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Ultrasmall silver clusters in reduced state are difficult to synthesize since silver atoms tend to rapidly aggregate into bigger entities. Here, we show that dimers of reduced silver (Ag) are formed within the framework of a metal–organic framework provided with thioether arms in their walls (methioMOF), after reduction with NaBH of the corresponding Ag-methioMOF precursor. The resulting Ag-methioMOF catalyzes the methanation reaction of carbon dioxide (CO to CH hydrogenation reaction) under mild reaction conditions (1 atm CO, 4 atm H, 140 °C), with production rates much higher than Ag on alumina and even comparable to the state-of-the-art Ru on alumina catalyst (Ru–AlO) under these reaction conditions, according to literature results.

Host-guest chemistry within the confined space of metal-organic frameworks (MOFs) offers an almost unlimited myriad of possibilities, hardly accessible with other materials. Here we report the synthesis and physical characterization, with atomic resolution by single-crystal X-ray diffraction, of a novel water-stable tridimensional MOF, derived from the amino acid S-methyl-l-cysteine, {SrZn[(S,S)-Mecysmox](OH)(HO)}·9HO (1), and its application as a robust and efficient solid catalyst for the cycloaddition reaction of ethylene/propylene oxide with CO to afford ethylene/propylene carbonate with yields of up to 95% and selectivity of up to 100%. These results nicely illustrate the great potential of MOFs to be game changers for the selective synthesis of industrially relevant products, representing a powerful alternative to the current heterogeneous catalysts.

Understanding the host-guest chemistry in MOFs represents a research field with outstanding potential to develop in a rational manner novel porous materials with improved performances in fields such as heterogeneous catalysis. Herein, we report a family of three isoreticular MOFs derived from amino acids and study the influence of the number and nature of functional groups decorating the channels as a catalyst in hemiketalization reactions. In particular, a multivariate (MTV) MOF 3, prepared by using equal percentages of amino acids L-serine and L-mecysteine, in comparison to single-component (“traditional”) MOFs, derived from either L-serine or L-mecysteine (MOFs 1 and 2), exhibits the most efficient catalytic conversions for the hemiketalization of different aldehydes and ketalization of cyclohexanone. On the basis of the experimental data reported, the good catalytic performance of MTV-MOF 3 is attributed to the intrinsic heterogeneity of MTV-MOFs. These results highlight the potential of MTV-MOFs as strong candidates to mimic natural nonacidic enzymes, such as glycosidases, and to unveil novel catalytic mechanisms not so easily accessible with other microporous materials.

Allylic alcohol epoxidation and dehydrogenation reactivity is distinguished when VO(acac)2 is used in solution or anchored in a metal–organic framework (MOF). The chemical mechanism depends on the electronic profile of alkene substituents when the vanadyl complex is used in the homogenous phase. However, confinement effects imparted by MOF channels allow gaining control of the chemoselectivity toward the dehydrogenation product.

The preparation of novel efficient catalysts-that could be applicable in industrially important chemical processes-has attracted great interest. Small subnanometer metal clusters can exhibit outstanding catalytic capabilities, and thus, research efforts have been devoted, recently, to synthesize novel catalysts bearing such active sites. Here, we report the gram-scale preparation of Ag2subnanometer clusters within the channels of a highly crystalline three-dimensional anionic metal-organic framework, with the formula [Ag2]@AgNa{Ni[Cu(Mempba)]}·48HO [Mempba= N,N′-2,4,6-trimethyl-1,3-phenylenebis(oxamate)]. The resulting crystalline solid catalyst-fully characterized with the help of single-crystal X-ray diffraction-exhibits high catalytic activity for the catalytic Buchner ring expansion reaction.

Porous organic molecular materials represent an emergent field of research in Chemistry and Materials Science due to their unique combination of properties. To enhance their performance and expand the number of applications, the incorporation of hierarchical porosity is required, as exclusive microporosity entails several limitations. However, the integration of macropores in porous organic molecular materials is still an outstanding challenge. Herein, we report the first example of a hydrogen-bonded organic framework (MM-TPY) with hierarchical skeletal morphology, containing stable micro- and macroporosity. The crystal size, from micro to centimetre scale, can be controlled in a single step without using additives or templates. The mechanism of assembly during the crystal formation is compatible with a skeletal crystal growth. As proof of concept, we employed the hierarchical porosity as a platform for the dual, sequential and selective co-recognition of molecular species and microparticles.

Amides and esters are prevalent chemicals in Nature, industry and academic laboratories. Thus, it is not surprising that a plethora of synthetic methods for these compounds has been developed along the years. However, these methods are not 100% atom economical and generally require harsh reagents or reaction conditions. Here we show a “spring–loaded”, 100% atom–efficient amidation and esterification protocol which consists in the ring opening of cyclopropenones with amines or alcohols. Some alkyl amines react spontaneously at room temperature in a variety of solvents and reaction conditions, including water at different pHs, while other alkyl amines, aromatic amines and alcohols react in the presence of catalytic amounts of simple Cu salts or solids. A modular reactivity pattern (alkyl amines >> alkyl alcohols >> phenols >> aromatic amines) enables to design orthogonal and one–pot reactions on well–defined catalytic Multimetal–Organic Frameworks (M–MOFs, M= Cu, Ni, Pd), to easily functionalize the resulting cinnamides and cinnamic esters to more complex molecules. The strong resemblance of the amidation and esterification reaction conditions here reported with the copper–catalyzed azide–alkyne cycloaddition (CuAAC) allows to define this fast, clean and flexible protocol as a click reaction.

The synthesis of mixed-component metal-organic frameworks (MOFs) –including multivariate MOFs (MTV-MOFs), multicomponent MOFs, mixed-metals MOFs and mixed-ligands and metals MOFs– is becoming a very active research field. This is mainly based on the unique possibilities these materials offer to incorporate multiple functionalities and in how this heterogenity and complexity is translated in unexpected properties, which are not just the sum of each component. This review critically encompasses the progress made in this field, covering the synthetic approaches, and specially focusing on the current reported applications –such as gas storage and separation, catalysis, luminescence, conductivity, biological ones and water remediation. It also raises, as a perspective, some of the challenges the field has to overcome to reach their full-potential, and through two applications –(bio)enzymatic catalysis and synthesis of heterometallic subnanometric clusters and nanoparticles–, as exemplary cases, present some promising ways to take advantage of the intrinsic properties of mixed-components MOFs to make a breakthrough on the respective fields of application.