Heterogeneous, metal, single‐site catalysts often exhibit higher catalytic performance than other catalysts because of their maximized atom efficiency of 100 %. Reported herein is a precoordination/solvothermalpolymerization strategy to fabricate a stable mononuclear Pd‐metalized porous organic polymercatalyst (Pd@POP). Pd@POP was easy to use in regioselective organic reactions because the internal structure