Series of Stable Anionic Lanthanide Metal-Organic Frameworks as a Platform for Pollutant Separation and Efficient Nanoparticle Catalysis.

Eight new stable porous lanthanide metal-organic frameworks (Ln-OFs), namely, [Ln 2 (BPTC) 2 ][(CH 3 ) 2 NH 2 ] 2 [Ln = Ho ( 1 ), Eu ( 2 ), Gd ( 3 ), Dy ( 4 ), Er ( 5 ), Tm ( 6 ), Yb ( 7 ), Lu ( 8 )], were prepared by 3,3',5,5'-biphenyltetracarboxylic acid (H 4 BPTC) and lanthanide ions by solvothermal reactions. Complexes 1 - 8 show a three-dimensional (3D) 6,6-connected network {4 12 ·6 3 }·{4 8 ·6 6 ·8} topology based on binuclear (Ln 2 ) clusters and feature a one-dimensional curving porous channel occupied by exchangeable dimethylamine cations ([(CH 3 ) 2 NH 2 ] + ) in the 3D anionic frameworks. The occupied [(CH 3 ) 2 NH 2 ] + in the anionic channels exhibited excellent ion-exchange ability, which is favorable to Pd 2+ and cationic dye adsorption. Consequently, 1 - 8 were used to load Pd nanoparticles to catalyze the reduction of nitrophenols and adsorb and desorb methyl blue (MB). The catalytic reaction efficiencies of Pd@ 1 - 8 were higher than that of Pd/C (5 wt %) in the hydrogenation reaction of p -nitrophenol ( p -NP). Moreover, Pd@ 1 exhibited good cycle stability and achieved nearly 100% p -NP conversion after eight cycles. Meanwhile, compound 1 also exhibited a high adsorption ability of MB, possessing an adsorption capacity of 1.41 g·g -1 (second only to 1.49 g·g -1 reported in the literature) selectively over rhodamine B (RhB) and methyl orange (MO) in aqueous solutions. Remarkably, the skeleton of 1 remained stable after four adsorption-desorption cycles of MB in aqueous solution.