Molecular Recognition and Charge Transport in Integrated Covalent Organic Frameworks-Carbon Nanotube Hybrids for Selective Gas Sensing.

Abstract

Translating molecular recognition in porous frameworks into stable electronic signals remains a central challenge for framework-based electronic materials. Herein, we establish a covalent design strategy that co-engineers molecular recognition and charge transport within a single framework-conductor architecture by stepwise integrating selective adsorption in the porous COF with efficient charge transport through the CNT scaffold, thereby enabling direct electronic transduction of host-guest interactions without external conductive additives or post-processing. The COF-CNT sensor detects CO2 rapidly and reversibly at room temperature (response/recovery: ∼36 s/∼58 s), remains stable under humid and mixed-gas conditions typical of petroleum environments, shows a linear chemiresistive response from 300-3000 ppm CO2, and is selective against CH4, C2H6, C3H8, and H2S. Density functional theory calculations indicate significantly stronger adsorption of CO2 (-0.71 eV) than the interfering gases, together with a calculated electron transfer of 0.12 e from the CNT to the adsorbate in the modeled CO2 adsorption configuration. Combined with the experimentally observed resistance decrease, these results are consistent with electron withdrawal from the hole-dominated transport behavior commonly observed in air-exposed CNT networks, which would increase the hole-carrier concentration and contribute to electronic transduction. This work defines a general construction-based paradigm for framework electronics, in which adsorption selectivity and electronic functionality are covalently codesigned.