Controlling the shape of metal-organic framework (MOF) crystals is important for understanding their crystallization and useful for myriad applications. However, despite the many advances in shaping of inorganic nanoparticles, post-synthetic shape control of MOFs and, in general, molecular crystals remains embryonic. Herein we report using a simple wet-chemistry process at room temperature to control the anisotropic etching of colloidal ZIF-8 and ZIF-67 crystals. Our work enables uniform reshaping of these porous materials into unprecedented morphologies, including cubic and tetrahedral crystals, and even hollow boxes, via acid-base reaction and subsequent sequestration of leached metal ions. Etching tests on these ZIFs reveal that etching occurs preferentially in the crystallographic directions richer in metal-ligand bonds; that, among these directions, the etching rate tends to be faster on the crystal surfaces of higher dimensionality; and that the etching can be modulated by adjusting the pH of the etchant solution. KeywordsMetal-Organic Frameworks; Zeolitic-Imidazolate Frameworks; anisotropic etching; hollow particles; porosity Chemical etching is an ancient fabrication method that was used by metal and glass craftsmen to obtain sophisticated surface designs. With the advent of controlling the etching orientation at the microscale and nanoscale, anisotropic wet-chemical etching has become highly useful for shaping many materials for diverse applications.[1,2] For example, the anisotropic wet-chemical etching of single-crystal silicon in the presence of a base is essential in microelectronics manufacturing.[1] Anisotropic etching can also be applied to preparation of metal nanocrystals from oxidative species and coordination ligands, for which it enables unprecedented morphologies and complexities, and unique physical properties.[2] Here, we introduce the concept of anisotropic wet-chemical etching for metal-organic frameworks (MOFs)-specifically, for the zeolitic-imidazolate framework (ZIF) subfamily. Figure S1).[9] Recently, several studies have shown that the crystal growth of ZIF-8 starts with formation of cubes exposing six {100} facets, which gradually evolve into truncated rhombic dodecahedra exposing six {100} and twelve {110} facets, and finally, into the thermodynamically more stable rhombic dodecahedra, in which only the twelve {110} facets are exposed ( Figure 1a). [10,11] Figure 1a illustrates the different exposed crystallographic planes for the cubes and for the truncated and non-truncated rhombic dodecahedra. As shown in this figure, each crystal shape has different exposed crystallographic planes, and each crystallographic plane, a distinct chemical composition. In ZIF-8, {100} and {211} planes contain several Zn-2-MIM linkages, whereas the {110} and {111} planes do not contain any of these linkages ( Figure 1b).By exploiting the aforementioned differences, we devised a method for anisotropic wet etching of colloidal crystals of isostructural ZIF-8 and ZIF-67. Our approach combines ...

Bacteriophages are promising therapeutic agents that can be applied to different stages of the commercial food chain. In this sense, bacteriophages can be orally administered to farm animals to protect them against intestinal pathogens. However, the low pH of the stomach, the activities of bile and intestinal tract enzymes limit the efficacy of the phages. This study demonstrates the utility of an alginate/CaCO3 encapsulation method suitable for bacteriophages with different morphologies and to yield encapsulation efficacies of ~100%. For the first time, a cocktail of three alginate/CaCO3-encapsulated bacteriophages was administered as oral therapy to commercial broilers infected with Salmonella under farm-like conditions. Encapsulation protects the bacteriophages against their destruction by the gastric juice. Phage release from capsules incubated in simulated intestinal fluid was also demonstrated, whereas encapsulation ensured sufficient intestinal retention of the phages. Moreover, the small size of the capsules (125–150 μm) enables their use in oral therapy and other applications in phage therapy. This study evidenced that a cocktail of the three alginate/CaCO3-encapsulated bacteriophages had a greater and more durable efficacy than a cocktail of the corresponding non-encapsulated phages in as therapy in broilers against Salmonella, one of the most common foodborne pathogen.

Controlling the shape of metal-organic framework (MOF) crystals is important for understanding their crystallization and useful for myriad applications.H owever,d espite the many advances in shaping of inorganic nanoparticles,postsynthetic shape control of MOFs and, in general, molecular crystals remains embryonic.H erein, we report using as imple wet-chemistry process at room temperature to control the anisotropic etching of colloidal ZIF-8 and ZIF-67 crystals.Our work enables uniform reshaping of these porous materials into unprecedented morphologies,i ncluding cubic and tetrahedral crystals,and even hollow boxes,b yanacid-base reaction and subsequent sequestration of leached metal ions.E tching tests on these ZIFs reveal that etching occurs preferentially in the crystallographic directions richer in metal-ligand bonds;t hat, along these directions,the etching rate tends to be faster on the crystal surfaces of higher dimensionality;a nd that the etching can be modulated by adjusting the pH of the etchant solution.Chemical etching is an ancient fabrication method that was used by metal and glass craftsmen to obtain sophisticated surface designs.W ith the advent of controlling the etching orientation at the microscale and nanoscale,anisotropic wetchemical etching has become highly useful for shaping many materials for diverse applications. [1,2] Fore xample,t he anisotropic wet-chemical etching of single-crystal silicon in the presence of ab ase is essential in microelectronics manufacturing. [1] Anisotropic etching can also be applied to preparation of metal nanocrystals from oxidative species and coordination ligands,f or which it enables unprecedented morphologies and complexities,a nd unique physical properties. [2] Herein, we introduce the concept of anisotropic wetchemical etching for metal-organic frameworks (MOFs) and, in particular,f or the zeolitic-imidazolate framework (ZIF) subfamily.MOFs (and by extension, ZIFs) are an emerging class of porous materials that show extremely large surface areas (S BET )a nd potential for myriad applications,i ncluding gas sorption and separation, catalysis,s ensing,a nd biomedicine, among others. [3,4] MOFs are built up from metal ions/clusters connected through organic linkers.T heir exposed crystal facets,e dges,a nd vertices can exhibit different chemical compositions.W ehypothesized that agents capable of breaking the coordination bonds between the metal ions/clusters and the organic linkers could be exploited to preferentially etch specific external crystal surfaces (with more density of coordination bonds) over others.W ee nvisioned that such control would enable us to post-synthetically tailor the shape of MOF crystals.T od ate,p ost-synthetic random etching of MOF crystals using H + ,N a + ,a nd quinone has already been demonstrated. [5,6] Inspired by similar results with zeolites,this strategy has enabled researchers to prepare hierarchical MOF crystals and/or create macropores on the MOF crystal surfaces. [7,8] However, to date,n oo ne has demonstrated the ab...

Herein we report a water-induced single-crystal to single-crystal transformation that involves the formation of hetero-bimetallic paddlewheel clusters in coordination polymers. Through this transformation, which involves the cleavage and formation of different coordination bonds, two different Cu(ii)-Zn(ii) and Cu(ii)-Ni(ii) paddlewheel units exhibiting a 1 : 1 metal ratio were created.