Stable Lanthanide-Organic Framework as a Luminescent Probe To Detect Both Histidine and Aspartic Acid in Water.

A three-dimensional metal-organic framework (MOF) {[Eu(L)(H2O)2]·DMF} n (1) (H3L = 2'-nitro-3,4',5-biphenyl tricarboxylic acid) was obtained by hydrothermal methods and was characterized in detail. Compound 1 contains [Eu2] binuclear units, and [Eu2] units are further linked by H3L, forming a three-dimensional structure. Stability tests suggest that compound 1 exhibits high solvent, pH, and thermal stability. Besides, we also explored the influence of pH values in the luminescence emission of 1 which shows that pH has a negligible effect on the luminescence intensity with the range of pH = 3-11. Importantly, luminescent investigations reveal that 1 can selectively detect aspartic acid or histidine among 14 amino acids with good regenerability in water. Meanwhile, the concentration of aspartic acid can be quantitatively determined. We also discuss the mechanism of luminescence quenching and enhancement in detail. Importantly, this Eu-MOF provides a MOF-based luminescence sensor to detect two amino acids for the first time.

Wheel-like Ln18 Cluster Organic Frameworks for Magnetic Refrigeration and Conversion of CO2.

Two isostructural 2D MOFs ([Ln7(CDA)6(HCOO)3(µ3-OH)6(H2O)8] n, abbreviated as 1-Gd and 2-Dy) were successfully synthesized under solvothermal conditions. The self-assembly of lanthanide(III) nitrate and 1,1'-cyclopropane-dicarboxylic acid (H2CDA) resulted in wheel-like Ln18 cluster second building units (SBU), which are further linked to six neighboring wheels to generate a 2D ordered honeycomb array. Both 1-Gd and 2-Dy exhibit high thermal stability and decompose above 330 °C. Moreover, they have good solvent stability in ten common solvents and pH stability with pH values from 1 to 13. Magnetic studies reveal that 1-Gd exhibits weak antiferromagnetic coupling between adjacent Gd3+ ions and has a large magnetocaloric effect of 47.30 J kg-1 K-1 (Δ H = 7.0 T at 2 K), while 2-Dy shows ferromagnetic interaction between adjacent Dy3+ ions. Interestingly, 1-Gd and 2-Dy can catalyze the cycloaddition of CO2 to epoxides under mild conditions and can be reused at least five rounds with negligible loss of catalytic performance.