Interfacial‐Templated Assembly MOF‐on‐MOF Strategy: Engineering of Cu‐HHTP/NUS‐8 for High Performance H ₂ S Sensing

ABSTRACT Hydrogen sulfide (H 2 S) serves as an exhaled‐breath biomarker for conditions such as halitosis and asthma. To address fundamental inefficiencies in charge collection and transport within disordered conductive metal–organic frameworks films, a Cu‐HHTP/NUS‐8 MOF‐on‐MOF structure is constructed. The resulting composite features a uniformly oriented and open nanoarchitecture, which facilitates efficient gas diffusion and exposes interior active sites. The Cu‐HHTP/NUS‐8 chemiresistive sensor shows a 63.4% response to 5 ppm H 2 S at room temperature, with a theoretical limit of detection (LOD) of ∼23 ppb. It retains a strong response under high humidity and only 5.4% decay over 31 days. Integrating it as a floating‐gate in a carbon nanotube field‐effect transistor (CNTFET) further amplifies the detection signal. At V gs = 2.0 V, the device exhibits a 70.5% response to 0.1 ppm H 2 S, with a theoretical LOD of ∼0.71 ppb. This is ∼30.2‐fold better than the chemiresistive mode, with sensitivity rising from 20.74%/ppm to 625.93%/ppm. These results prove interfacial‐templated MOF‐on‐MOF boosts molecular accessibility and charge efficiency, offering a scalable route to high‐performance room‐temperature H 2 S sensors.