By using Zn(4)O(CO(2))(6) as secondary building units (SBUs) and two extended ligands containing amino functional groups, TATAB and BTATB (TATAB = 4,4',4''-s-triazine-1,3,5-triyltri-p-aminobenzoate and BTATB = 4,4',4''-(benzene-1,3,5-triyltris(azanediyl))tribenzoate), two isostructural mesoporous metal-organic frameworks (MOFs) with cavities up to 2.73 nm, designated as PCN-100 and PCN-101 (PCN represents porous coordination network), have been synthesized. N(2) sorption isotherms of both PCN-100 and -101 showed typical type IV behavior, indicating their mesoporous nature. The TATAB ligand that comprises PCN-100 was employed to capture heavy metal ions (Cd(II) and Hg(II)) by constructing complexes within the pores with a possible coordination mode similar to that found in aminopyridinato complexes. This reveals that mesoporous materials such as PCN-100 can be applied in the elimination of heavy metal ions from waste liquid. In addition, both PCNs-100 and -101 exhibit size-selective catalytic activity toward the Knoevenagel condensation reaction.
A series of 12-connected lanthanide cluster based metal-organic frameworks (MOFs) have been constructed by [Ln(μ-OH)(COO-)] secondary building units (SBUs) and 2-aminobenzenedicarboxylate (BDC-NH) ligands. These obtained materials exhibit high chemical stability and generic thermal stability, especially in acidic and basic conditions. They also present commendable CO adsorption capacity, and Yb-BDC-NH was further confirmed by a breakthrough experiment under both dry and wet conditions. Moreover, these materials possess both Lewis acid and Brønsted base sites that can catalyze one-pot tandem deacetalization-Knoevenagel condensation reactions.
An In III -based anionic framework (In III -MOF) with 4-connected SrAl 2 topology was constructed. The In III -MOF with permanent porosity functions as a host for encapsulation of Ln 3+ ions through ion-exchange processes. The photophysical properties of as-prepared Ln 3+ @In III -MOF were investigated and the results showed that the In III -MOF could serve as an antenna to sensitize Ln 3+ cations, especially suitable for Tb 3+ and Eu 3+ ions. The possible sensitization mechanism has been studied by surface photovoltage spectroscopy. Additionally, In III -MOF could also as host materials applied in the separation and purification of cationic dyes, which is highly based on the size and charge of organic dyes. Moreover, it can be used as chromatographic column stationary phases to separate cationic dyes more efficiently and selectively. It is believed that the as-prepared In III -MOF may provide potential applications in optical materials and environmental fields.
Research progress in lanthanide metal–organic frameworks and their derivatives in the field of catalysis has been presented on the basis of different organic reactions.
Two series of chemically and thermally stable rare-earth MOFs were constructed using trinuclear [M(μ-OH)(COO)] SBUs and linear dicarboxylate linkers, which feature three-dimensional 12-connected frameworks with an hcp topology. These materials contain a large density of Lewis acidic sites, leading to high catalytic activity towards the cycloaddition of CO and epoxides under mild conditions.
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