Anionic Lanthanide MOFs as a Platform for Iron-Selective Sensing, Systematic Color Tuning, and Efficient Nanoparticle Catalysis

New porous anionic Ln-MOFs, namely, [Me 2 ­NH 2 ]­[Ln­(CPA) 2 ­(H 2 O) 2 ] (Ln = Eu, Gd), have been prepared through the self-assembly of 5-(4-carboxy phenyl)­picolinic acid (H2CPA) and lanthanide ions. They feature open anionic frameworks with 1-D hydrophilic channels and exchangeable dimethylamine ions. The Eu phase could detect Fe3+ ions with high selectivity and sensitivity in either aqueous solution or biological condition. The ratios of lanthanide ions on this structure platform could be rationally tuned to not only achieve dichromatic emission colors with linear correlation but also attain three primary colors (RGB) and even white light with favorable correlated color temperature. Furthermore, the Ag­(I)-exchanged phases can be readily reduced to afford Ag nanoparticles. The as-prepared Ag@­Ln-MOFs composite shows highly efficient catalytic performance for the reduction of 4-nitrophenol.