Anhydrous Proton Conduction Through a Chemically Robust Electrolyte Enabling a High-Temperature Non-Precious Metal Catalyzed Fuel Cell.

Fuel cells offer great promise for portable electricity generation, but their use is currently limited by their low durability, excessive operating temperatures, and expensive precious metal electrodes. It is therefore essential to develop fuel cell systems that can perform effectively using more robust electrolyte materials, at reasonable temperatures, with lower-cost electrodes. Recently, proton exchange membrane fuel cells have attracted attention due to their generally favorable chemical stability and quick start-up times. However, in most membrane materials, water is required for proton conduction, severely limiting operational temperatures. Here, for the first time it is demonstrated that when acidified, PAF-1 can conduct protons at high temperatures, via a unique framework diffusion mechanism. It shows that this acidified PAF-1 material can be pressed into pellets with high proton conduction properties even at high temperatures and pellet thickness, highlighting the processibility, and ease of use of this material. Furthermore, a fuel cell is shown with high power density output is possible using a non-precious metal copper electrode. Acid-doped PAF-1 therefore represents a significant step forward in the potential for a broad-purpose fuel cell due to it being cheap, robust, efficient, and easily processible.

Artificial synthesis of covalent triazine frameworks for local structure and property determination.

Here we show an 'artificial synthesis' method for covalent triazine framework (CTF) materials, enabling localised structural features to be incorporated that result directly from the acid-catalysed synthetic protocol that would otherwise not be captured. This advancement will enable prediction and design of new CTF materials with targeted properties.

Rationalising the influence of solvent choice on the porosity of conjugated microporous polymers.

Conjugated microporous polymers (CMPs) synthesised in different solvents give different surface areas dependent on the solvent choice. No one solvent results in a high surface area across a range of different CMP materials. Here, we present an investigation into how the porosity of CMPs is affected by solvent polarity. It is seen that the trends differ depending on the respective monomer dipole moments and whether hydrogen bonding groups are present in the monomers and are able to interact with the respective solvent via hydrogen bonding. It is believed that this methodology could be used to influence future materials design of both structure and synthesis strategy.

High Uptake and Fast Transportation of LiPF6 in a Porous Aromatic Framework for Solid-State Li-Ion Batteries.

Solid-state Li-ion batteries (SSLIBs) have recently attracted substantial attention from scientists for the advantages of better safety performance. However, there are still several key challenges in SSLIBs that need to be addressed, such as low energy density, poor thermal stability or cycle stability, and large interface resistance. This contribution introduces a novel SSLIB with a porous aromatic framework (PAF-1) accommodating LiPF6 that was used as the solid-state electrolyte (SSE) replacing the liquid electrolyte and diaphragm of traditional Li-ion batteries. The charge, discharge capacity, rate performance and cycle stability of the SSLIB were remarkably enhanced.

A 3D Organically Synthesized Porous Carbon Material for Lithium-Ion Batteries.

We report the first organically synthesized sp-sp3 hybridized porous carbon, OSPC-1. This new carbon shows electron conductivity, high porosity, the highest uptake of lithium ions of any carbon material to-date, and the ability to inhibit dangerous lithium dendrite formation. The new carbon exhibits exceptional potential as anode material for lithium-ion batteries (LIBs) with high capacity, excellent rate capability, long cycle life, and potential for improved safety performance.

Modular and predictable assembly of porous organic molecular crystals.

Nanoporous molecular frameworks are important in applications such as separation, storage and catalysis. Empirical rules exist for their assembly but it is still challenging to place and segregate functionality in three-dimensional porous solids in a predictable way. Indeed, recent studies of mixed crystalline frameworks suggest a preference for the statistical distribution of functionalities throughout the pores rather than, for example, the functional group localization found in the reactive sites of enzymes. This is a potential limitation for 'one-pot' chemical syntheses of porous frameworks from simple starting materials. An alternative strategy is to prepare porous solids from synthetically preorganized molecular pores. In principle, functional organic pore modules could be covalently prefabricated and then assembled to produce materials with specific properties. However, this vision of mix-and-match assembly is far from being realized, not least because of the challenge in reliably predicting three-dimensional structures for molecular crystals, which lack the strong directional bonding found in networks. Here we show that highly porous crystalline solids can be produced by mixing different organic cage modules that self-assemble by means of chiral recognition. The structures of the resulting materials can be predicted computationally, allowing in silico materials design strategies. The constituent pore modules are synthesized in high yields on gram scales in a one-step reaction. Assembly of the porous co-crystals is as simple as combining the modules in solution and removing the solvent. In some cases, the chiral recognition between modules can be exploited to produce porous organic nanoparticles. We show that the method is valid for four different cage modules and can in principle be generalized in a computationally predictable manner based on a lock-and-key assembly between modules.

Formation mechanism of ultra porous framework materials.

Understanding the formation mechanism of ultra porous framework materials may lead to insights into strategies for the design and synthesis of novel ultra porous materials or for the increased surface area of known materials. Several potential formation mechanisms have been proposed based on experimental evidence. Here, we assess, via simulation of the network generation process, these mechanisms and have identified key processes by which network interpenetration is minimised and hence surface area is maximised.

Modelling analysis of the structure and porosity of covalent triazine-based frameworks.

Varying degrees of order have been found experimentally for a series of covalent triazine-based frameworks (CTFs) when synthesised under different reaction conditions. Here, we use molecular modelling to discuss the potential origins of this structural order by analysis of the node and strut building blocks. We use a combination of small model structures based on DFT optimised monomer units and more extended simulations using automated structure growth and molecular dynamics to discuss the influence of the strut structure on the local crystallinity of these materials.

Molecular dynamics simulations of gas selectivity in amorphous porous molecular solids.

Some organic cage molecules have structures with protected, internal pore volume that cannot be in-filled, irrespective of the solid-state packing mode: that is, they are intrinsically porous. Amorphous packings can give higher pore volumes than crystalline packings for these materials, but the precise nature of this additional porosity is hard to understand for disordered solids that cannot be characterized by X-ray diffraction. We describe here a computational methodology for generating structural models of amorphous porous organic cages that are consistent with experimental data. Molecular dynamics simulations rationalize the observed gas selectivity in these amorphous solids and lead to insights regarding self-diffusivities, gas diffusion trajectories, and gas hopping mechanisms. These methods might be suitable for the de novo design of new amorphous porous solids for specific applications, where "rigid host" approximations are not applicable.

Photo-Modulating CO2 Uptake of Hypercross-linked Polymers Upcycled from Polystyrene Waste.

Incorporating photo-switches into skeletal structures of microporous materials or as guest molecules yield photo-responsive materials for low-energy CO2 capture but at the expense of lower CO2 uptake. Here, we overcome this limitation by exploiting trans-cis photoisomerization of azobenzene loaded into the micropores of hypercross-linked polymers (HCPs) derived from waste polystyrene. Azobenzene in HCP pores reduced CO2 uptake by 19 %, reaching 37.7 cm3 g-1 , but this loss in CO2 uptake was not only recovered by trans-cis photoisomerization of azobenzene, but also increased by 22 %, reaching 56.9 cm3 g-1 , when compared to as-prepared HCPs. Computational simulations show that this increase in CO2 uptake is due to photo-controlled increments in 10-20 Šmicropore volume, i. e., adsorption sites and a photo-reversible positive dipole moment. Irradiating these HCPs with visual-range light reverted CO2 uptake to 33 cm3 g-1 . This shows that it is feasible to recycle waste polystyrene into advanced materials for low-energy carbon capture.

Porous organic cages.

Porous materials are important in a wide range of applications including molecular separations and catalysis. We demonstrate that covalently bonded organic cages can assemble into crystalline microporous materials. The porosity is prefabricated and intrinsic to the molecular cage structure, as opposed to being formed by non-covalent self-assembly of non-porous sub-units. The three-dimensional connectivity between the cage windows is controlled by varying the chemical functionality such that either non-porous or permanently porous assemblies can be produced. Surface areas and gas uptakes for the latter exceed comparable molecular solids. One of the cages can be converted by recrystallization to produce either porous or non-porous polymorphs with apparent Brunauer-Emmett-Teller surface areas of 550 and 23 m2 g(-1), respectively. These results suggest design principles for responsive porous organic solids and for the modular construction of extended materials from prefabricated molecular pores.

High surface area amorphous microporous poly(aryleneethynylene) networks using tetrahedral carbon- and silicon-centred monomers.

Poly(aryleneethynylene) networks prepared from tetrahedral monomers are highly microporous and exhibit apparent Brunauer-Emmett-Teller surface areas of up to 1213 m2 g(-1).

Synthetic control of the pore dimension and surface area in conjugated microporous polymer and copolymer networks.

A series of rigid microporous poly(aryleneethynylene) (PAE) networks was synthesized by Sonogashira-Hagihara coupling chemistry. PAEs with apparent Brunauer-Emmet-Teller surface areas of more than 1000 m(2)/g were produced. The materials were found to have very good chemical and thermal stability and retention of microporosity under a variety of conditions. It was shown that physical properties such as micropore size, surface area, and hydrogen uptake could be controlled in a "quantized" fashion by varying the monomer strut length, as for metal-organic and covalent organic frameworks, even though the networks were amorphous in nature. For the first time, it was demonstrated that these properties can also be fine-tuned in a continuous manner via statistical copolymerization of monomer struts with differing lengths. This provides an unprecedented degree of direct synthetic control over micropore properties in an organic network.

Vesicles from peptidic side-chain polymers synthesized by atom transfer radical polymerization.

Block copolymers can adopt a wide range of morphologies in dilute aqueous solution. There is a significant amount of interest in the use of block copolymer vesicles for a number of applications. We show that a series of oligo(valine) and oligo(phenylalanine) peptides coupled to a methacrylic group can be prepared by conventional peptide coupling techniques. These can be successfully polymerized by atom transfer radical polymerization (ATRP) in hexafluoroisopropanol (HFIP) giving access to poly(ethylene oxide)- b-poly(side-chain peptides). Many of these polymers self-assemble to form vesicles using an organic to aqueous solvent exchange. One example with a divaline hydrophobic block gives a mixture of toroids and vesicles. Circular dichroism demonstrates that secondary structuring is observed in the hydrophobic region of the vesicle walls for the valine side-chain containing polymers.

Anionic silicate organic frameworks constructed from hexacoordinate silicon centres.

Crystalline frameworks composed of hexacoordinate silicon species have thus far only been observed in a few high pressure silicate phases. By implementing reversible Si-O chemistry for the crystallization of covalent organic frameworks, we demonstrate the simple one-pot synthesis of silicate organic frameworks based on octahedral dianionic SiO6 building units. Clear evidence of the hexacoordinate environment around the silicon atoms is given by 29Si nuclear magnetic resonance analysis. Characterization by high-resolution powder X-ray diffraction, density functional theory calculation and analysis of the pair-distribution function showed that those anionic frameworks-M2[Si(C16H10O4)1.5], where M = Li, Na, K and C16H10O4 is 9,10-dimethylanthracene-2,3,6,7-tetraolate-crystallize as two-dimensional hexagonal layers stabilized in a fully eclipsed stacking arrangement with pronounced disorder in the stacking direction. Permanent microporosity with high surface area (up to 1,276 m2 g-1) was evidenced by gas-sorption measurements. The negatively charged backbone balanced with extra-framework cations and the permanent microporosity are characteristics that are shared with zeolites.