Metal–Organic Frameworks with Double Channels for Rapid and Reversible Adsorption of 1,2-Ethylenediamine and Gases

Selective liquid and gas adsorptions are important for
environmental
control and industrial processes. Here, unique porous lanthanide–organic
frameworks of [Ln2(1,3-pdta)2(H2O)2]n2n– {Ln = La (1), Ce (2), Pr (3), and Nd (4), 1,3-pdta = CH2[CH2N­(CH2CO2H)2]2} are template-synthesized
by 1,2-ethylenediamine and fully characterized, which possess hydrophobic
and hydrophilic open channels simultaneously. The skeletons are stable
up to 200 °C. Obvious downfield shifts have been observed for
1,2-ethylenediamine in the confined channel with solid-state 13C NMR measurement. The ammonium salt is directly used for
the removal of 1,2-ethylenediamine in water. Its saturated adsorption
capacity is reached in <1 min and can be regenerated easily with
a similar uptake capacity. Moreover, the materials can also selectively
adsorb O2, CH4, and CO2, respectively,
which is useful for CO2/CH4, CO2/H2, and O2/N2 separation. The combined
hydrophobic and hydrophilic open channels of the lanthanides make
them promising functional materials for the elimination of 1,2-ethylenediamine
and gas separations.