Immobilization strategies for heterogeneous catalysts in micro flow chemistry: Key techniques for efficient and sustainable chemical transformations

In the domain of catalysis, heterogeneous catalysts are predominantly utilized, with catalyst immobilization techniques playing a pivotal role in determining performance and reaction efficiency. A variety of immobilization methods, including in situ growth, hybridization, and chemical grafting, are not only available but also essential for enhancing the number and dispersion of active sites, thereby elevating catalytic efficiency. However, the practical implementation of these techniques often encounters challenges such as reduced reactivity, insufficient stability, and difficulties in maintaining uniformity. Continuous flow heterogeneous catalysis, a significant subset of heterogeneous catalytic systems, has gained prominence in the synthesis of fine chemicals due to its high safety, cost-effectiveness, and efficiency. This review systematically summarizes the current design strategies for heterogeneous catalysts in flow reactors, highlighting the advantages and disadvantages of various immobilization techniques. Specifically, we focus on the successful application of these technologies in microfluidic channels to enhance catalytic activity and selectivity, achieve precise control of reaction conditions, and improve catalyst stability and recyclability. The aim of this review is to provide readers with a deeper understanding of catalyst heterogeneity approaches in microfluidic channels and to facilitate research on the rational design of more advanced heterogeneous catalysts for industrial applications.