We describe a novel and intriguing strategy for the construction of efficient heterogeneous catalysts by hypercrosslinking catalyst molecules in a one‐pot Friedel–Crafts alkylation reaction. The new hypercrosslinked polymers (HCPs) as porous solid catalysts exhibit the combined advantages of homogeneous and heterogeneous catalysis, owing to their high surface area, good stability, and tailoring of catalytic centers on the frameworks. Indeed, a new class of metalloporphyrin‐based HCPs were successfully synthesized using modified iron(III) porphyrin complexes as building blocks, and the resulting networks were found to be excellent recyclable heterogeneous catalysts for the hetero‐Diels–Alder reaction of unactivated aldehydes with 1,3‐dienes. Moreover, this new strategy showed wide adaptability, and many kinds of homogeneous‐like solid‐based catalysts with high catalytic performance and excellent recyclability were also constructed. Holey HCPs: Porous solid catalysts were constructed from hypercrosslinking polymers (HCPs), and exhibited the combined advantages of homogeneous and heterogeneous catalysis. New metalloporphyrin‐based polymers were found to be excellent recyclable heterogeneous catalysts for the hetero‐Diels–Alder reaction of unactivated aldehydes with 1,3‐dienes. This strategy demonstrated a wide applicability, and many kinds of homogeneous‐like solid catalysts were constructed.