Methanol-Ethanol Discrimination and Selective Sensing Enabled by Molecular Sieving in Conductive MOFs

Methanol presents a significant health risk because of its volatility and toxicity. Its close chemical similarity to ethanol increases the likelihood of accidental ingestion through contaminated beverages. Here, we report chemiresistive sensors that selectively distinguish methanol from ethanol under ambient conditions. The sensors consist of single-walled carbon nanotubes (CNTs) functionalized with conductive metal-organic frameworks (cMOFs) constructed from 2,3,7,8,12,13-hexahydroxytetraazanaphthotetraphene (HHTT). Trinuclear intra-pore clusters (IPCs) located within the honeycomb channels of HHTT-based cMOFs govern methanol sensing by increasing the density of adsorption sites and constraining molecular diffusion through the pores. Mg-HHTT, in which the pores are largely occupied by IPCs, enhances the methanol response of CNT@cMOF composites while suppressing transport of ethanol and larger alcohols. In contrast, isostructural Ni-HHTT and Cu-HHTT analogues, which lack a high density of IPCs, exhibit substantially lower sensitivity and selectivity. Density functional theory and molecular dynamics simulations support a sensing mechanism based on IPC-mediated molecular sieving. Sensor tests using methanol-spiked liquors demonstrate selective methanol detection in complex beverage matrices under practical ambient conditions.