Zn2SiO4, Zn2GeO4, and CdAl2O4 possess high electron density in their six-membered-ring nano tunnels, manganese from MnO2 was successfully doped into them, and green or blue phosphors were produced in air. It is nanotunnel A with high electron density that induces active sites for the reduction of Mn-IV. Mn-II is captured and reduced to Mn-II on active sites by seizing two electrons from native defect V-O(X) (V-O(X) + Mn4+ -> V-O + Mn2+). CdB4O7:0.02Mn(2+) was also synthesized from MnO2 or MnCO3 to confirm the role of nanotunnels. Such inorganic crystals with unique nanotunnel structure may bring more amazing performances in the field of materials in the future.