Upcycling Silicon as Heterogeneous Palladium Catalysts: Heck-Cassar Cross-Coupling in Batch and Flow Conditions

Electronic waste and end-of-life photovoltaic modules are positioning silicon as a high-value material that will increasingly enter the waste stream in the coming years. Strategies to valorize this valuable waste are therefore highly desirable. Among heterogeneous catalysts, SiO₂ plays a prominent role both as a catalyst and as a support for metal nanoparticles. Research activity exploring the use of silicon in catalysis demonstrates different applications in energetic and material chemistry. Given the growing interest in developing materials derived from industrial waste, biomass, and e-waste as supports for heterogeneous catalysts within a circular economy framework, this work aims to demonstrate the effective upcycling of silicon by developing a Pd/Si-based catalytic system. The resulting catalyst is designed for continuous-flow cross-coupling applications, exemplified by the Heck-Cassar reaction, also known as the Cu-free Sonogashira coupling, and demonstrates both robustness and recyclability. Its applicability is demonstrated in the Heck-Cassar reaction across 21 different substrates, with yields ranging from 63% to 99%.