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)][(CH3)(2)NH2], [Ln = Ho (1), Eu (2), Gd (3), Dy (4), Er (5), Tin (6), Yb (7), Lu (8)], were prepared by 3,3',5,5'-biphenyltetracarboxylic acid (H4BPTC) 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 (Lii,) clusters and feature a one-dimensional curving porous channel occupied by exchangeable dimethylamine cations ([(CH3)(2)NH2](+)) in the 3D anionic frameworks. The occupied ([(CH3)(2)NH2](+)) in the anionic channels exhibited excellent ion-exchange ability, which is favorable to Pd2+ 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 Pdg 1 -8 were higher than that of Pd/C (5 wt %) in the hydrogenation reaction of p-nitrophenol (p-NP). Moreover, Pdgl 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.

Automated summary

In this study, eight new stable porous lanthanide metal-organic frameworks (Ln-OFs) were synthesized and showed excellent ion-exchange and adsorption abilities, making them promising for catalytic reactions and dye adsorption.