Rich vacancy-hosted-nitrogen sites on ZIF-derived porous carbon for enhanced humidity sensing

Abstract

Humidity sensing based on carbon-based materials has received immense attention in recent years. However, limitations in the surface modification and structural design of carbon-based materials, along with an incomplete understanding of the sensing mechanisms, have hindered improvements in humidity performance. In this study, a dodecahedral porous carbon material decorated with vacancy-hosted nitrogen (Va-N) sites is synthesized using a sacrificial Zn within a preformed zeolitic imidazolate framework (ZIF)-derived porous carbon matrix, which is demonstrated for the first time as an advanced humidity-sensitive material. Density functional theory (DFT) simulations indicate that vacancy defects significantly alter the electronic structure of adjacent nitrogen sites and carbon planes, facilitating the adsorption and activation of water molecules. Moreover, the porous carbon network structure further enhances the exposure of Va-N sites, improves electronic transport, and promotes the migration of water molecules. The optimized sensor exhibits a wide detection range (0.3–98 % RH), high sensitivity (67.7–92.8 % of relative resistance change, the response limit is 100 %), low hysteresis (1.5 %), good linearity (R² > 0.996), high resolution (0.5 %, at low humidity levels), as well as excellent stability. Additionally, this humidity sensor demonstrates good flexibility and potential applications in non-contact control, skin humidity detection, and intelligent respiratory monitoring systems. This work provides new inspiration for fabricating novel defects in carbon-based materials, transforming them into advantages for sensing applications