Ionic-Liquid–Assisted Charge Transport in E-Jet-Printed Conductive MOFs on Textiles: From Cu₃(HHTP)₂@PLA to a General Design Playbook for Wearable NOx Gas Sensors

Abstract

Conductive metal-organic frameworks (cMOFs) have emerged as promising transduction media for room-temperature gas sensing. Electrohydrodynamic (E-jet) printing of ionic-liquid (IL) functionalized Cu3(HHTP)2 onto electrospun polylactic acid (PLA) textiles yields a chemiresistive nitric oxide (NO) sensor with unusually high electronic conductivity (19.23 μS cm-1) and strong response (≈ 570% at 100 ppm), while maintaining textile compliance. Building on this result, we synthesize the literature on IL-MOF charge transport, E-jet process-structure-property links, and textile reliability to propose a practical design playbook for wearable NOx monitoring. Using PRISMA-guided screening, we identify 123 sensor studies (2019–2025) relevant to: (i) cMOF/IL films and thin-film SURMOFs; (ii) E-jet printing for high-resolution functional deposits; and (iii) textile devices and washability standards. We benchmark conductivity of IL-integrated MOFs (e.g., IL@HKUST-1 SURMOF ≈ 3–50 μS m-1) against IL@Cu3(HHTP)2 on textile (≈ 1923 μS m-1), clarifying when ILs enable dual ionic-electronic conduction and when pore blocking limits transport. Finally, we outline engineering guidance (ink rheology, jetting window, interdigitated electrode (IDE) geometry on fabrics, humidity mitigation, and wash testing under ISO 6330 protocols) and map sensor performance targets to occupational exposure limits (e.g., OSHA/NIOSH NO limits). This perspective translates recent advances in IL-cMOF textiles into actionable methods for robust, washable, room-temperature NOx badges.