Enzyme-Powered Porous Micromotors Built from a Hierarchical Micro- and Mesoporous UiO-Type Metal-Organic Framework Yunhui Yang, # Xavier Arque ́ , # Tania Patiñ o,* Vincent Guillerm, Pascal-Raphael Blersch, Javier Pe ́ rez-Carvajal, Inhar Imaz,* Daniel Maspoch,* and Samuel Sa ́ nchez* Cite This: J. Am. Chem. Soc. 2020, 142, 20962-20967 Read Online ACCESS Metrics & More Article Recommendations * sı Supporting Information ABSTRACT: Here, we report the design, synthesis, and functional testing of enzyme-powered porous micromotors built from a metal-organic framework (MOF). We began by subjecting a presynthesized microporous UiO-type MOF to ozonolysis, to confer it with mesopores sufficiently large to adsorb and host the enzyme catalase (size: 6-10 nm). We then encapsulated catalase inside the mesopores, observing that they are hosted in those mesopores located at the subsurface of the MOF crystals. In the presence of H 2 O 2 fuel, MOF motors (or MOFtors) exhibit jet-like propulsion enabled by enzymatic generation of oxygen bubbles. Moreover, thanks to their hierarchical pore system, the MOFtors retain sufficient free space for adsorption of additional targeted species, which we validated by testing a MOFtor for removal of rhodamine B during self-propulsion. T he field of bioinspired micro- and nanomotors has evolved extensively so many synthetic structures have been reported over the past decade. 1 From the various ways these tiny motors can be powered, self-propulsion via chemical reactions is one of the most widely used being natural catalysts, such as enzymes, a promising alternative to achieve efficient and biocompatible systems. Several milestones toward real- world applications of such motors have been achieved, primarily in the fields of biomedicine 2-7 and environmental applications. 8-11 In those applications, porosity of the motor chassis is crucial, as it enables adsorption, transport, and/or release of cargo (e.g., drugs or pollutants), 8,12,13 its perform- ance being dictated mainly by its sorption capacity and its cargo transport versatility. 14-17 Among the alternatives available for developing enzyme- powered porous motors, metal-organic frameworks (MOFs) are an attractive choice. 18,19 MOFs exhibit very high surface areas, tunable pore sizes and shapes, and adjustable pore- surface functionality, suggesting their potential for myriad applications, including gas storage, separation, catalysis, contaminant removal, and drug delivery. 20, 21 In fact, researchers have used MOFs to build a stable and adaptable chassis for micro- and nanomotors, 18,22 in which motion is based on Marangoni effects, 23-26 magnetically driven cork- screw locomotion, 27,28 or bubble propulsion. 29-35 In parallel, researchers have demonstrated that biomolecules, particularly enzymes, can be encapsulated within MOFs for protection and to confer the MOFs with new functionalities, mainly in catalysis. For instance, Falcaro, Doonan, and co-workers explored biomimetic mineralization and controlled co-precip- itation to encapsulate several enzymes in ZIF-8. 36 Another challenging approach has required custom-made linkers to assemble MOFs with pores large enough (mesopores) to adsorb and host enzymes. For instance, the groups of Farha, 37 Zhou, 38 and Ma 39 exploited MOF mesopores to encapsulate various enzymes. Importantly, for a MOF to be used as the chassis of an enzyme-powered porous motor, it must combine mesopores sufficiently large to host the enzyme used for propulsion, with micropores of an appropriate size to adsorb and release additional guest species. Herein we report the design of an enzyme-powered, porous, MOF-based micromotor via compartmentalized encapsulation of the enzyme catalase within a hierarchical micro- and mesoporous MOF (Figure 1a). We chose catalase as a model enzyme, as it has been extensively used to induce ballistic propulsion through bubble propulsion via decomposition of H 2 O 2 . 40-43 Moreover, we selected a UiO-type Zr-MOF as the chassis because of its well-known water stability, 44 a condition that should fulfill any MOF intended to be used for the fabrication of motors powered by enzymatic reactions. In this design, another essential condition was the use of a UiO-type MOF with mesopores sufficiently large to host catalase (size: 6-10 nm) and micropores that preserve the ability to adsorb and/or release additional guest species. In order to rationally design this MOF, we decided to use an approach that we had developed earlier, whereby we subject presynthesized micro- porous MOFs functionalized with a mixture of linkers that do or do not contain olefins to ozonolysis, which selectively oxidizes the olefins to generate new mesopores. 45,46 To do so, we subjected a presynthesized UiO-type MOF to this ozonolysis process and then exploited the newly formed mesopores to host the catalase molecules. We began with the synthesis of a UiO-type Zr-fcu-MOF (hereafter called Zr-fcu-azo/sti-30%), formed by mixing 4,4′- Received: October 20, 2020 Published: December 4, 2020 Communication pubs.acs.org/JACS © 2020 American Chemical Society 20962 https://dx.doi.org/10.1021/jacs.0c11061 J. Am. Chem. Soc. 2020, 142, 20962-20967 Downloaded via UNIV DE BARCELONA on June 22, 2021 at 15:09:36 (UTC). See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles.