A simple redox method was used to synthesize δ-MnO2 and introduce the first main group metal elements between the layers of δ-MnO2. Through testing, we found that δ-MnO2 doped with Rb+ demonstrated the best catalytic performance for formaldehyde removal. Under the condition of 36 °C and the initial formaldehyde concentration of 200 ppm, a 200 mg of Rb-MnO2 could achieve the percentage of removal of formaldehyde 97.48%. We found that doping elements with low electronegativity and large ion radius could weaken the Mn–O bond, which is conducive to the formation of reactive oxygen species and improve the performance of catalytic oxidation. [ABSTRACT FROM AUTHOR]