Utilization of Microdroplet-Induced Spontaneous Redox Reactions during the Breath Figure Process for the Functionalization of Porous Material

Micrometer-sized water droplets have emerged as a promising platform to perform spontaneous redox reactions. Nevertheless, explorations concerning the utilization of microdroplet chemistry for material fabrication are rather limited. In the current study, the classic breath figure process was utilized to conduct a microdroplet-induced reduction and oxidation reaction to achieve the functionalization of the porous film. The conversions of AgNO₃ to Ag, resazurin to resorufin, and 4-chloro-2-hydroxybenzaldehyde to 4-chlorocatechol were successfully fulfilled by simply introducing the reactant into the breath figure (BF) process via either atmospheric spraying or direct addition to the casting solution. Both spontaneous reduction and oxidation reactions were proven to take place, induced by the formation of condensed water droplets. The yield of the reduction product can be dynamically manipulated by tuning different experimental conditions, reaching a maximum Ag content of 547 mg/kg. The obtained porous polymeric film decorated with Ag nanoparticles was used effectively as a catalytic substrate for the degradation of methylene blue (MB), resulting in the decrease of the absorption peak of MB from 2.355 to 0.294.