One of the most important environmental challenges of modern society is to develop new catalysts that make possible chemical processes with reduced environmental impact. Catalyst immobilization is an appealing strategy that, in addition to facilitating catalyst recovery, has proved to give higher catalytic performance, since the solid support usually provides chemical, thermal, and mechanical stabilization to the catalytic species. In this work Cu/Al2O3 catalytic system with a woodpile porous structure is synthesized by 3D printing and then sintered at high temperature to generate a copper-supported rigid structure with high mechanical strength, a high surface-to-volume ratio, and controlled porosity. The catalytic species (Cu) are immobilized in the Al2O3 matrix to avoid the leaching of the metal into the reaction medium. Al2O3 was selected because it is a good material to obtain a structure with high mechanical stability after high-temperature treatment. The resulting device shows high catalytic efficacy and good recyclability and did not produce leaching of copper to the reaction medium in different Ullmann reactions. Ease of preparation, excellent reactivity, recyclability, and negligible metal contamination all make the 3D printing technique a good strategy for fabricating other types of metal/oxide heterogeneous catalytic systems.