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<p>Achieving a room temperature solid state gas sensor that allows the precise detection of CO<sub>2</sub> gas at ppm level is crucial for measuring higher levels indoor and outdoor places. The room temperature with fast-response CO<sub>2</sub> sensors based on vertically layered heterostructures continues to be a challenging frontier in sensor development. In this work, we have successfully developed a vertical device for CO<sub>2</sub> sensing in the range of 500–2000&#xa0;ppm at 200&#xa0;°C. The strategies for synthesizing stable MOF (UiO-66 (Zr)) on 2D MXene (Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub>) layer have also been demonstrated. The sensing device was fabricated on ITO coated glass surface using a spin-coating method, with UV-ozone pretreatment to enhance substrate surface energy and improve adhesion. The structural and morphological characterization revealed the well-organized layered structure for UiO-66 (Zr)/Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub> with a BET surface area of 1840&#xa0;m<sup>2</sup>, pore size in the range 3.5–4&#xa0;nm, with pore volume 0.1398&#xa0;(cm<sup>3</sup>/g), led to fast response and recovery times. The vertically with ITO/Au/Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub>/UiO-66 (Zr)/Au configuration exhibited a higher gas response of ~ 36.67% at 200&#xa0;°C and 2000&#xa0;ppm with response and recovery times of ~ 1.0&#xa0;min and 3.1&#xa0;min, respectively. On the other hand, the Au/UiO-66 (Zr)/Au device showed a low gas response ~ 0.02% even at 450&#xa0;°C and response/recovery times of 0.7/3.0&#xa0;min. The device with pristine UiO-66 (Zr) have not shown a stable response even at 200&#xa0;°C. We also evaluated the charge transport regime in Zr-based UiO-66 and UiO-66 (Zr) /Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub> devices transitions from Poole–Frenkel conduction at lower temperatures to an Ohmic behavior at higher temperatures, which was strongly influenced by varying CO<sub>2</sub> concentration. These findings reveal that the temperature and concentration dependent conduction mechanisms are critical for optimizing vertical CO<sub>2</sub> sensors.</p> Graphical abstract <p></p>

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Enhanced CO2 detection using Schottky conduction mechanism in 2D MOF/MXene hybrid vertical sensing device

  • 期刊论文

  • 发表日期：

    2026年1月2日

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  • Syeda Maria Batool,
  • Syeda Sitwat Batool,
  • Mushtaq Ahmad,
  • Muhammad Umair Hassan,
  • Meehan Miranda,
  • Thomas DeSutter,
  • Benjamin D. Braaten,
  • Peter G. Oduor

摘要

Achieving a room temperature solid state gas sensor that allows the precise detection of CO2 gas at ppm level is crucial for measuring higher levels indoor and outdoor places. The room temperature with fast-response CO2 sensors based on vertically layered heterostructures continues to be a challenging frontier in sensor development. In this work, we have successfully developed a vertical device for CO2 sensing in the range of 500–2000 ppm at 200 °C. The strategies for synthesizing stable MOF (UiO-66 (Zr)) on 2D MXene (Ti3C2Tx) layer have also been demonstrated. The sensing device was fabricated on ITO coated glass surface using a spin-coating method, with UV-ozone pretreatment to enhance substrate surface energy and improve adhesion. The structural and morphological characterization revealed the well-organized layered structure for UiO-66 (Zr)/Ti3C2Tx with a BET surface area of 1840 m2, pore size in the range 3.5–4 nm, with pore volume 0.1398 (cm3/g), led to fast response and recovery times. The vertically with ITO/Au/Ti3C2Tx/UiO-66 (Zr)/Au configuration exhibited a higher gas response of ~ 36.67% at 200 °C and 2000 ppm with response and recovery times of ~ 1.0 min and 3.1 min, respectively. On the other hand, the Au/UiO-66 (Zr)/Au device showed a low gas response ~ 0.02% even at 450 °C and response/recovery times of 0.7/3.0 min. The device with pristine UiO-66 (Zr) have not shown a stable response even at 200 °C. We also evaluated the charge transport regime in Zr-based UiO-66 and UiO-66 (Zr) /Ti3C2Tx devices transitions from Poole–Frenkel conduction at lower temperatures to an Ohmic behavior at higher temperatures, which was strongly influenced by varying CO2 concentration. These findings reveal that the temperature and concentration dependent conduction mechanisms are critical for optimizing vertical CO2 sensors.

Graphical abstract