Scalable frequency selective microwave-assisted reactor setup for organic synthesis

In this study, a novel scalable microwave-assisted reactor setup is introduced that combines four Complementary Split Ring Resonators (CSRRs) operating at multiple frequencies (2, 4, 6, and 8 GHz) with a microfluidic cell, achieving high-temperature uniformity and precise in-situ temperature measurements for microwave-assisted organic synthesis. The reactor achieves high-temperature uniformity according to both COMSOL simulations and temperature measurements validated using the temperature-dependent fluorescent dye Rhodamine B. Precise in-situ temperature readings are obtained using a single temperature sensor located in the center of the microfluidic reactor. Four heaters were characterized using both polar and non-polar solvents, showing a maximum heating rate of 153 °C/s with a 5 W incident microwave (MW) heating power. Finally, the scalability of the proposed setup was investigated using a power divider and a MW Single Pole, Double Throw (SPDT) switch with reactors operating at the same and various frequencies for a multistep synthesis or double the throughput. The two scalability options are compared in terms of the applied power and the ability to reach distinct temperatures for the reactors working at the same or various frequencies. These findings highlight the potential of the proposed approach to overcome scalability and precise temperature measurement challenges associated with planar MW heaters and advance the efficiency and repeatability of chemical synthesis. © 2025 Elsevier B.V., All rights reserved.