High-performance triethylamine gas sensor with low working temperature based on amorphous derivative from ZIF-67

Although metal-organic framework (MOF) derivatives are expected to exhibit advanced gas sensing properties, few amorphous MOF derivatives have been synthesized and used as gas sensors because common synthetic methods usually yield crystalline derivatives. In this work, an amorphous derivative of ZIF-67 consisting of nanocubes with an average size of about 200 nm was synthesized by calcining ZIF-67 at 260 ℃. The amorphous derivative started to transform into crystalline Co ₃O ₄ at a calcination temperature of 270 ℃, during which the nanocubes collapse into nanoparticles. The amorphous derivative has a high specific surface area of 350.2 m ² /g and a high mesopore ratio of 77.3 %. Remarkably, the amorphous derivative of ZIF-67 delivers a significantly enhanced response of 74.8–100 ppm triethylamine (TEA) gas at a low working temperature of 100℃ (30 % relative humidity), which is superior to that of ZIF-67 and its crystalline derivative. In addition, the amorphous derivative offers higher selectivity, greater long-term stability and good response under high relative humidity conditions. The response and recovery times are 125 s and 88 s. The improved gas sensing performance is mainly attributed to the high adsorbed oxygen content, large specific surface area and higher porosity of the material. The synthetic method detailed here could facilitate the development of gas sensors based on amorphous materials.