X-ray detection and imaging via scintillators has been utilized in missions worldwide within areas of scientific research, medical industry, military defense and homeland security. Commercial scintillators are costly with high energy consumption through the sintering. It is of great significance to seek alternative scintillating materials for sensitive X-ray detection in the next-generation. Herein, eight structure-defined Ln(III)-based metal–organic frameworks (Ln-MOFs) were prepared, 2D [Ln(1,4-ndc)(DMF)]·nHO (Ln = Sm 1, Eu 2, Dy 3, Tb 4) and 3D [Ln(2,6-ndc)(µ[sbnd]HO)(HO)]·2nHO (Ln = Sm 5, Eu 6, Dy 7, Tb 8), where 1,4-Hndc = 1,4-naphthalene dicarboxylate acid, 2,6-Hndc = 2,6-napthalene dicarboxylate acid, DMF = N,N-dimethylformamide. Merely compounds 2 and 6 show remarkable X-ray scintillation performance via the characteristic red emissions of Eu(III) ions, in which the absorbed energy from the triplet states of the organic moieties can be transferred more efficiently to the resonance emission levels of Eu(III) ions than other lanthanide(III) ions. The X-ray dosage rate detection limits of 2 and 6 are superior to the standard for the medical X-ray diagnosis dosage rate. As proofs-of-concepts, matrix-mixed membranes fabricated with 2 and 6 have achieved remarkable X-ray imaging with high resolution for practical object shooting.