Large Conductance Modulation from CO ₂ Adsorption on a Hydrated Solid-Supported Percolative Amine Network

Amine functionalization of hexagonal boron nitride (h-BN) is analyzed for potential applications in chemiresistive sensing and CO2 capture. The amine groups are functionalized on the edges of layered h-BN flakes, resulting in a quasi-1D network that serves this dual functionality. We demonstrate a large change in electrical conductance in functionalized h-BN (referred to as FBN) upon hydration. In hydrated FBN, the percolative amine network, together with adsorbed water, serves as a transport channel for rapid proton transport. This results in an 8 orders of magnitude enhancement in electrical conductance from the dry to the hydrated state with 5 wt % water loading. The same network also hosts the synergistic interplay of CO2 and water chemistry. Water-mediated CO2 sorption disrupts these transport channels, leading to a decrease in conductance up to 2 orders of magnitude. Physisorbed CO2 does not affect the electrical conductance under anhydrous conditions. In situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) studies reveal that humid conditions promote CO2 adsorption, with formation of bicarbonates, carbonates, and carbamic acid. Electrical studies complemented by spectroscopy reveal that the efficiency of CO2–amine–water interactions is maximum at intermediate humidity and decreases at higher humidity due to the formation of water clusters. A prototypical FBN system that can facilitate the electrical monitoring of CO2 is demonstrated.