Assembly of Two Porous
Cadmium(II) Frameworks: Selective Adsorption and Luminescent Property
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Abstract
Two microporous cadmium(II) metal–organic frameworks,
[Cd(cptpy)(Ac)(H<sub>2</sub>O)·(DMA)(H<sub>2</sub>O)]<sub><i>n</i></sub> (<b>1</b>) and [Cd(cptpy)<sub>2</sub>·(DMF)<sub>2</sub>]<sub><i>n</i></sub> (<b>2</b>) (Hcptpy =
4-(4-carboxyphenyl)-2,2′:4′,4″-terpyridine, DMA
= <i>N</i>,<i>N</i>-dimethylacetamide, DMF = dimethylformamide)
have been solvothermally synthesized under different reaction conditions.
Complex <b>1</b> is a double-interpenetrating 3D network, while <b>2</b> is a noninterpenetrating (3,5)-connected 2D framework. The
dehydrated forms of compounds <b>1</b> and <b>2</b> exhibit
selective adsorption of CO<sub>2</sub> over N<sub>2</sub> and H<sub>2</sub>O over CH<sub>3</sub>OH. In addition, the adsorption value
of CO<sub>2</sub> for <b>2</b> is higher than that of <b>1.</b> The contents of uncoordinated pyridine nitrogen (Lewis
basic sites) per formula unit of <b>1</b> and <b>2</b> are 2.16 and 4.36%, respectively. Obviously, the grafting of more
uncoordinated pyridine nitrogen into compound <b>2</b> could
enhance adsorption of the acidic CO<sub>2</sub> molecule. Notably,
both <b>1</b> and <b>2</b> display strong photoluminescence.
The nature of electronic transitions for complex <b>1</b> in
the photoluminescent process was investigated by means of time-dependent
density functional theory (TDDFT) calculations and molecular orbital
analyses, which collaborates that the luminescent property is ligand-based
