Hydrophilic microporous lanthanide-organic frameworks based on 4,4 '-biphenyldiacetate: Synthesis, crystal structures and sorption properties

作者：Makhloufi Gamall; Francis Biju; Dechnik Janina; Strzelczyk Alexander; Janiak Christoph^*

来源：Polyhedron, 2017, 127: 59-67.

DOI：10.1016/j.poly.2017.01.038

• Metal-organic frameworks
• MOFs
• Lanthanide organic frameworks
• 4,4 '-Biphenyldiacetic acid
• Gas adsorption

Fifteen microporous coordination polymers of symmetrical and flexible 4,4'-biphenyldiacetate (bpda(2-)) with lanthanide(III) cations (Ln(3+)) of formula {[Ln(2)(bpda)(2)(H2O)]center dot 2H(2)O}(n) (Ln = La (1), Ce (2), Pr (3), Nd (4), Sm (5), Eu (6), Gd (7), Tb (8), Dy (9), Ho (10), Er (11), Tm (12), Yb (13), Lu (14), Y (15)), have been synthesized and characterized. Single crystal X-ray diffraction (for 1, 3 and 4) in combination with powder X-ray diffraction showed isostructural compounds with an infinite secondary building unit (SBU). In this SBU, two crystallographically independent lanthanide ions are connected by three carboxylate groups in chelating-bridging mode to zig-zag Ln-carboxylate chains. These chains are assembled by the biphenyl part of the ligand to a 3D network with water molecules in channels with rectangular cross-sections of similar to 1.6 x 3 angstrom(2). Thermogravimetric analysis indicates complete removal of the water molecules at 150 degrees C and thermal stability up to 380 degrees C. Stability studies on compound 1 show no degeneration in crystallinity after refluxing in water or different organic solvents. The dehydrated compound 1 exhibited no N-2 or H-2 uptake at 77 K and no CH4 or CO2 uptake at 273 K up to 1 bar. High-pressure (17 bar, 273 K) CO2 uptake of dehydrated [Ln(2)(bpda)(3)](n)corresponded to the formation of {[Ln(2)(bpda)(3)]-CO2)(n) with about 40% of the adsorbed CO2 retained upon desorption. Water vapor sorption of activated and hygroscopic [Ln(2)(bpda)(3)]. reformed {[Ln2(bpda)(3)(H2O)]center dot 2H(2)O)(n) 4,4'-Biphenyldiacetic acid (H(2)bpda) shows blue emission, its europium 6 and terbium 8 compounds show red and weak green luminescence under UV light irradiation, with the bpda(2-)ligand acting as an antenna ligand for the europium(III) ions.

• 出版日期2017-5-8