Macroporous ZnO Nanoreactors Decorated with Amorphous CoO_<i>x</i> Clusters for Room Temperature Sensors of Acetone in Breath

Although breath analysis holds significant promise for noninvasive disease diagnosis, metal-oxide acetone sensors still face major challenges, including the need for elevated operating temperatures, severe humidity interference, and limited selectivity. Here, we report a three-dimensional ordered macroporous amorphous Co5%Ox/ZnO (3DOM-Co5%Ox/ZnO) hierarchical architecture fabricated via a multiscale structural codesign strategy to enable highly sensitive and selective room-temperature acetone detection. By integrating a metal–organic framework (MOF) templating approach with precise pyrolysis control, we achieved uniform dispersion of amorphous Co5%Ox clusters and formation of an interconnected macroporous–mesoporous network featuring abundant oxygen vacancies and Co2+ Lewis-acid sites. This unique structure confers three synergistic advantages: (i) hierarchical channels overcome Knudsen diffusion limits to accelerate gas transport; (ii) the dual-site recognition mechanism, involving both oxygen vacancies and Co2+ centers, enables selective adsorption of acetone molecules; and (iii) Co5%Ox clusters facilitate interfacial charge transfer, reducing activation energy for acetone oxidation. As a result, the 3DOM-Co5%Ox/ZnO sensor exhibits a response of 7.2 toward 0.5 ppm acetone at room temperature, a detection limit of 10.6 ppb, and retains over 90% of its sensitivity at 75% relative humidity (RH). Moreover, selectivity against isopropanol and other common interferents is enhanced 8-fold. Simulated breath tests with healthy and acetone-spiked samples confirm the sensor’s ability to distinguish diabetic-level acetone concentrations from normal exhalations. This design enables unprecedented performance for noninvasive breath acetone analysis, overcoming key limitations of conventional metal oxide sensors, such as the need for elevated operating temperatures and poor selectivity under humid conditions. This work establishes a materials paradigm for next-generation, noninvasive breath-based diagnostic devices.