Microporous Hexanuclear Ln(III) Cluster-Based Metal–Organic Frameworks: Color Tunability for Barcode Application and Selective Removal of Methylene Blue

Two hexanuclear Ln­(III) cluster-based metal–organic frameworks (MOFs) (Ln = Tb or Eu) and a series of isomorphic bimetallic Ln­(III)-MOFs have been synthesized by changing the ratio of Tb­(III) and Eu­(III) under solvothermal conditions. The excellent linear color tunability (from green to red) makes them suitable for barcode application. In addition, the anionic Ln­(III)-MOFs exhibit superior uptake capacity toward methylene blue (MB⁺) by an ion-exchange process, and its reversible adsorption performance makes 1 suitable for removal of organic dye MB⁺. The as-prepared anionic hexanuclear Ln­(III) cluster-based MOFs can serve as a multifunctional material for an optical and environmental area.