Catalytic reaction active site tends to be the structural defects, such as edges, corners, ribs and other position that has low coordination number. Here, the potassium (K+) type birnessite (i.e. a layered structure MnO2) was designed with different amounts of manganese vacancy (V-Mn) for catalytic oxidation of formaldehyde (HCHO). The content of V-Mn was determined by the ratio of Mn/O and coordination number of Mn-Mn edge-sharing structure. The V-Mn showed a dramatic promotion effect on the activity of birnessite for HCHO oxidation. The specific rate at 30 degrees C over the birnessite with the highest content of V-Mn was highest (0.052 mu mol/m(2) min) under 40 ppm of HCHO, 120,000 mL/g h of GHSV and similar to 80% of relative humidity. The presence of V-Mn induced unsaturated oxygen species and K+ locating nearby V-Mn sites for charge balance facilitated the formation of active oxygen species, accordingly the activity for HCHO oxidation was greatly improved. This finding reveals a way to enhance the catalytic activity of metal oxides via adjusting metal vacancies. (C) 2016 Elsevier B.V. All rights reserved.