Carbon dioxide (CO₂) is an abundant, nontoxic C1 feedstock, and (hetero)aromatic carboxylic acids are crucial structural frameworks and synthetic precursors in organic, materials, and medicinal chemistry. In this study, we present the deposition of a polyoxometalate@copper (SiW₁₂@Cu NP) catalyst on copper foam via a simple electrodeposition method (potential range: 0.6 to −0.8 V; scan rate: 50 mV·s⁻¹) for the electrocatalytic carboxylation of halo-(hetero)aromatic hydrocarbons with CO₂. The composite electrode leverages the synergistic effects of SiW₁₂ (redox stability, Lewis acidity) and Cu nanoparticles (multivalent states, high conductivity), enhancing electron transfer and CO₂ activation. Under mild reaction conditions (room temperature, 1 atm CO₂, and the absence of noble metals), the prepared catalytic system enables direct carboxylation of not only arenes but also electron-deficient (hetero)arenes, such as halopyridines, with CO₂, achieving a target product yield of over 65% in merely 40 min at a current density of 20 mA. Mechanistic studies confirm that the reaction is initiated by substrate electroreduction, followed by CO₂ fixation. This strategy simplifies the modification of drug intermediates, avoids structural damage to sensitive molecules, and optimizes drug properties through post-carboxylation, providing sustainable technical support for innovation in medicinal chemistry.