Low selectivity is one of the greatest challenges in the electrocatalytic CO2 reduction reaction (CO2RR), e.g. when using copper-based catalysts in aqueous solution. Here we report on the pure production of acetate (apart from H2) from CO2RR with a novel polymeric Cu ligand (pyridine-N and carbonyl group) complex (p-CuL) core-shell microspheres, synthesized by a simple thermal polymerization of urea and Cu-urea complex. The highly selective reduction of CO2 to acetate with no detectable gas products other than H2 is made possible by the unique coordination of pyridinic N and C = O with copper, whose chemical state is between +1 and +2, and the porous 3D core, which is for acetate product kinetically favorable. The maximum Faradiac efficiency of acetate of ~ 64% is reached at -0.37 V vs. RHE in 0.5 M KHCO3 electrolyte, and the evolution of H2 is strongly suppressed. In the process from CO2RR to acetate, the Cu (II) carbonyl coordination is retained, while the active centers of the Cuδ + ligand are reduced to Cu (I). In addition, the highly selective acetate production with p-CuL core-shell microsphere is favored for the adsorption of some important intermediates in CO2 reduction and their dimerization and further e- / h + reduction, such as from the significantly increased C = O and – OH groups in the O K-edge X-ray absorption spectrum (XAS) from p-CuL to CO2RR.