We have designed two metal–organic
frameworks (MOFs) to
efficiently convert X-ray to visible-light luminescence. The MOFs
are constructed from M6(μ3-O)4(μ3-OH)4(carboxylate)12 (M
= Hf or Zr) secondary building units (SBUs) and anthracene-based dicarboxylate
bridging ligands. The high atomic number of Zr and Hf in the SBUs
serves as effective X-ray antenna by absorbing X-ray photons and converting
them to fast electrons through the photoelectric effect. The generated
electrons then excite multiple anthracene-based emitters in the MOF
through inelastic scattering, leading to efficient generation of detectable
photons in the visible spectrum. The MOF materials thus serve as efficient
X-ray scintillators via synergistic X-ray absorption by the metal-cluster
SBUs and optical emission by the bridging ligands.