An all-inorganic three-dimensional polyoxoniobate framework with ppb-level chemiresistive sensing for ammonia

Fabrication of gas sensors with high sensibility appears particularly important due to the urgent demand for toxic gases monitoring in public safety and atmosphere detection, especially for the detection requirement of ultra-low concentration gases. Here, we present a rare three-dimensional (3D) all-inorganic polyoxoniobate (PONb) framework based on Cu4@Nb29 secondary building units linked with both tetranuclear Cu4 (OH) 5 clusters and mononuclear Cu (H2O) 2+ units. Remarkably, this 3D PONb framework exhibits an ultrasensitive response to NH3 with a lowest limit of detection of 1. 64 ppt up to now. Furthermore, the NH3 induced single-crystal-to-single-crystal transformation as well as density functional theory analysis reveal that the strong coordination affinity of Cu (H2O) 2+ linker for NH3, along with more injection of charge into the framework, results in a ultrasensitivity chemiresistive responses to NH3, at atomic-level insight.