A series of lanthanide-based metal-organic frameworks (Ln-MOFs) with significantly improved and tunable upconversion emissions were prepared. Y-MOFs co-doped with Yb3+/Er3+ ions have exhibited characteristic upconversion emissions at 520, 545, and 658 nm under 980 nm laser excitation, the intensities of which vary with Yb3+/Er3+ concentrations. In addition, experimental results have indicated that an excited state absorption mechanism is responsible for the upconversion process of Y-MOF:Yb/Er materials. This study has provided a novel design principle and experimental basis for the preparation of luminescent Ln-MOF materials.