Monolithic and packed-bed reactors featuring immobilized catalysts are well-precedented in continuous flow synthesis but can suffer from adverse pressure drops during use due to their small pore sizes and/or structural changes. Herein, we overcome this challenge with the synthesis of a structurally robust silica-based monolith featuring pore sizes on the millimeter scale. The 3-dimensional solid support structure is constructed from a polystyrene foam-based template and features a functional group handle that can be modified to display a reactive catalyst. Here we functionalize the support with palladium(0) for hydrogenation reactions and a modified proline catalyst for the alpha functionalization of aldehydes. Both reactors showed good activity and excellent catalytic longevity when utilized under continuous flow conditions.