal–organic frameworks (MOFs), known for their exceptional gas permeability and abundant active sites, are a class of porous coordination polymers that can serve as ideal candidates for constructing advanced gas sensors. However, the limitations of low electrical conductivity and inadequate stability under extreme conditions hinder their advancements in gas-sensing applications. Moreover, a single MOF structure occasionally demonstrates insufficient selectivity toward specific gases, failing to meet stringent sensing requirements. To overcome these challenges, this study innovatively constructs an MOF-on-MOF architecture by etching Ti-MOF into a hollow cage-like structure with l-glutamic acid and connecting it with Ni²⁺ ions to form Ni-MOF via peptide bonds. The approach not only enhances the specific surface area and pore structure of the material but also facilitates carrier transport rates at the interface by effectively linking the two MOFs. The resultant MOF-on-MOF structure exhibits remarkable selectivity and sensitivity in detecting triethylamine gas at a low operating temperature of 140 °C, along with exceptional reproducibility and long-term stability. This work demonstrates a novel amino acid-assisted feasible and simple method to construct MOF-on-MOF material, showcasing immense potential in high-performance gas detection applications.