Reticular frameworks are promising candidates for chiral environments, yet most rely on static stereogenic units, overlooking adaptive host-guest interactions in enantioselective recognition. We report a modular postsynthetic click strategy to install amino acid-derived peptidic moieties into UiO-68 frameworks without compromising crystallinity. Only the histidine-functionalized material exhibits high enantioselectivity for cetirizine. Simulations reveal adaptive interaction pockets, emphasizing the importance of local pore reorganization in chiral molecular recognition.

Photoredox catalysis has emerged as a powerful strategy for promoting redox reactions under mild conditions, but its translation from homogeneous to heterogeneous catalysts in porous solids remains limited. Metal-organic frameworks (MOFs) offer unique opportunities to bridge this gap by combining tailorable photoactive architectures with high stability, large surface areas, and modular control over reactivity via component selection. Despite recent progress, most photocatalytic MOF-based systems have focused on water splitting or CO2 reduction, whereas applications in organic synthesis remain virtually unexplored. Here, we report a titanium-iron MOF (MUV-1001) built from heterometallic TiFe2 metal-oxo clusters that operates as an intrinsically active visible-light photoredox catalyst. This platform enables single-electron transfer reactivity under irradiation, as demonstrated in a decarboxylative Giese reaction, and it represents an example of noble-metal- and additive-free C–C bond formation mediated by a pristine crystalline reticular material. Our findings highlight the potential of cluster-based design to access intrinsically photoactive systems, where subtle changes in composition dictate reactivity, even across isostructural families.

The structural and compositional diversification of Metal-Organic Frameworks (MOFs) continues to grow, along with the opportunities they offer in H-2 photoevolution or CO2 photoreduction. This often requires the use of metal co-catalysts for improving the efficiency and selectivity of the reaction. However, most studies often overlook how the integration of these two components can be used to tailor the photocatalytic performance of a given framework. Taking advantage of a new synthetic methodology that allows the growth of titanium-based MUV-10 crystals through continuous injection of its components, here it is demonstrated how the time-resolved injection of Pt nanoparticles (NPs) at different stages of crystal growth results in tunable MOF/Pt heterojunctions with varying photocatalytic efficiencies, which can be used to boost performance by up to 2.5 times depending on the injection time.

The soft nature of Metal-Organic Frameworks (MOFs) sets them apart from other non-synthetic porous materials. Their flexibility allows the framework components to rearrange in response to environmental changes, leading to different states and properties. The work extends this concept to titanium frameworks, demonstrating control over charge transport in porous molecular crystals. MUV-35 is a two-fold catenated framework composed of heterometallic TiMn2 trimers and electron donor 4,4',4″-(benzo[1,2-b:3,4-b':5,6-b″]trithiophene-2,5,8-triyl)tribenzoic acid (H3BTTTB) linkers, forming a rare sit-c net topology that can fold to reduce its volume by ≈40% through a single-crystal transformation controlled by linker conformation in open, intermediate, and closed states. This process, driven by a free energy difference of ≈300 kJ mol-1, originates from the formation of a continuous network of non-covalent interactions that force the spontaneous loss of the solvent in the pores of the framework to establish charge transport pathways that afford photocurrents of 2.5 × 10-3 S m-1 under visible light for an ON/OFF ratio (∆R) of four orders of magnitude. This photoconductivity rivals the best conductivity values described for though-transport conductive MOFs while maintaining a porosity of ≈1.000 m2 g-1.

Despite their potential to control charge separation and redox activity, deliberate strategies to distort metal-oxo clusters in molecular frameworks remain limited. Here we present a proof-of-concept for cluster strain engineering using the titanium-organic framework MUV-10 as a model. Replacing Ca2+ with larger alkaline-earth cations (Sr2+, Ba2+) induces predictable distortions of Ti2M2 clusters and a cubic-to-tetragonal cell transformation while preserving the overall connectivity. This local strain alters Ti-O coordination geometry, enhances ligand-to-metal charge transfer, and promotes the photogeneration of Ti3+ sites, as validated by photocatalytic CO2 methanation under standardized conditions. Importantly, the extent of distortion follows the trend anticipated from the Goldschmidt tolerance factor, a classical descriptor from perovskite chemistry, that we repurpose here to rationalize strain in reticular frameworks. Taken together, these findings establish a conceptual link between oxide catalysis and reticular chemistry, highlighting cluster strain as a potential structural switch to modulate redox reactivity in molecular solids.

Metal-Organic Frameworks can be grafted with amines by coordination to metal vacancies to create amine-appended solid adsorbents, which are being considered as an alternative to using aqueous amine solutions for CO 2 capture. In this study, we propose an alternative mechanism that does not rely on the use of neutral metal vacancies as binding sites but is enabled by the structural adaptability of heterobimetallic Ti 2 Ca 2 clusters. The combination of hard (Ti 4+ ) and soft (Ca 2+ ) metal centers in the inorganic nodes of the framework enables MUV-10 to adapt its pore windows to the presence of triethylenetetramine molecules. This dynamic cluster response facilitates the translocation and binding of tetraamine inside the microporous cavities to enable the formation of bis-coordinate adducts that are stable in water. The extension of this grafting concept from MUV-10 to larger cavities not restrictive to CO 2 diffusion will complement other strategies available for the design of molecular sorbents for decarbonization applications.

The extensive use of pesticides to ensure global food production presents significant threats to both human health and the environment. In this study, the photochemical, redox, and acid-base properties of Zr-metal-organic polyhedra (Zr-MOP) and polyoxometalates (POM) are utilized to fabricate functional hybrid salts, denoted as [Zr-MOP][POM], designed for pesticide detoxification. Upon light irradiation, [Zr-MOP][POM] salts generate a charge-separated state with oxidizing properties. This activated state selectively photooxidizes highly toxic and persistent fenamiphos into fenamiphos sulfoxide and subsequently hydrolytically breaks down it into non-toxic 3-methyl-4-(methylsulfinyl)phenol and phosphate components. The hydrolytic degradation of fenamiphos is facilitated by the reduced basicity of the 3-methyl-4-(methylsulfinyl)phenolate residue (Delta pKb = -2.4) in the photooxidized form of the pesticide molecule. Furthermore, the hybrid salts demonstrate efficacy in the breakdown of multicomponent pesticide mixtures such as fenamiphos and methylparaoxon. The photooxidative, hydrolytic, and redox properties of Zr-metal-organic polyhedra and polyoxometalate components in hybrid salts synergistically interplay for the efficient detoxification of multicomponent mixtures of persistent toxic organophosphate pesticides. image

The increasing use of Metal-Organic Frameworks (MOFs) in separation, catalysis, or storage is linked to the targeted modification of their composition or porosity metrics. While modification of pore shape and size necessarily implies the assembly of alternative nets, compositional changes often rely on postsynthetic modification adapted to the functionalization or exchange of the organic linker or the modification of the inorganic cluster by metal exchange methods. We describe an alternative methodology that enables the integration of both types of modification, structural and compositional, in titanium MOFs by metal exchange reaction of the heterometallic cluster Ti2Ca2. A systematic analysis of this reactivity with MUV-10 is used to understand which experimental variables are crucial to enable replacement of calcium only or to integrate metal exchange with structural transformation. The isoreticular expanded framework, MUV-30, is next used to template the formation of MUV-301, a titanium framework not accessible by direct synthesis that displays the largest mesoporous cages reported to date. Given that the interest of Ti MOFs in photoredox applications often meets the limitations imposed by the challenges of titanium solution chemistry to design concrete candidates, this soft strategy based on preassembled frameworks will help integrate specific combinations of metals into high porosity architectures.

The combination of compositional versatility and topological diversity for the integration of electroactive species into high-porosity molecular architectures is perhaps one of the main appeals of metal-organic frameworks (MOFs) in the field of electrocatalysis. This premise has attracted much interest in recent years, and the results generated have also revealed one of the main limitations of molecular materials in this context: low stability under electrocatalytic conditions. Using zirconium MOFs as a starting point, in this work, we use this stability as a variable to discriminate between the most suitable electrocatalytic reaction and specific topologies within this family. Our results revealed that the PCN-224 family is particularly suitable for the electroreduction of molecular nitrogen for the formation of ammonia with faradaic efficiencies above 30% in the presence of Ni2+ sites, an activity that improves most of the catalysts described. We also introduce the fluorination of porphyrin at the meso position as a good alternative to improve both the activity and stability of this material under electrocatalytic conditions.

Research on metal-organic frameworks is shifting from the principles that control the assembly, structure, and porosity of these reticular solids, already established, into more sophisticated concepts that embrace chemical complexity as a tool for encoding their function or accessing new properties by exploiting the combination of different components (organic and inorganic) into these networks. The possibility of combining multiple linkers into a given network for multivariate solids with tunable properties dictated by the nature and distribution of the organic connectors across the solid has been well demonstrated. However, the combination of different metals remains still comparatively underexplored due to the difficulties in controlling the nucleation of heterometallic metal-oxo clusters during the assembly of the framework or the post-synthetic incorporation of metals with distinct chemistry. This possibility is even more challenging for titanium-organic frameworks due to the additional difficulties intrinsic to controlling the chemistry of titanium in solution. In this perspective article we provide an overview of the synthesis and advanced characterization of mixed-metal frameworks and emphasize the particularities of those based in titanium with particular focus on the use of additional metals to modify their function by controlling their reactivity in the solid state, tailoring their electronic structure and photocatalytic activity, enabling synergistic catalysis, directing the grafting of small molecules or even unlocking the formation of mixed oxides with stoichiometries not accessible to conventional routes.

Changing the perception of defects as imperfections in crystalline frameworks into correlated domains amenable to chemical control and targeted design might offer opportunities for the design of porous materials with superior performance or distinctive behavior in catalysis, separation, storage, or guest recognition. From a chemical standpoint, the establishment of synthetic protocols adapted to control the generation and growth of correlated disorder is crucial to consider defect engineering a practicable route towards adjusting framework function. By using UiO-66 as experimental platform, we systematically explored the framework chemical space of the corresponding defective materials. Periodic disorder arising from controlled generation and growth of missing cluster vacancies can be chemically controlled by the relative concentration of linker and modulator, which has been used to isolate a crystallographically pure “disordered” reo phase. Cs-corrected scanning transmission electron microscopy is used to proof the coexistence of correlated domains of missing linker and cluster vacancies, whose relative sizes are fixed by the linker concentration. The relative distribution of correlated disorder in the porosity and catalytic activity of the material reveals that, contrarily to the common belief, surpassing a certain defect concentration threshold can have a detrimental effect.

Titanium-organic frameworks offer distinctive opportunities in the realm of metal-organic frameworks (MOFs) due to the integration of intrinsic photoactivity or redox versatility in porous architectures with ultrahigh stability. Unfortunately, the high polarizing power of Ti4+ cations makes them prone to hydrolysis, thus preventing the systematic design of these types of frameworks. We illustrate the use of heterobimetallic cluster Ti2Ca2 as a persistent building unit compatible with the isoreticular design of titanium frameworks. The MUV-12(X) and MUV-12(Y) series can be all synthesized as single crystals by using linkers of varying functionalization and size for the formation of the nets with tailorable porosity and degree of interpenetration. Following the generalization of this approach, we also gain rational control over interpenetration in these nets by designing linkers with varying degrees of steric hindrance to eliminate stacking interactions and access the highest gravimetric surface area reported for titanium(IV) MOFs (3000 m2 g-1).

Abstract The value of covalent post‐synthetic modification in expanding the chemistry and pore versatility of reticular solids is well documented. Here we use mesoporous crystals of the metal–organic framework (MOF) UiO‐68‐TZDC to demonstrate the value of tetrazine connectors for all‐purpose inverse electron‐demand Diels–Alder ligation chemistry. Our results suggest a positive effect of tetrazine reticulation over its reactivity for quantitative one‐step functionalization with a broad scope of alkene or alkyne dienophiles into pyridazine and dihydropyridazine frameworks. This permits generating multiple pore environments with diverse chemical functionalities and the expected accessible porosities, that is also extended to the synthesis of crystalline fulleretic materials by covalent conjugation of fullerene molecules.

The CuGHK peptide-based porous material acts as a heterogeneous organocatalyst in the Henry reaction due to a periodic distribution of pockets decorated with lysine side chain active sites.

A selective grafting route for heterometallic MOFs is described by Carlos Martí-Gastaldo and co-workers in their Research Article on page 11868. The different chemistry of Ti(IV) and Ca(II) sites is used to direct selective coordination of amines to the latter. This enables the combination of Lewis acid titanium centers and available -NH2 sites in two sizeable pores for cooperative cycloaddition of CO2 to epoxides at room temperature and atmospheric pressure.

We introduce the first example of isoreticular titanium–organic frameworks, MUV-10 and MUV-12, to show how the different affinity of hard Ti(IV) and soft Ca(II) metal sites can be used to direct selective grafting of amines. This enables the combination of Lewis acid titanium centers and available -NH 2 sites in two sizeable pores for cooperative cycloaddition of CO 2 to epoxides at room temperature and atmospheric pressure. The selective grafting of molecules to heterometallic clusters adds up to the pool of methodologies available for controlling the positioning and distribution of chemical functions in precise positions of the framework required for definitive control of pore chemistry.

We report a crystalline supramolecular framework assembled by H-bonding interactions between covalently fused monomers equipped with two guanine-cytosine nucleobase pairs.

Defect engineering is a valuable tool to tune the properties of metal-organic frameworks. However, defect chemistry remains still predominantly limited to UiO-type MOFs. We describe the preferential formation of missing cluster defects in heterometallic titanium-organic frameworks of the MUV-10 family when synthesised in sub-stoichiometric linker conditions. Our results show the value of integrating experimental work, computational modelling and thorough characterization in rationalizing the impact of defects over the porosity and structure of this family of materials. Correlation of experiment with computational models reveals the dominance of missing cluster vacancies in the pore size distribution of defective MUV-10. These same models were used to investigate the correlation of defects by synchrotron X-ray diffraction. The diffraction at low reflection angles is dominated by diffuse scattering that is indicative of short-range order and cannot be indexed to the defective structural models generated. In addition to the low atomic scattering factor of titanium, these results confirm the need for high-resolution electron microscopy methods for modelling nanoscale disorder in titanium MOFs.

The use of Metal-Organic Frameworks as crystalline matrices for the synthesis of multiple component or multivariate solids by the combination of different linkers into a single material has emerged as a versatile route to tailor the properties of single-component phases or even access new functions. This approach is particularly relevant for Zr6-MOFs due to the synthetic flexibility of this inorganic node. However, the majority of materials are isolated as polycrystalline solids, which are not ideal to decipher the spatial arrangement of parent and exchanged linkers for the formation of homogeneous structures or heterogeneous domains across the solid. Here we use high-throughput methodologies to optimize the synthesis of single crystals of UiO-68 and UiO-68-TZDC, a photoactive analogue based on a tetrazine dicarboxylic derivative. The analysis of the single linker phases reveals the necessity of combining both linkers to produce multivariate frameworks that combine efficient light sensitization, chemical stability, and porosity, all relevant to photocatalysis. We use solvent-assisted linker exchange reactions to produce a family of UiO-68-TZDC% binary frameworks, which respect the integrity and morphology of the original crystals. Our results suggest that the concentration of TZDC in solution and the reaction time control the distribution of this linker in the sibling crystals for a uniform mixture or the formation of core-shell domains. We also demonstrate how the possibility of generating an asymmetric distribution of both linkers has a negligible effect on the electronic structure and optical band gap of the solids but controls their performance for drastic changes in the photocatalytic activity toward proton or methyl viologen reduction.