Conductive Stimuli-Responsive Coordination Network Linked with Bismuth for Chemiresistive Gas Sensing

This
paper describes the design, synthesis, characterization, and
performance of a novel semiconductive crystalline coordination network,
synthesized using 2,3,6,7,10,11-hexahydroxytriphenylene (HHTP) ligands
interconnected with bismuth ions, toward chemiresistive gas sensing.
Bi­(HHTP) exhibits two distinct structures upon hydration and dehydration
of the pores within the network, Bi­(HHTP)-α and Bi­(HHTP)-β,
respectively, both with unprecedented network topology (2,3-c and
3,4,4,5-c nodal net stoichiometry, respectively) and unique corrugated
coordination geometries of HHTP molecules held together by bismuth
ions, as revealed by a crystal structure resolved via microelectron
diffraction (MicroED) (1.00 Å resolution). Good electrical conductivity
(5.3 × 10–3 S·cm–1)
promotes the utility of this material in the chemical sensing of gases
(NH3 and NO) and volatile organic compounds (VOCs: acetone,
ethanol, methanol, and isopropanol). The chemiresistive sensing of
NO and NH3 using Bi­(HHTP) exhibits limits of detection
0.15 and 0.29 parts per million (ppm), respectively, at low driving
voltages (0.1–1.0 V) and operation at room temperature. This
material is also capable of exhibiting unique and distinct responses
to VOCs at ppm concentrations. Spectroscopic assessment via X-ray
photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopic
methods (i.e., attenuated total reflectance-infrared spectroscopy
(ATR-IR) and diffuse reflectance infrared Fourier transformed spectroscopy
(DRIFTS)), suggests that the sensing mechanisms of Bi­(HHTP) to VOCs,
NO, and NH3 comprise a complex combination of steric, electronic,
and protic properties of the targeted analytes.