Robust Chemiresistive Behavior in Conductive Polymer/MOF Composites

TL;DR

This paper introduces a hybrid material combining conductive MOFs and polymers that significantly improves gas sensor recovery, stability, and range at room temperature through mechanistic insights and material engineering.

Contribution

The study presents a novel hybridization strategy of cMOFs and cPs, enhancing chemiresistive sensor performance and providing a mechanistic understanding of energy band effects and sorbate interactions.

Findings

Enhanced sensor recovery kinetics at room temperature.

Improved cycling stability and dynamic range.

Mechanistic insights linking energy band alignment to sensing performance.

Abstract

Metal-organic frameworks (MOFs) are promising materials for gas sensing but are often limited to single-use detection. We demonstrate a hybridization strategy synergistically deploying conductive MOFs (cMOFs) and conductive polymers (cPs) as two complementary mixed ionic-electronic conductors in high-performing stand-alone chemiresistors. Our work presents significant improvement in i) sensor recovery kinetics, ii) cycling stability, and iii) dynamic range at room temperature. We demonstrate the effect of hybridization across well-studied cMOFs based on 2,3,6,7,10,11-hexahydroxytriphenylene (HHTP) and 2,3,6,7,10,11-hexaiminotripphenylene (HITP) ligands with varied metal nodes (Co, Cu, Ni). We conduct a comprehensive mechanistic study to relate energy band alignments at the heterojunctions between the MOFs and the polymer with sensing thermodynamics and binding kinetics. Our findings reveal that hole enrichment of the cMOF component upon hybridization leads to selective enhancement in desorption kinetics, enabling significantly improved sensor recovery at room temperature, and thus long-term response retention. This mechanism was further supported by density functional theory calculations on sorbate-analyte interactions. We also find that alloying cPs and cMOFs enables facile thin film co-processing and device integration, potentially unlocking the use of these hybrid conductors in diverse electronic applications.