A multi-phase catalyst for the simultaneous conversion of oxides of nitrogen, carbon monoxide, and hydrocarbons is provided. A catalyst composition comprising the multi-phase catalyst and methods of making the catalyst composition are also provided. The multi-phase catalyst may be represented by the general formula of CeyLn1-xAx+sMOZ, wherein Ln is a mixture of elements originally in the form of single-phase mixed lanthanides collected from natural ores, a single lanthanide, or a mixture of lanthanides; A is an element selected from a group consisting of Mg, Ca, Sr, Ba, Li, Na, K, Cs, Rb, or any combination thereof; and M is an element selected from the group consisting of Fe, Mn, Cr, Ni, Co, Cu, V, Zr, Pt, Pd, Rh, Ru, Ag, Au, Al, Ga, Mo, W, Ti, or any combination thereof; x is a number defined by 0≦x<1.0; y is a number defined by 0≦y<10; s is a number defined by 0≦s<10; where s=0 only when y>0 and y=0 only when s>0. The multi-phase catalyst can have an overlayer of an oxide having the fluorite structure with a combination of platinum and/or rhodium.