Optical chemical sensors are widely applied in many fields of modern analytical practice, due to their simplicity in preparation and signal acquisition, low costs, and fast response time. Moreover, the construction of most modern optical sensors requires neither wire connections with the detector nor sophisticated and energy-consuming hardware, enabling wireless sensor development for a fast, in-field and online analysis. In this review, the last five years of progress (from 2017 to 2021) in the field of optical chemical sensors development for persistent organic pollutants (POPs) is provided. The operating mechanisms, the transduction principles and the types of sensing materials employed in single selective optical sensors and in multisensory systems are reviewed. The selected examples of optical sensors applications are reported to demonstrate the benefits and drawbacks of optical chemical sensor use for POPs assessment.

5- and 10-oxocorrole species can be readily obtained by reaction of Zn ions with β-octaalkylcorrole.

Chlorogenic acid (CGA) is one of the most common polyphenols found in many fruits, such as coffee cherries, and is among the most economical commodities worldwide. In coffee production, processing and washing require large amounts of water, making wastewater monitoring essential to prevent environmental impact. This work reports the development of a fluorescence‐based hybrid sensor designed for the detection of CGA using water‐soluble porphyrins immobilized on hierarchical LTA zeolite. The system is based on 5,10,15,20‐tetrakis(N‐methyl‐4‐pyridyl)porphyrin (TMPyP) and its Zn(II)‐metallated derivative (ZnTMPyP), synthesized directly on the zeolite surface via ion‐exchange processes. The hybrid materials (LTA/TMPyP and Zn‐LTA/TMPyP) were fully characterized, confirming the preservation of the zeolite structure and the formation of the metalloporphyrin complex within the intercrystalline void network. Fluorescence measurements in phosphate buffer (pH 7.4) showed that Zn‐LTA/TMPyP exhibited the best performance for CGA detection, with a detection limit (LOD) of 0.22 nM. To mitigate potential interference from caffeine and caffeic acid, a novel sensing protocol was implemented using these compounds as a controlled background, maintaining high sensitivity (LOD = 0.64 nmol L ^‐1 ). When tested in real coffee washing water, the sensor quantified CGA at 2.5 ± 0.7 nmol L ^‐1 . The measurement accuracy was validated using a nonlinear standard addition method, yielding a recovery of 96.4%, confirming the sensor's ability to compensate for complex matrix effects. The results show that the Zn‐LTA/TMPyP hybrid material is a highly efficient, stable, and selective platform for CGA monitoring, with strong potential for integration into portable devices for environmental and agro‐industrial applications.

Porphyrinoids have long been utilized as active materials in chemical sensing, leveraging various transduction mechanisms due to their diverse array of properties. We have been particularly interested in the exploitation of porphyrin derivatives for the development of sensor arrays, taking advantage of the synthetic versatility of this macrocycle.