Stimulus-Responsive Modulation of Solvation Environments in Solid Catalysts

TL;DR

This paper explores how smart polymer coatings on solid catalysts can change the solvation environment, leading to better control over chemical reactions and improved catalyst performance.

Contribution

The paper introduces a new approach using stimulus-responsive polymers to modulate solvation environments in solid catalysts for enhanced catalytic behavior.

Findings

Polymer coatings can alter the solvation environment around catalytic sites, affecting reaction energy landscapes and selectivity.

Stimulus-responsive polymers enable the creation of smart catalysts with tunable activity and stability.

These materials can mimic biological self-regulation, offering potential for advanced chemical processes and nanoreactors.

Abstract

Liquid environments play a crucial
role in the biological processes
occurring in living organisms as well as in many human-made processes
involving electrochemistry, photo-, and thermocatalysis. In the majority
of these systems, aqueous phases are ubiquitous due to water’s
natural abundance. Water molecules, however, can exert large changes
in the chemical environment of catalytically active sites, altering
the reaction rates, selectivity, and catalyst stability. These solvation
effects induced by water molecules near catalytic sites can drastically
change the energy landscape and unlock unique reaction pathways with
far more favorable kinetics. In nature, living organisms couple these
complex interactions with detection, communication, and actuation
mechanisms to induce self-regulatory behavior, ensuring stability
of the system and thus long-term durability. Extrapolating this behavior
to heterogeneous catalysis is desirable because the resulting “smart
materials” can potentially unlock new chemical conversion processes
with higher atom efficiency, rates, and stability.

The combination
of polymer chemistry and heterogeneous catalysis
has introduced versatile approaches for creating materials that can
respond to cues in the reaction medium that alter the accessibility,
intrinsic activity, and selectivity of the catalyst. To achieve this,
one could combine stimulus-responsive polymers, which undergo a large
volumetric phase transition in response to an external stimulus, with
a solid catalyst. This chemo-mechanical response has been employed
to create a variety of nanoreactor vessels with stimulus-responsive
character that turn on- and off- depending on the reaction conditions.
In this Account, we focus on the impact of these polymer coatings
on the solvation environment around the active site and the implications
of these effects on the reaction energy landscape, molecular arrangement
of the solvent, electric fields at the catalyst–liquid interface,
binding energy, and mobility of surface reaction intermediates. These
seemingly subtle changes in solvent molecules induced by the presence
of polymers can have a tremendous impact on the development of bioinspired
heterogeneous catalysts, reliable chemical clocks, micro/nanoreactors,
and robots. The large library of polymer chemistries offers a plethora
of combinations of stimulus-responsive mechanisms (e.g., temperature,
pH, light, magnetic field, solvent composition), providing the possibility
of creating homeostatic catalysts à la carte.

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