Jorge Albalad

La química reticular, representada principalmente por los MOFs y COFs, ha transformado la química de materiales al permitir el diseño de redes cristalinas con precisión atómica y molecular. Su naturaleza modular, junto con el control sintético y post-sintético de sus estructuras, convierte a estos materiales en plataformas altamente versátiles para ajustar de forma dirigida sus propiedades físicas y químicas. Este artículo de opinión presenta al lector una visión general de cómo estos avances han impulsado el paso desde materiales cuya estructura se observa hacia materiales cuya función puede diseñarse desde su síntesis.

Covalent organic frameworks (COFs) are promising materials for wide-ranging applications. Challenges with coating them onto surfaces have however limited their wider implementation in practice. We report an acoustomicrofluidic nebulization platform that enables rapid, one-step synthesis of highly crystalline COFs and their direct deposition as a coating under ambient conditions. Demonstrated with both two- and three-dimensional imine-based COFs, the method yields uniform COF films with nanometer to micrometer thicknesses, tuned simply by adjusting the nebulization time. Unlike conventional COF coating approaches, this strategy eliminates the need for any postsynthetic substrate heating or processing, thereby offering a general and scalable route for fabricating functional COF coatings on a variety of sensitive and complex substrates, including living tissue. As proof of concept, we demonstrate that COFs can constitute protective coatings on plant leaves for solar ultraviolet shielding, thus highlighting the potential of the platform to extend the deployment of COFs in real-world devices, biological systems, and environmental interfaces.

Molecules are typically synthesized through stepwise processes involving chemical reactions between simple molecular precursors. Here, we report an advance in the synthesis of new organic molecules based on the approach of clip-off chemistry, in which molecules are excised from ordered, extended organic structures. We synthesized macrocycles by selectively cleaving them out of covalent organic frameworks. The synthesized macrocycles include eight macrocyclic polyamides with 114-, 138-, and 162-atom rings, and one 114-atom ring macrocyclic polyimide. This excision approach expands the scope of chemical organic synthesis to previously inaccessible macromolecules.

Confining chemical reactions within microdroplets has attracted significant attention from chemists due to the accelerated reaction rates resulting from the drastically smaller reaction volumes than in standard solutions. Herein we report that, beyond its widespread use for producing dry-powder formulations for industries (e.g. pharmaceuticals and food) via the atomization of microdroplets followed by drying in a hot gas stream, spray-drying can also be employed in organic synthesis. Specifically, we used spray-drying to run three model reactions: a Schiff-base condensation, a Claisen-Schmidt reaction, and acylation of amines, for synthesizing small organic molecules. Our results showcase that, compared to traditional methods, spray-drying can reduce reaction times without compromising (high) yields, paving the way for its use as a scalable method for industrial-scale organic synthesis.

Control of selectivity in organic synthesis is essential for guiding chemical reactions towards a desired product when multiple outcomes are possible. Since organic reactions can often yield a range of products, selectivity control ensures that the target product is favoured over others. Herein, we present a new synthetic approach, Clip-off Chemistry, which provides precise selectivity control in the synthesis of organic (macro)molecules through selective orthogonal cleavage within extended structures containing such (macro)molecules, which, in turn, spontaneously form when these extended structures are assembled. We have applied this concept to the synthesis of seven novel macrocycles by selectively cleaving double or triple bonds via ozonolysis within covalent-organic frameworks (COFs). With this demonstration, we believe that Clip-off Chemistry will soon provide generalized access to previously inaccessible (macro)molecules and polymers for diverse applications.

Herein, we present a novel methodology for synthesizing metal clusters or secondary building units (SBUs) that are subsequently employed to construct innovative metal-organic frameworks (MOFs) via dynamic covalent chemistry. Our approach entails extraction of SBUs from preformed MOFs through complete disassembly by clip-off chemistry. The initial MOF precursor is designed to incorporate the desired SBU, connected exclusively by cleavable linkers (in this study, with olefinic bonds). Cleavage of all the organic linkers (in this study, via ozonolysis under reductive conditions) liberates the SBUs functionalized with aldehyde groups. Once synthesized, these SBUs can be further reacted with amines in dynamic covalent chemistry to build new, rationally designed MOFs.

Herein we address the question of whether a supramolecular finite metal-organic structure such as a cage or metal-organic polyhedron (MOP) can be synthesized via controlled cleavage of a three-dimensional (3D) metal-organic structure. To demonstrate this, we report the synthesis of a Cu(II)-based cuboctahedral MOP through orthogonal olefinic bond cleavage of the cavities of a 3D, Cu(II)-based, metal-organic framework (MOF). Additionally, we demonstrate that controlling the ozonolysis conditions used for the cleavage enables Clip-off Chemistry synthesis of two cuboctahedral MOPs that differ by their external functionalization: one in which all 24 external groups represent a mixture of aldehydes, carboxylic acids, acetals and esters, and one in which all are aldehydes.

MOFs formed from 8-connecting nodes and 4-connecting linkers can have the flu , scu and csq topologies. Here we show design criteria for making the rare sqc topology and how topology can be used to generate distinct post-synthetic metalation sites.

Nanoconfinement in metal-organic framework (MOF) pores can lead to the isolation of unusual or reactive metal complexes. However, MOFs that support the stabilization and precise structural elucidation of metal complexes and small metal clusters are rare. Here, we report a thermally and chemically stable zirconium-based MOF (University of Adelaide Material-1001, UAM-1001) with a high density of free bis-pyrazolyl units that can confine mono- and dinuclear metal complexes. The precursor MOF, UAM-1000, has a high degree of structural flexibility, but post synthetic modification with a bracing linker, biphenyl-4,4 '-dicarboxylic acid, partially rigidifies the MOF (UAM-1001). This allows "matrix isolation" and detailed structural elucidation of postsynthetically added dimeric complexes bound within a tetradentate binding site formed by two linkers. Dimeric species [Co2Cl4], [Cu2Cl4], [Ni2Cl3(H2O)(2)]Cl, and [Rh-2(CO)(3)Cl-2] were successfully isolated in UAM-1001 and characterized by single-crystal X-ray diffraction. Comparison of the UAM-1001 isolated species with similar complexes in the solid state reveals that UAM-1001 can significantly distort the structures and enforce notably shorter metal-metal distances. For example, MOF tethering allows isolation of a [Cu2Cl4] complex that rapidly reacts with water in the solid state. The stability, porosity, and modulated flexibility of UAM-1001 provide an ideal platform material for the isolation and study of new dimeric complexes and their reactivity.