Enhancing the activity of surface oxygen species on metal oxides is significant to accelerate sensing process. Modulating electronic spin states of Co 3 + in Co-based oxides is an effective strategy to activate oxygen species. Herein, we present modulating spin states of Co 3+ for Co-based catalysts, featuring strong couple of Co atoms and doping Cu atoms via bridging oxygen. The combined characterizations confirm that electron delocalization induces a reconstruction of the Co Oh 3 d orbitals, leading to high-spin state of Co 3+. The equivalent high-spin ratio of Co Oh reach to 64.8%, triggering the average e g filling of 1.296, which enhance the activity of oxygen species and increased adsorption of reactants. The optimized CuBCO sensor exhibits a high response value of 26.8–20 ppm acetone in comparison of 11.5 for BCO. This work provides a straight forward approach to modulate the spin state of catalysts and elucidate its role in sensing performance.