Tetrameric self-assembling of water-lean solvents enables carbamate anhydride-based CO2 capture chemistry.

Carbon capture, utilization and storage is a key yet cost-intensive technology for the fight against climate change. Single-component water-lean solvents have emerged as promising materials for post-combustion CO2 capture, but little is known regarding their mechanism of action. Here we present a combined experimental and modelling study of single-component water-lean solvents, and we find that CO2 capture is accompanied by the self-assembly of reverse-micelle-like tetrameric clusters in solution. This spontaneous aggregation leads to stepwise cooperative capture phenomena with highly contrasting mechanistic and thermodynamic features. The emergence of well-defined supramolecular architectures displaying a hydrogen-bonded internal core, reminiscent of enzymatic active sites, enables the formation of CO2-containing molecular species such as carbamic acid, carbamic anhydride and alkoxy carbamic anhydrides. This system extends the scope of adducts and mechanisms observed during carbon capture. It opens the way to materials with a higher CO2 storage capacity and provides a means for carbamates to potentially act as initiators for future oligomerization or polymerization of CO2.

Single crystal formation in core-shell capsules.

This work extends the scope of microfluidic-based crystallization methods by introducing solid microcapsules. Hundreds of perfectly similar microcapsules were generated per second, allowing a fast screening of crystallization conditions. XRD analyses were performed directly on encapsulated single crystals demonstrating the potential of this process for the characterization of compounds, including screening polymorphism.

Simultaneous CO2 capture and metal purification from waste streams using triple-level dynamic combinatorial chemistry.

A reduction in CO2 emissions is required to mitigate global warming. Post-combustion carbon capture is one of the most developed technologies that has the potential to meet this goal, but its cost prevents its widespread use. A different approach would be to use CO2 directly as it is captured, before it is stored. Here we explore spontaneous CO2 fixation by industrial polyamines as a strategy to generate dynamic libraries of ligands for metal separation and recovery. We identify the CO2 loadings and solvents promoting the optimal precipitation of each metal from the dynamic libraries of complexes. We demonstrate the separation of lanthanum and nickel using the exhaust gas of an internal combustion engine vehicle, and show that the three metal constituents of the La2Ni9Co alloys used to manufacture the batteries of electric vehicles can be separated and recovered by successive CO2-induced selective precipitations. Beyond the concept of CO2-sourced multi-level dynamic coordination chemistry, this study provides a potential framework for integrated CO2 capture and use through sustainable processes.

The dark side of disulfide-based dynamic combinatorial chemistry.

During the last two decades, disulfide-based dynamic combinatorial chemistry has been extensively used in the field of molecular recognition to deliver artificial receptors for molecules of biological interest. Commonly, the nature of library members and their relative amounts are provided from HPLC-MS analysis of the libraries, allowing the identification of potential binders for a target (bio)molecule. By re-investigating dynamic combinatorial libraries generated from a simple 2,5-dicarboxy-1,4-dithiophenol building block in water, we herein demonstrated that multiple analytical tools were actually necessary in order to comprehensively describe the libraries in terms of size, stereochemistry, affinity, selectivity, and finally to get a true grasp on the different phenomena at work within dynamic combinatorial systems.

Wetting the lock and key enthalpically favours polyelectrolyte binding.

By using a combination of readily accessible experimental and computational experiments in water, we explored the factors governing the association between polyanionic dyn[4]arene and a series of α,ω-alkyldiammonium ions of increasing chain length. We found that the lock-and-key concept based on the best match between the apolar and polar regions of the molecular partners failed to explain the observed selectivities. Instead, the dissection of the energetic and structural contributions demonstrated that the binding events were actually guided by two crucial solvent-related phenomena as the chain length of the guest increases: the expected decrease of the enthalpic cost of guest desolvation and the unexpected increase of the favourable enthalpy of complex solvation. By bringing to light the decisive enthalpic impact of complex solvation during the binding of polyelectrolytes by inclusion, this study may provide a missing piece to a puzzle that one day could display the global picture of molecular recognition in water.

Diastereoselective Synthesis of a Dyn[3]arene with Distinct Binding Behaviors toward Linear Biogenic Polyamines.

The extension of the family of dyn[ n]arenes toward a three-membered macrocycle is reported. Through a templated approach, a single diastereoisomer of a dyn[3]arene that bears six carboxyl groups could be isolated by precipitation in 59-63% yield and excellent purity (≥95%). A combination of experimental and computational experiments in water at physiological pH revealed that the macrocycle could bind parent biogenic polyamines with a unique diversity of surface-binding modes. Whereas no binding event could be accurately measured with 1,3-diaminopropane, spermidine formed a classical stoichiometric complex with the dyn[3]arene in the millimolar concentration range. On the other hand, the data obtained for spermine could only be attributed to a more complex binding event with the formation of a 2:1 complex at high [host]/[guest] ratios and redistribution toward a 1:1 complex upon further addition of guest.

Dynamic Covalent Chemistry of Carbon Dioxide: Opportunities to Address Environmental Issues.

Extraction and purification of basic chemicals from complex mixtures has been a persistent issue throughout the development of the chemical sciences. The chemical industry and academic research have grown over the centuries by following a deconstruction-reconstruction approach, reminiscent of the metabolism process. Chemists have designed and optimized extraction, purification, and transformation processes of molecules from natural deposits (fossil fuels, biomass, ores), in order to reassemble them into complex adducts. These highly selective and cost-effective techniques arose from developments in physical chemistry but also in supramolecular chemistry, long before the term was even coined. Thanks to the extremely diverse toolbox currently available to the scientific community, artificial molecular systems of increasing complexity can be built and integrated into high-technology products. If humanity has proven through the ages how gifted it can be at this deconstruction-reconstruction game, which has transformed the natural world to a human-shaped one, it has been confronted for more than a century by a new challenge: the deconstruction and reconstruction from a new type of deposit, the waste resulting from the mass production of disposable manufactured goods. In this Account, we will explore the potential contribution of controlled molecular and supramolecular self-assembly phenomena to the challenge of selective and efficient capture of valuable target molecules from mixtures found in postconsumer waste. While it may appear paradoxical to add more molecular ingredients to an already compositionally complex system in order to address a purification issue, we will compare the selectivity, yield, and cost of such an atypical procedure with traditional physical techniques. In the context of carbon dioxide capture or release, we will specifically focus on the coupling between this reversible covalent fixation of the gas by amines and an additional chemical equilibrium. This equilibrium may involve covalent or noncovalent bond formation between a supplementary species and either the unloaded reactant or the CO2-loaded product. Thereby, this new reactive species may act as a CO2 capture agonist or antagonist by either thermodynamically favoring the carbamation or decarbamation direction. Indeed, superagonism, the increase of CO2 loading per amine site upon carbamation beyond the theoretical limit of 0.5, can be achieved using tightly bound cationic metal counterions. In all cases, upon binding and adduct formation, a mutual selection process occurs between one member of the CO2-based dynamic combinatorial library and one agonist or antagonist, which can itself be contained in a complex mixture of analogues. If this adduct is the only species that, upon formation, can self-aggregate into a separate solid phase, selection and binding are accompanied by translocation, rendering the purification procedure operationally straightforward. This general strategy, based on a simple design of coupled molecular systems, may easily be implemented within new, disruptive technologies for selective extraction of target molecules, thereby providing a substantial environmental and economic benefit.