Direct air capture of CO₂– topological analysis of the experimental electron density (QTAIM) of the highly insoluble carbonate salt of a 2,6-pyridine-bis(iminoguanidine), (PyBIGH₂)(CO₃)(H₂O)₄

Abstract

Low-temperature X-ray and neutron diffraction experiments are used to characterize the electron-density distribution and intermolecular interactions in the insoluble carbonate salt of a 2,6-pyridine-bis(iminoguanidine), a potential CO2 sequestering agent. The importance of the hydrogen-bonding ability of the cation to the anion–water structure is discussed.

Dialing in Direct Air Capture of CO2 by Crystal Engineering of Bisiminoguanidines

“…The Figure 2). Conformational planarity, π-stacking, and inclusion of hydrogen-bonded water clusters had been generally correlated with low aqueous solubilities of BIG crystals; [24][25][26][27] GBIG clearly conforms to this general rule.…”

“…Conformational planarity, π-stacking, and anion-water clusters are structural features that have been found to impart low aqueous solubilities to this class of crystals. [23][24][25][26][27] As a result, the carbonate salts of PyBIG, DABIG, and MGBIG are less soluble than the corresponding neutral ligands by factors of 8, 38, and 72, respectively, enough to drive the DAC reactions according to Equation 1. In direct contrast, GBIG is the only BIG that forms a bicarbonate rather than a carbonate salt upon reaction with CO 2 .…”

“…[20][21][22][23] The CO 2 absorption from air is driven by the extremely low aqueous solubilities of the BIG carbonate salts (on a par with CaCO 3 ), which can be attributed to a large extent to the strong hydrogen bonds involving the carbonate and guanidinium ions, as well as the water molecules included in the crystals. [24] BIGs are a class of anion-coordinating ligands readily accessible by imine condensation of dialdehydes with aminoguanidinium salts. [25][26][27][28][29] However, to date, only one crystalline BIG system, 2,6-pyridinebis(iminoguanidine), or Py-BIG, has been found effective for DAC.…”

Direct Air Capture of CO2 with Aqueous Amino Acids and Solid Bis-iminoguanidines (BIGs)

“…Following the proof of principle with PyBIG [23][24][25], we now seek to establish the generality of the amino acid/BIG approach to DAC. One advantage of the BIG family of compounds is that their syntheses are straightforward and modular, consisting of imine condensation of aminoguanidinium salts with different dialdehydes [28,29].…”

Crystal engineering in all its hues in IUCrJ

“…For comparison, about 150 papers in the crystal engineering area have been published since the inception of the journal itself. Recent papers that have been published in IUCrJ cover a variety of frontier topics and some representative papers are listed below (Alex et al, 2019;Brink & Helliwell, 2019;Broadhurst et al, 2020;Fatima et al, 2020;Gianopoulos et al, 2019;Oburn et al, 2019;Ranjan et al, 2020). These cover areas like charge density, polymorphism and isomorphism, mechanical properties, pharmaceutical solids, and core papers on supramolecular synthons and synthetic strategy.…”