We propose a simple experimental procedure based on the cloud point measurement of a non-ionic surfactant as a tool for (i) estimating the super-chaotropic behaviour of polyoxometalates (POMs) and for (ii) establishing a classification of POMs according to their affinity towards polar surfaces.

Low charge density nanometric ions were recently shown to bind strongly to neutral hydrated matter in aqueous solution. This phenomenon, called the (super-)chaotropic effect, arises from the partial dehydration of both the nano-ion and the solute, leading to a significant gain in enthalpy. Here, we investigate the chaotropic effect of the polyoxometalate α-PW₁₂O₄₀³⁻ on the triblock copolymer P84: (EO)₁₉(PO)₄₃(EO)₁₉ with (EO)₁₉ the polyethoxylated and (PO)₄₃ the polypropoxylated chains. The combination of phase diagrams, spectroscopic (nuclear magnetic resonance) and scattering (small angle neutron/X-ray scattering) techniques revealed that: (i) below the micellization temperature of P84, PW₁₂O₄₀³⁻ exclusively binds to the propylene oxide moiety of P84 unimers; and (ii) above the micellization temperature, PW₁₂O₄₀³⁻ mostly adsorbs on the ethylene oxide micellar corona. The preferential binding of the PW₁₂O₄₀³⁻ to the PPO chain over the PEO chains suggests that the binding is driven by the chaotropic effect and is reinforced by the hydrophobic effect. At higher temperatures, copolymer micellization leads to the displacement of PW₁₂O₄₀³⁻ from the PPO chain to the PEO chains. This study deepens our understanding of the subtle interplay between the chaotropic and hydrophobic effects in complex salt-organic matter solutions.

In recent years, photoredox chemistry has been intensively investigated due to its sustainability and low energy-cost. Here, we propose a physicochemical concept – called {2-phases 2-reactions 1-catalyst} – to perform two chemical reactions simultaneously with only one catalyst using a liquid–liquid biphasic system. The well-known and commercially available α-Keggin polyoxometalate (POM), PW₁₂O₄₀ ³⁻, was used as a photocatalyst for oxidizing a hydrophobic compound in an organic phase. The reduced POM, PW₁₂O₄₀ ⁴⁻, being more hydrophilic, diffuses then in the aqueous phase where it reduces a hydrophilic compound. After this step, the re-oxidized POM migrates back to the organic phase closing the catalytic cycle. We applied this concept to several basic reactions: oxidations of organic compounds (e.g. alcohol to aldehyde), degradation of organic dyes, metal recovery by reduction of metal ions, and in situ metal–organic complexation reactions. This concept is proposed as a powerful, simple and sustainable tool to couple diverse photo-oxidation/reduction reactions. As an example, oxidative dye degradation/metal (silver) recovery were performed using this general methodology. The main advantage of the {2-phases 2-reactions 1-catalyst} concept is the economy of one reactor and one catalyst, including its self-regeneration by another useful reaction.

Herein, we show how the chaotropic effect arising from reduced molybdate ions in acidified aqueous solution is able to amplify drastically weak supramolecular interactions. Time‐resolved Small Angle X‐ray Scattering (SAXS) analysis suggests that molybdenum‐blue oligomeric species form huge aggregates in the presence of γ‐cyclodextrin (γ‐CD) which results in the fast formation of nanoscopic {Mo ₁₅₄ }‐based host‐guest species, while X‐ray diffraction analysis reveals that the ending‐point of the scenario results in an unprecedented three‐component well‐ordered core–shell‐like motif. A similar arrangement was found by using preformed hexarhenium chalcogenide‐type cluster [Re ₆ Te ₈ (CN) ₆ ] ⁴⁻ as exogenous guest. This seminal work brings better understanding of the self‐assembly processes in general and gives new opportunities for practical applications in the design of complex multicomponent materials via the simplicity of the non‐covalent chemistry.

Low charge density nanometric ions were recently shown to bind strongly to neutral hydrated matter in aqueous solution. This phenomenon, called (super-)chaotropic effect, arises from the partial dehydration of both, the nano-ion and the solute, leading to a high gain in enthalpy. Here, we investigate the chaotropic effect of the polyoxometalate α-PW12O403- on the triblock copolymer P84: (EO)19(PO)43(EO)19 with (EO)19 the polyethoxylated and (PO)43 the polypropoxylated chains. The combination of phase diagrams, spectroscopic (nuclear magnetic resonance) and scattering (small angle neutron/X-ray scattering) techniques reveals that (i) below the micellization temperature of P84, PW12O403- exclusively binds to the propylene oxide moiety of P84 unimers and (ii) above the micellization temperature, PW12O403- mostly adsorbs on the ethylene oxide micellar corona. The preferential binding of the PW12O403- to the PPO chain over the PEO chains suggests that the binding is driven by the chaotropic effect and reinforced by the hydrophobic effect. At higher temperatures, the copolymer micellization leads to the displacement of PW12O403- from the PPO chain to the PEO chains. This study deepens the understanding of the subtle interplay between the chaotropic and hydrophobic effects in complex salt-organic matter solutions.