Application of Microdroplets in Chemical Synthesis

Abstract

Over the course of the past decade, microdroplet chemistry has rapidly evolved into a transformative field, offering unprecedented opportunities in chemical synthesis by leveraging the distinctive physicochemical properties of gas–liquid interfaces. Water-containing microdroplets exploit unique physicochemical characteristics at the gas-liquid interface, including intense interfacial electric fields, localized concentration effects, partial solvation and droplet evaporation, which collectively enable spontaneous chemical reactions and extraordinary reaction acceleration, achieving rate enhancements of several orders of magnitude compared to conventional bulk-phase systems. The confined microenvironment of microdroplets not only enhances mass transfer and molecular collision frequencies but also stabilizes reactive intermediates, facilitating reaction pathways that are otherwise kinetically or thermodynamically constrained. This review begins with a summary of key methods for microdroplet generation, including electrospray ionization, gas nebulization, ultrasonic atomization, levitation techniques, and adiabatic expansion, highlighting how these techniques influence the key characteristics and reactivity of microdroplets. The discussion then advances to the application of these unique properties of microdroplets in diverse chemical synthesis reactions, including redox chemistry, coupling reactions, abiotic synthesis of biomolecules and quasi-electrochemical reactions. The enhanced reaction performance observed in these systems stems from the synergistic contributions of enhanced mass transfer, localized concentration enrichment, interfacial electric fields, and droplet evaporation. Furthermore, the ability of microdroplets to stabilize reactive intermediates under mild conditions enables green synthesis approaches, significantly reducing the reliance on hazardous reagents, metal catalysts, and energy-intensive processes. Despite their enormous potential, microdroplets continue to face challenges related to scalability and process control. Ongoing advances in reactor design, thin-film deposition, solvent recycling, and computational modeling are steadily addressing these limitations. By bridging fundamental research with practical applications, microdroplets chemistry presents its unique value for green synthesis and sustainable chemical production, offering innovative solutions to global challenges across chemistry and related disciplines.

Over the past decade, microdroplet chemistry has rapidly developed in both fundamental properties and applications. In 2011, Cooks et al. first proposed the accelerated reaction characteristics of water microdroplets, laying the foundation for subsequent research.^[1] In the same year, Banerjee and co-workers reported unusual chemical transformations in electrosprayed droplets that are unattainable in the bulk phase, thereby highlighting the concept of the microdroplet as a “tiny reaction vessel.”^[2] In 2015, Zare's group first achieved the syntheses of isoquinoline and substituted quinolines under ambient conditions by leveraging the properties of microdroplets, providing a novel strategy of "tiny reaction vessels" for organic synthesis.^[3] In 2018, this group demonstrated that high electric fields and gas-liquid interfacial effects of microdroplets could significantly accelerate chemical reactions, and in the following year, they reported the spontaneous generation of H₂O₂ in water microdroplets.^[4-5] In 2020, the research teams led by Zare and Min Wei collaborated to determine that the electric field strength at the water microdroplets interface is on the order of 10⁹ V/m.^[6] In 2022, Zhang et al. experimentally captured free electrons and hydroxyl radicals on the interface of microdroplets, providing direct evidence for the interfacial effects in microdroplet chemistry.^[7] In the same year, the team of Teresa Head-Gordon computationally determined that the electric field on water microdroplet interfaces follows a Lorentzian distribution, averaging 1.6 × 10⁹ V/m.^[8] In 2024, Fan and coworkers integrated microdroplets with electrochemistry, employing them as microreactors to facilitate electrochemical reactions.^[9] In 2025, Zhang et al. further advanced the scale-up of microdroplets reactors, steadily propelling microdroplet technology toward industrial implementation.^[10]

Keywords

Microdroplets / Gas-liquid interfacial / Redox chemistry / Reaction acceleration / Reactive intermediates / Green synthesis / Interfacial electric field / Partial solvation

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2026 SIOC, CAS, Shanghai, & WILEY-VCH GmbH