Membranes with high selectivity offer an attractive route to molecular separations, where technologies such as distillation and chromatography are energy intensive. However, it remains challenging to fine tune the structure and porosity in membranes, particularly to separate molecules of similar size. Here, we report a process for producing composite membranes that comprise crystalline porous organic cage films fabricated by interfacial synthesis on a polyacrylonitrile support. These membranes exhibit ultrafast solvent permeance and high rejection of organic dyes with molecular weights over 600 g mol −1 . The crystalline cage film is dynamic, and its pore aperture can be switched in methanol to generate larger pores that provide increased methanol permeance and higher molecular weight cut-offs (1,400 g mol −1 ). By varying the water/methanol ratio, the film can be switched between two phases that have different selectivities, such that a single, ‘smart’ crystalline membrane can perform graded molecular sieving. We exemplify this by separating three organic dyes in a single-stage, single-membrane process.

The dispersion of particulate porous solids in size-excluded liquids has emerged as a method to create Type III porous liquids, mostly using insoluble microporous materials such as metal-organic frameworks (MOFs) and zeolites. Here, we present the first examples of Type III porous liquids based on porous organic cages (POCs). By exploiting the solution processability of the POCs, racemic and quasiracemic cage microparticles were formed by chiral recognition. Dispersion of these porous microparticles in a range of size-excluded liquids, including oils and ionic liquids, formed stable POC-based Type III porous liquids. The flexible pairing between the solid POC particles and a carrier liquid allows the formation of a range of compositions, pore sizes, and other physicochemical properties to suit different applications and operating conditions. For example, we show that it is possible to produce porous liquids with relatively low viscosities (7-14 mpa∙s) or high thermal stability (325 °C). A 12.5 wt. % Type III porous liquid comprising racemic POC microparticles and an ionic liquid, [BPy][NTf2], shows a CO2 working capacity (104.30 μmol/gL) that is significantly higher than the neat ionic liquid (37.27 μmol/gL) between 25 °C and 100 °C. This liquid is colloidally stable and can be recycled at least 10 times without loss of CO2 capacity.

Computation is increasingly being used to try to accelerate the discovery of new materials. One specific example of this is porous molecular materials, specifically porous organic cages, where the porosity of the materials predominantly comes from the internal cavities of the molecules themselves. The computational discovery of novel structures with useful properties is currently hindered by the difficulty in transitioning from a computational prediction to synthetic realisation. Attempts at experimental validation are often time-consuming, expensive and, frequently, the key bottleneck of material discovery. In this work, we developed a computational screening workflow for porous molecules that includes consideration of the synthetic difficulty of material precursors, aimed at easing the transition between computational prediction and experimental realisation. We trained a machine learning model by first collecting data on 12,553 molecules categorised either as `easy-to-synthesise' or `difficult-to-synthesise' by expert chemists with years of experience in organic synthesis. We used an approach to address the class imbalance present in our dataset, producing a binary classifier able to categorise easy-to-synthesise molecules with few false positives. We then used our model during computational screening for porous organic molecules to bias towards precursors whose easier synthesis requirements would make them promising candidates for experimental realisation and material development. We found that even by limiting precursors to those that are easier-to-synthesise, we are still able to identify cages with favourable, and even some rare, properties.

The continuous and scalable synthesis of a porous organic cage (CC3), obtained through a 10-component imine polycondensation between triformylbenzene and a vicinal diamine, was achieved using twin screw extrusion (TSE). Compared to both batch and flow syntheses, the use of TSE enabled the large scale synthesis of CC3 using minimal solvent and in short reaction times, with liquid-assisted grinding (LAG) also promoting window-to-window crystal packing to form a 3-D diamondoid pore network in the solid state. A new kinetically trapped [3+5] product was also observed alongside the formation of the targeted [4+6] cage species. Post-synthetic purification by Soxhlet extraction of the as-extruded ‘technical grade’ mixture of CC3 and [3+5] species rendered the material porous.

Control of pore window size is the standard approach for tuning gas selectivity in porous solids. Here, we present the first example where this is translated into a molecular porous liquid formed from organic cage molecules. Reduction of the cage window size by chemical synthesis switches the selectivity from Xe-selective to CH4-selective, which is understood using 129Xe, 1H, and pulsed-field gradient NMR spectroscopy.

We describe the a priori computational prediction and realization of multi-component cage pots, starting with molecular predictions based on candidate precursors through to crystal structure prediction and synthesis using robotic screening. The molecules were formed by the social self-sorting of a tri-topic aldehyde with both a tri-topic amine and di-topic amine, without using orthogonal reactivity or precursors of the same topicity. Crystal structure prediction suggested a rich polymorphic landscape, where there was an overall preference for chiral recognition to form heterochiral rather than homochiral packings, with heterochiral pairs being more likely to pack window-to-window to form two-component capsules. These crystal packing preferences were then observed in experimental crystal structures.

We report a facile, one-step post-synthetic fluorination method to increase the CO2 capacity and CO2/N2 selectivity of porous organic Scholl-coupled polymers.

Porous organic cages have emerged over the last 10 years as a subclass of functional microporous materials. However, among all of the organic cages reported, large multicomponent organic cages with 20 components or more are still rare. Here, we present an [8 + 12] porous organic imine cage, CC20, which has an apparent surface area up to 1752 m2 g-1, depending on the crystallization and activation conditions. The cage is solvatomorphic and displays distinct geometrical cage structures, caused by crystal-packing effects, in its crystal structures. This indicates that larger cages can display a certain range of shape flexibility in the solid state, while remaining shape persistent and porous.

A hypercrosslinked polymer doped with Ag(i) shows high selectivity toward olefins over paraffins under flowing conditions.

Porous liquids are an emerging class of materials and to date little is known about how to best design their properties. For example, bulky solvents are required that are size-excluded from the pores in the liquid, along with high concentrations of the porous component, but both of these factors may also contribute to higher viscosities, which are undesirable. Hence, the inherent multivariate nature of porous liquids makes them amenable to high-throughput optimisation strategies. Here we develop a high-throughput robotic workflow, encompassing the synthesis, characterisation and property testing of highly-soluble, vertex-disordered porous organic cages dissolved in a range of cavity-excluded solvents. As a result, we identified 29 cage-solvent combinations that combine both higher cage-cavity concentrations and more acceptable carrier solvents than the best previous examples. The most soluble materials gave three times the pore concentration of the best previously reported scrambled cage porous liquid, as demonstrated by increased gas uptake. We were also able to explore alternative methods for gas capture and release, including liberation of the gas by increasing the temperature. We also found that porous liquids can form gels at higher concentrations, trapping the gas in the pores, which could have potential applications in gas storage and transportation.

We show that a [3 + 6] trigonal prismatic imine (a) cage can rearrange stoichiometrically and structurally to form a [6 + 12] cage (b) with a truncated tetrahedral shape. Molecular simulations rationalize why this rearrangement was only observed for the prismatic [3 + 6] cage TCC1 but not for the analogous [3 + 6] cages, TCC2 and TCC3. Solvent was found to be a dominant factor in driving this rearrangement.

ABSTRACTTwo methods of incorporating functional groups rich in nitrogen into low cost microporous hypercrosslinked polymers (HCPs) have been evaluated and the effects on the carbon dioxide CO2/N2 IAST selectivity were measured. Electrostatic incorporation of an ammonium salt into a sulfonic acid‐containing HCP polymer afforded a static CO2 uptake of 2.5 mmol g−1 with a CO2/N2 IAST selectivity of 42:1 at 1 bar and 298 K. Using column breakthrough measurements with a 15:85 CO2/N2 mixture at 298 K and 1 bar, a selectivity of 17:1 was obtained. However, varying the counterion resulted in polymers with lower CO2/N2 selectivity values. Decoration of the parent polymer with CO2‐philic imidazole followed by electrostatic ammonium salt incorporation blocked some of the micropores reducing the selectivity which re‐emphasizes the role and importance of pore width for CO2/N2 selectivity. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 2513–2521

Two dissymmetric racemic analogues of the chiral porous organic cage, CC3, were isolated and unambiguously characterised as a racemate pair of the R,R,R,S,S,S and S,S,S,R,R,R-diastereomers (CC3-RS and CC3SR). CC3-RS/CC3-SR equals the highest porosity measured for CC3 but is an order of magnitude more soluble, making it an excellent candidate for incorporation into a membrane for separation applications.

In this work, we demonstrate that the introduction of pyrene and alkyne groups into a highly conjugated microporous polymer (LKK-CMP-1) can be achieved via oxidative homocoupling of 1,3,6,8-tetraethynylpyrene (L). The 1,3-diyne-linked conjugated microporous polymer not only has good thermal stability but also has small pore sizes. These small pores within LKK-CMP-1 facilitate the interactions between CO2 and its pore walls, evidenced by the high isosteric heats of adsorption of CO2 and also confirmed by ideal-adsorption-solution-theory (LASI) calculations based on single-component-isotherm data. Therefore, despite moderate CO2 adsorption uptake (9.78 wt %, 273 K, and 1 bar) and isosteric heat of adsorption (35.0 kJ mol(-1)) for CO2, LKK-CMP-1 still exhibits excellent selectivities of CO2/N-2 (44.2) and CO2/CH4 (8.2) at molar ratios of 15:85 and 20:80 respectively. In addition, breakthrough experiments have also shown that LKK-CMP-1 is an effective material for CO2/N-2 and CO2/CH4 separations under flowing conditions.

Supramolecular synthesis is a powerful strategy for assembling complex molecules, but to do this by targeted design is challenging. This is because multicomponent assembly reactions have the potential to form a wide variety of products. High-throughput screening can explore a broad synthetic space, but this is inefficient and inelegant when applied blindly. Here we fuse computation with robotic synthesis to create a hybrid discovery workflow for discovering new organic cage molecules, and by extension, other supramolecular systems. A total of 78 precursor combinations were investigated by computation and experiment, leading to 33 cages that were formed cleanly in one-pot syntheses. Comparison of calculations with experimental outcomes across this broad library shows that computation has the power to focus experiments, for example by identifying linkers that are less likely to be reliable for cage formation. Screening also led to the unplanned discovery of a new cage topology-doubly bridged, triply interlocked cage catenanes.

A completely unsymmetrical porous organic cage was synthesized from a C 2v symmetrical building block that was identified by a computational screen. The cage was formed through a 12-fold imine condensation of a tritopic C 2v symmetric trialdehyde with a di-topic C 2 symmetric diamine in a [4+6] reaction. The cage was rigid and microporous, as predicted by the simulations, with an apparent Brunauer-Emmett-Teller surface area of 578 m2 g-1. The reduced symmetry of the tritopic building block relative to its topicity meant there were 36 possible structural isomers of the cage. Experimental characterization suggests a single isomer with 12 unique imine environments, but techniques such as NMR could not conclusively identify the isomer. Computational structural and electronic analysis of the possible isomers was used to identify the most likely candidates, and hence to construct a 3-dimensional model of the amorphous solid. The rational design of unsymmetrical cages using building blocks with reduced symmetry offers new possibilities in controlling the degree of crystallinity, porosity, and solubility, of self-assembled materials.

We report a facile, one-step post-synthetic fluorination method to increase the CO2 capacity and CO2/N2 selectivity of porous organic Scholl-coupled polymers. All of the fluorinated polymers that we synthesised showed increases in CO2/N2 IAST selectivity and CO2 isosteric heat; almost all materials also showed an increase in absolute CO2 uptake. Our best-performing material (SC-TPB F) demonstrated a CO2 capacity and CO2/N2 selectivity of 3.0 mmol g 1 and 26 : 1, respectively, at 298 K—much higher than the corresponding non-fluorinated polymer, SC-TPB. This methodology might also be applicable to other polymer classes, such as polymers of intrinsic microporosity, thus providing a more general route to improvements in CO2 capacity and selectivity.

Hypercrosslinked polymers (HCPs) are an important class of porous materials that can be synthesized from aromatic precursors using a one-step "knitting" procedure. This scalable process allows wide synthetic diversity and ease of functionalization. However, pristine HCPs lack electrical conductivity, which limits their potential for electrochemical applications. Supercapacitors are energy storage devices with advantages over conventional batteries such as high power densities, rapid charge speeds, and superior cyclability. In this work, carbonization of functionalized HCPs yields highly conductive and porous materials that can be used as supercapacitor electrodes. Both electric double-layer capacitance (EDLC) and pseudocapacitance (PC) mechanisms are observed. The relative EDLC and PC contributions were quantified for a range of 20 HCP-derived materials, thus allowing a controlled approach to tuning the energy storage properties. The HCP-based carbons show ideal supercapacitor behavior and the best performing material, which shows 63% PC, displays exceptionally high capacitances of up to 374 F g(-1), excellent capacitance retention at fast charging speeds, and stability for up to 15,000 charge/discharge cycles.