Metal-organic frameworks (MOFs) present specific adsorption sites with varying electron affinity which are uniquely conducive to selective gas sensing but are typically large-band-gap insulators. On the contrary, multiwall carbon nanotubes (MWCNTs) exhibit superior mesoscopic transport exploiting strong electron correlations among sub-bands below and above the Fermi level at room temperature. We synergize them in a new class of nanocomposites based on zeolitic imidazolate framework-8 (ZIF-8) and report selective sensing of CH in ∼10 parts-per-billion (ppb) with a determined limit of detection of ∼0.22 ppb, hitherto unprecedented. The observed selectivity to CH over non-polar CO, polar volatile organic compounds, and moisture has roots in competing electron-sharing mechanisms at its different adsorption sites. This important result provides a significant reference to guide future MOF-related composite research to achieve the best sensing performance. On molecular adsorption, MWCNTs facilitate electrical transport via manipulating the ZIF-8 band gap to show a p-type semiconductor behavior with lower activation energy to induce a measurable resistance change. Excellent repeatability and reversibility are shown. A carbon-engineered MOF composite has the potential to actuate similar selective response to low reactive gases via carrier manipulation in the energy band gap.
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http://dx.doi.org/10.1021/acssensors.2c01796 | DOI Listing |
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