Two-Dimensional Charge-Separated Metal–Organic Framework for Hysteretic and Modulated Sorption

A charge-separated
metal–organic framework (MOF) has been successfully synthesized
from an imidazolium tricarboxylate ligand, N-(3,5-dicarboxylphenyl)-N′-(4-carboxylbenzyl)­imidazolium chloride (DCPCBImH3Cl), and a zinc­(II) dimeric secondary building unit, namely, DCPCBim-MOF-Zn, which shows an unprecedented 3,6-connected
two-dimensional net topology with the point (Schläfli) symbol
(42.6)2(44.69.82). The framework contains one-dimensional highly polar channels,
and density functional theory calculations show that positive charges
are located on the imidazolium/phenyl rings and negative charges on
the carboxylate moieties. The charge-separated nature of the pore
surface has a profound effect in their adsorption behavior, resulting
in remarkable hysteretic sorption of various gases and vapors. For
CO2, the hysteretic sorption was observed to occur even
up to 298 K. Additionally, trace chloride anions present in the pore
channels are able to modulate the gas-sorption behavior.