Smart catalysts offer the control of chemical processes and sequences of transformations, and catalysts with unique catalytic behavior can afford chiral products or promote successive polymerization. To meet advanced demands, the key to constructing smart catalysts is to incorporate traditional catalytic functional groups with trigger-induced factors. Molecular machines with dynamic properties and particular topological structures have typical stimulus-responsive features. In recent years, scientists have made efforts to utilize molecular machines (molecular switches, rotaxanes, motors, etc.) as scaffolds to develop smart catalysts. This Minireview focuses on the achievements of developing catalysts encapsulated in molecular machines and their remarkable specialties. This strategy is believed to provide more potential applications in switchable reactions, asymmetric synthesis, and processive catalysis.

A new family of bipodal anion transporters based on chalcogen-containing scaffolds has been designed and synthesized. Though structurally related to the well-studied tripodal anionophores, these molecules are simpler with only two anion-binding sites. However, the activities remain high. Anion transport could be facilitated by the new transporter at an exceptionally low loading of transporter/lipid ratio of 1:500000. This impressive efficiency is comparable with the most active one from the tren-based tripodal series. To investigate influences from different scaffolds and substituent groups, lipophilicity, anion-binding property, and transport activity of each molecule were studied. It was found that the bridge atom has a major impact on transport activities mainly as a result of anion-binding differences. The results also suggest that chalcogen can act as a key structural modulator to develop highly effective anion transporters and optimize their activities.

Glutathione peroxidase (GPx) is a vital antioxidant enzyme involved in the reduction of reactive oxygen species and protects cells from oxidative damage. Consequently enormous efforts have been devoted to developing artificial catalysts with GPx function. Besides the research on enhancing the catalytic activity of GPx mimics, the design and construction of smart GPx models has also inspired great interest. Herein, a novel photo-responsive selenium-containing vesicular GPx model was successfully constructed by supramolecular self-assembly of the cationic surfactant PyC₁₀AzoC₁₀Py with benzeneseleninic acid (PhSeO₂H) through hydrophobic and electrostatic interactions in aqueous media. This selenium-containing vesicular catalyst showed remarkable GPx-like activity, which is 692 times more effective than PhSeO₂H for the reduction of cumene hydroperoxide (CUOOH) by 4-nitrobenzenethiol (NBT). Interestingly, when an equimolar amount of α-CD was added, the GPx-like activity of the catalytic vesicle declines remarkably due to the vesicle disaggregation in the presence of α-CD. Whereas the biomimetic system was irradiated by UV light at 365 nm, the catalytic vesicle was formed again and the GPx-like activity recovered.

A Ca²⁺-responsive artificial selenoenzyme was constructed by computational design and engineering of recoverin with the active center of glutathione peroxidase (GPx). By combining the recognition capacity for the glutathione (GSH) substrate and the steric orientation of the catalytic selenium moiety, the engineered selenium-containing recoverin exhibits high GPx activity for the catalyzed reduction of H₂O₂ by glutathione (GSH). Moreover, the engineered selenoenzyme can be switched on/off by Ca²⁺-induced allosterism of the protein recoverin. This artificial selenoenzyme also displays excellent antioxidant ability when it was evaluated using a mitochondrial oxidative damage model, showing great potential for controlled catalysis in biomedical applications.

Enzyme-mediated self-healing of dynamic covalent bond-driven protein hydrogels was realized by the synergy of two enzymes, glucose oxidase (GOX) and catalase (CAT). The reversible covalent attachment of glutaraldehyde to lysine residues of GOX, CAT, and bovine serum albumin (BSA) led to the formation and functionalization of the self-healing protein hydrogel system. The enzyme-mediated protein hydrogels exhibit excellent self-healing properties with 100 % recovery. The self-healing process was reversible and effective with an external glucose stimulus at room temperature.

Enzyme-mediated self-healing of dynamic covalent bond-driven protein hydrogels was realized by the synergy of two enzymes, glucose oxidase (GOX) and catalase (CAT). The reversible covalent attachment of glutaraldehyde to lysine residues of GOX, CAT, and bovine serum albumin (BSA) led to the formation and functionalization of the self-healing protein hydrogel system. The enzyme-mediated protein hydrogels exhibit excellent self-healing properties with 100 % recovery. The self-healing process was reversible and effective with an external glucose stimulus at room temperature.

Cucurbituril (CB), a well-known macrocyclic cavitand, has been used extensively to construct supramolecular aggregates. Based on host-guest intertactions, an adamantanyl derivative guest molecule was designed and synthesized to prepare a supramolecular amphiphile with cucurbit[7]uril. In aqueous solution, the cucurbit[7]uril based supramolecular amphiphiles self-assemble into well-defined vesicles, and their disassembly can be achieved by addition of excess competitive agent 1-adamantanamine hydrochloride. This vesicle functions as a new nanocapsule to encapsulate molecules within its hollow cavity. Through competitive disassembly of supramolecular amphiphiles, the vesicles behave as a novel drug delivery carrier.

For developing an efficient nanoenzyme system with self-assembly strategy, gold nanocrystal micelles (Au NC micelles) with inserted catalytic Zn(II) centers were constructed by self-assembly of a catalytic ligand [N,N-bis(2-aminoethyl)-N′-dodecylethylenediamine] Zn(II) complexes (Zn(II)L) on the surface of Au NC via hydrophobic interaction. The functionalized Au NC micelles acted as an excellent nanoenzyme model for imitating ribonuclease. The catalytic capability of the Au NC micelles was evaluated by accelerating the cleavage of 2-hydroxypropyl p-nitrophenyl phosphate (HPNP). These functionalized Au NC micelles exhibited considerable ribonuclease-like activities by a factor of 4.9×10⁴ (k_cat/k_uncat) for the cleavage of HPNP in comparison to the spontaneous cleavage of HPNP at 37°C. The catalytic capability of the functionalized Au NC micelles can be considerably compared to other models reported previously as nanoenzymes under the comparable conditions.