Layered Nickel–HHTP Networks for Efficient Chemiresistive Sensing of CH 4 and CO 2

ABSTRACT The synthesis and single‐crystal structural elucidation of Ni‐HHTP are reported for the first time, achieved from crystals of sufficient size for electron diffraction analysis. These studies reveal that the crystal structure of Ni‐HHTP alternates between radical‐rich and closed‐shell layers along the c ‐axis, forming a periodic, sandwich‐like architecture. The Ni‐HHTP coordination pattern differs between these two types of alternating 2D‐networks, reflecting distinct electronic environments. Water molecules are either coordinated to the framework or accommodated within the lattice, giving rise to a swelling effect with increasing water content. The well‐defined structure enables direct correlation between framework architecture and function. Ni‐HHTP exhibits a distinct chemiresistive response toward CO 2 and CH 4 —gases of high relevance to greenhouse gas monitoring. Notably, the sensor delivers a clear and measurable response to both gases at concentrations below their ambient atmospheric levels. Theoretical calculations reveal the nature of intramolecular interactions governing the sensing process, providing molecular‐level insight into the chemiresistive behavior of Ni‐HHTP‐based gas sensors.