A series of lanthanide metal‐organic frameworks (Ln‐MOFs) are synthesized through solvothermal conditions with 1,3‐bis(4‐carboxyphenyl)imidazolium (H2L). Owing to the lanthanide contraction effect, two different types of Ln‐MOFs, namely, {Ln(L)2(OH)·3H2O}n (Ln:Pr, Nd, Sm) and {Ln(L)2(COO)(H2O)2·H2O}n (Ln: Eu, Gd, Tb, Dy, Tm, Yb, Y), and their corresponding codoped Ln‐MOFs EuxTb1‐xL are obtained. With careful adjustment of the relative concentration of the lanthanide ions and the excitation wavelength, the color of the luminescence can be systematically modulated and white light emission can be further successfully achieved. Furthermore, by virtue of the temperature‐dependent luminescent behavior, Eu0.2Tb0.8L allows for the design of a thermometer with an excellent linear response to temperature over a wide range, from 40 to 300 K. This work highlights the practical applications of Ln‐MOFs for tailoring fluorescent color and even obtaining practical white light emission, and especially for sensing temperature as luminescent thermometers in a single framework by controlling in different ways. Codoped Ln‐metal‐organic frameworks EuxTb1‐xL are synthesized based on the isostructural Ln‐metal‐organic frameworks using lanthanide ion emitters. With careful adjustment of the relative concentration of the lanthanide ions and the excitation wavelength, the emission trajectory can be modulated, allowing white emission. Furthermore, Eu0.2Tb0.8L allows for the design of a thermometer operating over a wide range, from 40 to 300 K.