Imine‐Linked Covalent Organic Cage Porous Crystals for CO₂ Adsorption

Abstract

In this study, covalent organic cages (COC‐MI, COC‐PI and COC‐PA) with covalently imine linked molecules were developed for CO2 adsorption. By varying the organic linkers (iso‐phthalaldehyde to para‐phthalaldehyde) tuned the structure and extrinsic porosity such as specific surface area of the organic cages was demonstrated. Additionally, COC‐PI (3.8 cm3/g to 5.7 cm3/g) and COC‐PA (0.43 cm3/g to 0.48 cm3/g) showed the significantly enhancement in CO2 adsorption capacity with increase in temperature from 273 K to 298 K at 1 bar. On the other hand, COC‐MI (1.17 cm3/g to 1.1 cm3/g) cage showed the significant reduction in CO2 adsorption capacity with increase in temperature from 273 K to 298 K at 1 bar. These unusual enhancements of CO2 adsorption capacity within COC‐PI and COC‐PA is elucidated by powder X‐ray diffraction (PXRD), and it is shown that cooperative diffusion and induced crystal lattice expansion in these molecular crystals can enhance the CO2 adsorption capacity. Computational modelling on the COC cages with CO2 reveals the higher binding energy and rigidity at the C=N group during intermolecular interactions enhances the overall CO2 adsorption capacity in the bulk.

PEEK–WC-Based Mixed Matrix Membranes Containing Polyimine Cages for Gas Separation

“…Assuming a density of approx. 0.5 g cm −3 for the cages [ 29 ] and 1.249 g cm −3 for the PEEK-WC [ 43 ], the volume fraction of the cages is 38.4% in the MMMs with 20 wt % of cages, and (4) and (5) predict that their permeability falls in the interval 0.517 P c < P MMM < 2.87 P c . In practice, the decrease for many gases in the m -xy-based MMM is close to or even slightly larger than predicted by (5), suggesting that we deal with almost impermeable fillers or that the fillers also affect the bulk properties of the polymer.…”

“…These features, which are also maintained after reduction to the amino form, are employed by several groups to enhance the cage selectivity towards guest molecules in solution. A number of bistren azacryptands (in particular polyimine systems) has also been reported as solid materials for the electrochemical reduction of CO 2 to CO and for CO 2 sequestration processes from multicomponent gas streams [ 29 , 30 , 31 ]. However, as far as we know, this particular class of molecules has never been tested in MMMs.…”

Recent Advances in Tris‐Primary Amine Based Organic Imine Cages and Related Amine Macrocycles

“…Jaya Prakash and co‐workers disclosed some worthwhile features of three cages 87 , 88 , and 89 (Figure 5). [ 46 ] Several spectroscopic analyses along with SEM have been considered to characterize the structure and morphology of the cages. Among these three, 88 provided better adsorption capability toward CO 2 over the others though none of them retained CO 2 gas molecules at low pressure.…”

CO2 Separation by Imide/Imine Organic Cages

“…The most common POCs are probably the systems obtained by imine condensation between suitably designed polyaldehydes and polyamines [9,32,33] . The [4+6] imine cages reported by Mastalerz et al., [8] for instance, display porosity features that are comparable to those achieved with some covalent organic frameworks.…”