Crystallisation of calcium carbonate in the presence of the polycarboxylate 1,3-diamino-2-hydroxypropane-N,N,N',N'-tetraacetate results in the formation of "microtrumpets" composed of nanocrystalline calcite.
A new alkaline metal–organic
framework, [Mg3(NDC)3(DMF)4]·H2O (1) is
synthesized solvothermally by using 2,6-naphthalenedicarboxylic acid
(NDC) as ligand and dimethylformamide (DMF) and water as mixed solvent.
Single crystal X-ray studies show that 1 crystallizes
in the space group C2/c with parameters a = 13.4191(2), b = 18.0669(2), c = 20.9746(3) Å, and β = 99.66(0)o. The central
metal atom Mg(II) adopts a six coordinated octahedral geometry with
carboxylate oxygen atoms and DMF molecules. Due to the involvement
of oxygen atoms in bridging and chelation binding, a trinuclear secondary
building unit is built up, which further connects to other six NDC
ligands and finally leading to a three-dimensional network. The thermal
and luminescent analysis revealed that the compound is thermally stable
with violet emission. The creation of coordinatively unsaturated Mg(II)
centers, acting as Lewis-acidic sites upon activation, are explored
to use 1 as heterogeneous catalyst in value-added organic
conversions. MOF showed a superb catalytic performance in the synthesis
of eight 4H-pyran derivatives via one-pot three-component
reaction between aromatic aldehydes, malononitrile, and cyanoacetamide
at room temperature. All the reactions worked exceptionally well with
excellent yields (91–96%), in short reaction times (<40
min). Green solvent (ethanol) and easy separation, reusability and
robust structure of catalyst are the attractions of the protocol and
make [Mg3(NDC)3(DMF)4]·H2O an ideal catalyst for wide-ranging organic transformations.
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