Precisely designed structures inserted in hybrid reactors can be used to control multiphase hydrodynamics and to act as a catalyst carrier simultaneously. While numerical simulations with computational fluid dynamics have limitations regarding the complex interactions in multiphase flows, performing experiments using rapid prototyping (RP) offers the possibility of a fast fabrication and verification of tailor-made structures for specific flow characteristics, efficient mass transport, and high conversion rates. In the presented work, the development of a countercurrently operated additively manufactured reactor for the decarboxylation of ferulic acid to 2-methoxy-4-vinylphenol (MVP) along in situ extraction with n-heptane is shown. Here, the use and optimization of periodic open-cell structures (POCSs) as a carrier for the enzyme phenolic acid decarboxylase and a distributor for the extraction phase are targeted. By RP of transparent structures and their examination concerning the induced flow characteristics of colored heptane, a structure could be optimized for the specific reaction system. The additive manufacturing of POCSs and their application in a hybrid countercurrently operated reactor enabled the conversion of FA and a low concentration of the competitively inhibiting product MVP in the reaction phase via efficient in situ extraction via the dispersed heptane phase.