A new n-type phthalocyanine-based sensor is developed for ultrasensitive and highly selective detection of trace amounts of NO2 against NH3 and H2S.

A metal free meso‐tetrakis(1‐pyrenyl)porphyrin H2T[(Pyr)4]P (1) and its cobalt congener CoT[(Pyr)4]P (2) are firstly fabricated into the hierarchical nanopetals and micro‐ball‐flowers, respectively, by a simple solution‐based method. Unexpectedly highly sensitive, stable, selective and reproducible responses to 50–400 ppb NO2 gas are obtained at room temperature for the aggregates of both 1 and 2, within 2 min dynamic exposure period at a broad relative humidity (RH) range of 0%‐75%. In particular, the micro‐ball‐flowers of 2 achieve a sensitivity of 91.4 and 214% ppm−1 at 45% RH and 75% RH, respectively, demonstrating the potentials as chemical sensors operating in real‐world atmospheres. Furthermore, the sensitivity of 1 and 2 remains almost unchanged under 0%–75% RH after 6 months. The present work represents one of the best results among organic‐based ppb‐level NO2 sensors operating under a broad RH range in terms of sensitivity and stability to humidity variations at room temperature.

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