首页|Confined and synergistic effects between protonated amines and gases in the frameworks of lanthanum 1,3-propanediaminetetraacetates
Confined and synergistic effects between protonated amines and gases in the frameworks of lanthanum 1,3-propanediaminetetraacetates
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NSTL
Lanthanum microporous frameworks (Hdma)_(2n)[La2(1,3-pdta)2(H2O)2]n·5nH2O (1, dma = dimethylamine, 1,3-pdta = 1,3-propanediaminetetraacetic acid) and (H2pn)n[La2(1,3-pdta)2(H2O)2]n·5nH2O (2, pn = 1,3-propane-diamine) with double channels have been template-synthesized by protonated dimethylamines and 1,3-propane-diamines, respectively. While bulky product (H2bn)[La2(1,3-pdta)2(H2O)4]·10H2O (3, bn = 1,4-butanediamine) is isolated as a dinuclear species with tetrahydrates, whose main anion can be served as a precursor for 1 and 2. Materials 1-3 are able to maintain their chemical and thermal stabilities to 200 °C based on TG and XRD analyses. Gas adsorptions demonstrate that MOFs 1 and 2 are amicable for O2 and CO2, while no adsorption has been observed for CH4, N2 or H2 respectively. The amounts of encapsulated CO2 in hydrophobic pores are dependent on the alkalinities of the diamines in the next confined hydrophilic holes, showing synergistic effects between double channels. For protonated dimethylamines and 1,3-propanediamines in 1 and 2, obvious downfield shifts have been found by solid-state ~(13)C NMR spectroscopies, along with clear red shifts in FT-IR spectra compared with free species. Moreover, captured CO2 inside 1 can be quantized by NMR measurements and IR spectroscopies under ambient condition. These all reflect the confinement effects of nano-environments.
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