Preparation of chemically uniform and monodisperse microparticles as highly efficient solid acid catalysts for aldol condensation

Abstract

Highly active heterogeneous catalysts are in high demand, but realizing an efficient heterogeneous catalyst with uniform active sites remains challenging. In this study, we present a facile preparation of carboxylic acid-incorporated monodisperse microparticles (COOH-MPs) with uniform active sites and their successful application as an efficient solid acid catalyst for aldol condensation. The micromolding integrated with UV-induced photopolymerization enables one-step preparation of COOH-MPs without any further purification or treatment. The successful fluorescent labeling of the COOH-MPs achieved by EDC/NHS (1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC)/n-hydroxysuccinimide (NHS)) chemistry proves that carboxylic acids are uniformly incorporated throughout the COOH-MPs. The microparticle as a solid acid catalyst is applied for aldol condensation and the catalytic performance is compared with that of conventional inorganic solid acid catalysts. The selectivity for jasminaldehyde over the COOH-MPs is higher than that of conventional catalysts, zeolite H-beta (HBEA with different SiO2/Al2O3 ratios). Overall, the results clearly indicate the potential of this new class of chemically uniform and monodisperse microparticle-based solid acid catalysts for aldol condensation. This approach is highly promising for the application to preparations of various solid catalysts due to its reproducibility, tunability and simplicity.