Chemical Reactions in Frozen Aqueous Systems

Chemical transformations can proceed within partially frozen aqueous media owing to the unique microenvironments formed by ice and residual unfrozen solution. As ice crystals nucleate and grow, solutes are expelled into interstitial liquid films and grain‐boundary layers, producing highly concentrated pockets that promote reaction pathways normally inaccessible at low temperature. This freeze concentration effect accelerates acid–base, redox and organic reactions, while interactions at ice surfaces and interfaces can guide crystallisation, catalysis and molecular self‐assembly. Advanced imaging and spectroscopic techniques have revealed transient phase behaviour, glass transitions of solute‐rich regions and the role of pressure under isochoric conditions. Engineered dopants and charged interfaces further extend control over nucleation and reaction kinetics, enabling applications from enantioselective synthesis to environmental chemistry. Understanding these cryochemical processes is essential for innovations in pharmaceuticals storage, food preservation, polar biogeochemistry and the design of ice‐templated materials.

Research from Nature Portfolio

In situ visualisation of freezing and warming cycles has exposed a two‐stage process in aqueous solutions: a rapid formation of an interconnected ice framework interwoven with highly concentrated solute zones, followed by a slower freezing or glass transition of more dilute regions that resume crystallisation upon warming. Recent studies of isochoric freezing under constant‐volume constraints have, for the first time, captured nucleation events, crystal morphology and dynamic interface phenomena at elevated pressures, offering new insights into ice‐liquid interactions. Concurrently, controlled incorporation of dopants into ice has yielded self‐assembled fluidic grooves whose dimensions can be tuned to separate and transport nano- and micro-scale particles, demonstrating ice as a versatile template for microchannel fabrication.

Chemical Reactions in Frozen Aqueous Systems publication trend

The graph below shows the total number of articles in chemical reactions in frozen aqueous systems across all publications each year (not limited to Nature Index journals).

Technical terms

Freeze concentration effect: Enrichment of solutes in the residual liquid as ice forms, increasing local reagent concentrations and reaction rates.

Isochoric freezing: Phase transition at constant volume, generating high pressures that influence nucleation, crystal growth and phase equilibria.

Electrofreezing: Promotion of ice nucleation by electric fields or charged surfaces that align water molecules into ice-like configurations.

Freeze-concentrated solution (FCS): Liquid domains trapped between ice crystals with elevated solute concentration and distinct thermal behaviour.

Grain boundary region: Narrow, liquid-like layers between ice crystals where solutes accumulate and molecular mobility is enhanced.

References

1. Visualization of Freezing Process in situ upon Cooling and Warming of Aqueous Solutions. Scientific Reports (2014).
2. Revealing isochoric water nucleation: a visual study. Scientific Reports (2024).
3. Fluidic Grooves on Doped-Ice Surface as Size-Tunable Channels. Scientific Reports (2015).
4. Electro-Freezing of Supercooled Water Is Induced by Hydrated Al3+ and Mg2+ Ions: Experimental and Theoretical Studies. Journal of the American Chemical Society (2023).
5. Advances in Cryochemistry: Mechanisms, Reactions and Applications. Molecules (2021).
6. Accelerated dissolution of iron oxides in ice. Atmospheric Chemistry and Physics (2012).