Supramolecular Gels as Active Tools for Reaction Engineering

Supramolecular gels, assembled from low-molecular-weight gelators (LMWGs), are fascinating soft materials for use in synthesis, combining aspects of hetero- and homogeneous systems. The unique combination of environments within a gel offers the ability to control reactivity in new ways. For example, self-assembly into a gel network can modify the reactivity of catalytic sites on the LMWG. Controlling the assembly of multiple LMWGs can result in integrated gels with orthogonal activities that could not normally coexist. Enzymes encapsulated within self-assembled gels can exhibit superactivity, extending their use into solvent media more appropriate for organic synthesis. Highly reactive species, such as ligand-free nanoparticles or moisture/air-sensitive organometallics, can be protected within the unique environment of a supramolecular gel, facilitating their use in ambient conditions, potentially opening up the use of such species to nonspecialist researchers. Beyond fundamental chemistry, performing reactions in gels leads to the emerging concept of gels as "nanoreactors". Smart chemical engineering methods are enabling the fabrication of materials and devices for use in a variety of synthetic workflows, potentially transforming the way synthesis is done. In summary, this review provides an overview of key concepts and signposts the way toward future developments of gels as active tools for reaction engineering.