Περίληψη:
A series of new Zn2+-trimesate (btc(3-)) metal organic frameworks (MOFs)
has been isolated in the presence of various amino-alcohols under
solvothermal conditions. Thus, the reaction of ZnCl2 with trimesic acid
(H(3)btc) and the amino alcohols triethanolamine (teoa),
2(hydroxymethyl)piperidine (hmpip), N-tert-butyldiethanolamine (tbdeoa),
1,4-bis(2-hydroxyethyl)piperazine (bhep), N-methyldiethanolamine
(mdeoa), or 4-(2-hydroxyethyl)morpholine (hem) in a 1.6:1:5.6 molar
ratio in DMF afforded compounds (teoaH)(2)[Zn(btc)(1.33)] (MOAAF-1)
(MOAAF = metal organic amino-alcohol framework),
(NH2Me2)(2)(hmpipH)[Zn-3(btc)(3)] (MOAAF-2),
(NH2Me2)-(tbdmaH)(2)[Zn-3(btc)(3)] (MOAAF-3) (tbdma =
N-tert-butyl-dimethylamine), (NH2Me2)(bhepH(2))[Zn-3(btc)(3)]
(MOAAF-4), (NH2Me2) [Zn-4(btc)(3)(mdeoa)(2)] (MOAAF-5), and
(NH2Me2)[Zn-4(btc)(3)(hem)(2)] (MOAAF-6), respectively. The compounds
display 3D structures with relatively large cavities (4-10 angstrom) and
high potential solvent-accessible areas (38-68% of the unit cell
volumes). A number of novel structural features are revealed in the
reported MOFs, such as unprecedented dinuclear [Zn-2(COO)(5)](-1)
secondary building units (SBUs) and unique network topologies (e.g., in
compounds MOAAF-2, MOAAF-3, MOAAF-5, and MOAAF-6). The amino-alcohols
employed played a key role for the appearance of such novel structural
features in MOAAF 1-6 since they were found to act as bases responsible
for the deprotonation of H(3)btc, templates, and chelating ligands.
Specifically, most of the compounds synthesized were shown to be
templated by protonated amino alcohols that are involved in hydrogen
bonding interactions with the frameworks, whereas in two cases
(compounds MOAAF-5 and MOAAF-6) the amino alcohols acted as chelating
ligands affecting significantly the underline topology of the MOFs. The
thermal stability and photoluminescence properties of the MOFs are also
discussed. This work represents the initial systematic investigation on
the use of combination of amino alcohols and polycarboxylate ligands for
the synthesis of new MOFs, demonstrating it as a powerful synthetic
strategy for the isolation of novel MOFs.
