Porous organic cage membranes for water desalination: a simulation exploration

Kong, Xian; Jiang, Jianwen

doi:10.1039/c7cp02670f

Cited by 27 publications

(36 citation statements)

References 39 publications

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“…The cation and anion rejections of CC3 and CC19 are predicted to be 100% (Fig. 4b and Supplementary Table 3 ), which is consistent with the above experimental results and the previous simulation studies on the crystalline and amorphous membranes of CC3 19 – 21 . Despite its large pore windows, CC5 only showed slight to negligible cation permeation, which is consistent with the experimental observation.…”

Section: Resultssupporting

confidence: 90%

“…Interestingly, the performance of CC1 provides evidence that the POCs may exist as crystalline structures within the lipid bilayer. CC1, despite exhibiting an apparent lack of porosity when in crystalline state 19 , may contain some interconnected networks when the molecules pack in an amorphous fashion 20 . Therefore, some water permeation may be expected if CC1 packs amorphously.…”

Section: Resultsmentioning

confidence: 99%

“…The POCs were modeled by the Optimized Potentials for Liquid Simulations all atom (OPLS-AA) force field 40 . The non-bonded potentials were also incorporated to describe the cage flexibility 19 , 20 . For the POPC lipids, the potential parameters were adopted from the Berger force filed reparametrized by Tieleman et al 41 .…”

Section: Methodsmentioning

confidence: 99%

“…1b, c ) irrespective of the orientation of the POCs. Molecular simulations of water desalination using bulk tetrahedral POC membranes or POCs in lipid bilayer have shown good water permeation and full salt rejection 19 – 21 . Previous studies have also indicated that water molecules can reversibly reside within the cavity of POCs and their 3D pore networks, enhancing protonic conduction as compared to one-dimensional channels 22 , 23 .…”

Section: Introductionmentioning

confidence: 99%

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Porous organic cages as synthetic water channels

et al. 2020

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Nature has protein channels (e.g., aquaporins) that preferentially transport water molecules while rejecting even the smallest hydrated ions. Aspirations to create robust synthetic counterparts have led to the development of a few one-dimensional channels. However, replicating the performance of the protein channels in these synthetic water channels remains a challenge. In addition, the dimensionality of the synthetic water channels also imposes engineering difficulties to align them in membranes. Here we show that zero-dimensional porous organic cages (POCs) with nanoscale pores can effectively reject small cations and anions while allowing fast water permeation (ca. 109 water molecules per second) on the same magnitude as that of aquaporins. Water molecules are found to preferentially flow in single-file, branched chains within the POCs. This work widens the choice of water channel morphologies for water desalination applications.

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Section: Resultssupporting

confidence: 90%

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Porous organic cages as synthetic water channels

et al. 2020

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“…14−16 Furthermore, proof-of-concept molecular simulation studies were reported to examine crystalline and amorphous POCs for water desalination. 17,18 Attributed to their excellent selectivity, POCs have been explored as fillers in polymer membranes for separation. Lively and co-workers blended amorphous scrambled POCs (AS-POCs) with methylated-polyethylenimine (m-PEI) for SO 2 adsorption; the ASPOCs and mPEI were found to form homogeneous composites with improved adsorption kinetics compared to pure mPEI.…”

Section: Introductionmentioning

confidence: 99%

Molecular Simulation Study on Molecularly Mixed Porous Organic Cage/Polymer Composite Membranes for Water Desalination and Solvent Recovery

Wan

Wang

Jiang

2021

ACS Appl. Nano Mater.

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Emerging as a distinct type of molecular cage possessing both intrinsic and extrinsic porosity, porous organic cages (POCs) have been regarded as intriguing nanofillers to produce molecularly mixed composite membranes (MMCMs).Here, we report a molecular simulation study to examine the swelling of three MMCMs in water, methanol, and acetonitrile and then explore their applications for water desalination and solvent recovery. The MMCMs are formed by mixing three POCs (CC1, CC3, and CC17, respectively) with a polymer of intrinsic microporosity (PIM-1). The POC/PIM membranes exhibit the greatest swelling in methanol, followed by acetonitrile and water. It is revealed that the periphery groups on the POCs have different interactions with the polymer and solvent during swelling, which plays a significant role in determining the structures of swollen membranes. Remarkably, water and methanol permeabilities through PIM-1 are enhanced 1−2-fold by all three POCs, while acetonitrile permeability is enhanced 1-fold by CC17. The enhancement is primarily attributed to the large voids formed in swollen membranes during swelling. Within the simulation durations in this study, all three POC/PIM membranes exhibit perfect rejection toward salt (NaCl) and a small solute (paracetamol). Furthermore, the POCs are observed to provide an additional pathway for solvent transport. A majority of water molecules can reside within the POCs for less than 400 ps, while methanol and acetonitrile molecules reside for approximately 1000 and 2000 ps. The residence time of the solvent is unravelled to depend on not only the solvent−cage interaction but also the solvent size and shape. From the bottom up, this comprehensive simulation study provides microscopic insights into the crucial effects of the POCs on the swelling and solvent permeation of POC/PIM membranes, and it facilitates the judicious selection of appropriate POCs to produce highperformance MMCMs for water desalination, solvent recovery, and other industrially important molecular separation.

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Energy–Structure–Function Maps: Cartography for Materials Discovery

Day

Cooper²

2017

Advanced Materials

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bonding motif that dominates the lattice energy of the framework: that is, directional coordination bonds in the case of PCPs and MOFs, or covalent bonds for COFs. The dominance of a particular arrangement of interactions allows families of structurally related or "isoreticular" [4] frameworks to be prepared because the same bonding pattern can be assumed for multiple linkers. Hence, MOFs and COFs have become enormously popular platforms for a wide variety of materials applications, enabled by the relative ease with which one can explore the available "structure-function space." The importance of this transcends specific materials functions, such as porosity: isoreticular assembly is a powerful, generalizable tool to assemble molecular subunits in the solid state. [5] The situation is different for molecular crystals, which lack extended networks of coordination or covalent bonds. Despite much progress in the field of crystal engineering, [6] it is still rather challenging to program the assembly of molecules in crystalline solids. This is because the intermolecular forces that define molecular crystals-van der Waals and electrostatic interactions-are typically weaker and span a smaller energy range. Consequently, the lattice energies of molecular crystals are more evenly composed of various weak interactions and so the structure-directing forces are a more subtle balance than for PCPs, MOFs, and COFs. Strategies to make molecules crystallize more systematically, such as introducing strong hydrogen-bond donors and acceptors, can succeed but this may also introduce synthetic complexity. Moreover, the addition of such groups to create directional molecular building blocks, or "tectons," [7] can profoundly change the nature of the moleculefor example, by affecting its solubility or polarity-in ways that might not be aligned with the intended function. This can also be true for extended frameworks: in some PCPs and MOFs, the metal serves a specific chemical function, for example, as a catalyst, while in others, the metal is mostly there to hold the framework together-it serves no explicit chemical role.The introduction of directional functional groups such as carboxylic acids into organic tectons exemplifies the strategy of purposeful crystal engineering, whether this be in a hydrogenbonded molecular organic framework or in the organic linker of a MOF. Arguably, such intuitive design strategies will be defeated by complexity for molecular crystals, and even "wellbehaved" isoreticular extended frameworks might carry an unacknowledged overhead in terms of incorporating directing Some of the most successful approaches to structural design in materials chemistry have exploited strong directional bonds, whose geometric reliability lends predictability to solid-state assembly. For example, metal-organic frameworks are an important design platform in materials chemistry. By contrast, the structure of molecular crystals is defined by a balance of weaker intermolecular forces, and small changes to the molecular building b...

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Porous organic cage membranes for water desalination: a simulation exploration

Cited by 27 publications

References 39 publications

Porous organic cages as synthetic water channels

Porous organic cages as synthetic water channels

Molecular Simulation Study on Molecularly Mixed Porous Organic Cage/Polymer Composite Membranes for Water Desalination and Solvent Recovery

Energy–Structure–Function Maps: Cartography for Materials Discovery

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