Enabling Ethanol Dehydrogenation Catalysis by Postsynthetic Anion Exchange of Triazolate-Based Metal-Organic Frameworks.

Materials containing soft, polarizable elements are expanding the boundaries of catalytic properties, offering unique electronic communication and stability characteristics compared with their harder counterparts due to the enhanced covalent nature of metal-ligand interactions. However, integrating soft components like sulfur into metal-organic frameworks (MOFs) for catalytic applications remains a largely underexplored challenge. Here, we report the synthesis of a family of triazole-based MOFs and expand upon established postsynthetic anion exchange methods to incorporate sterically encumbered polarizable elements, such as alkyl thiolates.

Introducing metal-sulfur active sites in metal-organic frameworks via post-synthetic modification for hydrogenation catalysis.

Metal-sulfur active sites play a central role in catalytic processes such as hydrogenation and dehydrogenation, yet the majority of active sites in these compounds reside on the surfaces and edges of catalyst particles, limiting overall efficiency. Here we present a strategy to embed metal-sulfur active sites into metal-organic frameworks (MOFs) by converting bridging or terminal chloride ligands into hydroxide and subsequently into sulfide groups through post-synthetic modification. We apply this method to two representative MOF families: one featuring one-dimensional metal-chloride chains and another containing discrete multinuclear metal clusters.

Solvent-Directed Assembly of π-Stacked 3D Metal-Organic Frameworks with Tunable Conductivity Enhanced by C Encapsulation.

Metal-organic frameworks (MOFs) with tunable structures and unique host-guest chemistry have emerged as promising candidates for conductive materials. However, the tunability of conductivity and porosity in conductive MOFs, as well as their interrelationship, still lacks a systematic study. Herein, we report the synthesis of a series of 3D copper MOFs (NU-4000 to NU-4003) using a triphenylene-based hexatopic carboxylate linker.

Reticular Structural Diversification of Zirconium Metal-Organic Frameworks Through Angular Ligand Configuration Control.

Reticular chemistry offers practical guidelines for enlarging and enriching the arsenal of metal-organic frameworks (MOFs). However, reticular expansion to access mesoporous structures remains challenging due to limitations in achieving precise control over both the size and configuration during building units' extension. Herein, we combine ligand isomerization and functionalization strategies to regulate the ligand configuration by systematically replacing aryl C-H groups with N atoms, resulting in angular dicarboxylate ligands with various symmetries.

Hydrolytically Stable Phosphonate-Based Metal-Organic Frameworks for Harvesting Water from Low Humidity Air.

Harvesting water from air offers a promising solution to the global water crisis. However, existing sorbents often struggle in arid climates due to limitations such as low sorption capacities, hydrolytic instability, slow mass transport, high desorption enthalpy, and costly operation. Phosphonate-based metal-organic frameworks (MOFs), known for their exceptional water stability, have not been extensively explored for water harvesting.

Single-Crystal X-ray Structures of Homochiral Brønsted Acidic Covalent Organic Frameworks.

Determining the crystal structures of covalent organic frameworks (COFs) with atomic precision is pivotal for uncovering their properties and optimizing functionalities. However, the synthesis of high-quality single crystals of COFs suitable for X-ray diffraction analysis, especially chiral COFs (CCOFs), remains a formidable challenge. In this work, we report two three-dimensional (3D) CCOFs synthesized via imine condensation of tetrahedral tetraamine and tetraaldehydes derived from optically active 1,1'-biphenol phosphoryl chloride or thiophosphoryl chloride.

Exceeding flexpectations: a combined experimental and computational investigation of structural flexibility in 3-dimensional linker-based metal-organic frameworks.

Designing sorbents for the separation of molecules with sub-angstrom differences in size requires precise control over pore size and environment, which can be challenging to establish in the presence of structural flexibility. However, metal-organic frameworks (MOFs) that incorporate 3-dimensional (3D) linkers-ditopic ligands with 3-dimensional, sterically bulky cores-are well-suited to address this challenge, as 3D linkers enable sub-angstrom level control over pore size by mitigating the effects of structural flexibility. In this study, we used a combined computational and experimental approach to quantify flexibility in two systems of MOFs with increasing linker bulkiness, leveraging these systems to distinguish between two classes of flexibility: global and local.

The Last Piece of the Puzzle: Access to 7-Connected Zirconium Metal-Organic Frameworks for Hexane Separation.

Zirconium metal-organic frameworks (Zr-MOFs) exhibit a wide range of Zr cluster connectivities, from 3-connected to 12-connected, enabling diverse structural designs. However, odd-numbered connectivities, especially the 7-connected Zr-MOFs, are exceptionally rare due to geometric symmetry challenges. To address this, we developed a geometric pre-assembly strategy to achieve targeted cluster connectivity.

Lowering Linker Symmetry to Access Zirconium Metal-Organic Frameworks for Inverse Alkane/Alkene Separations.

Enriching the structural diversity of metal-organic frameworks (MOFs) is of great importance in developing functional porous materials with specific properties. New MOF structures can be accessed through the rational design of organic linkers with diverse geometric conformations, and their structural complexity can be enhanced by choosing linkers with reduced symmetry. Herein, a series of Zr-based MOFs with unprecedented topologies were developed through a linker desymmetrization and conformation engineering approach.

Architecting Ultra-Robust Zr(IV) Metal-Organic Framework for Energy-Efficient Desiccant Air Conditioning.

Air-conditioning systems, composed mainly of humidity control and heat reallocation units, play a pivotal role in upholding superior air quality and human well-being across diverse environments ranging from international space stations and pharmacies to granaries and cultural relic preservation sites, and to commercial and residential buildings. The adoption of sorbent water as the working pair and low-grade renewable or waste heat in adsorption-driven air-conditioning presents a state-of-the-art solution, notably for its energy efficiency and eco-friendliness vis-à-vis conventional electricity-driven vapor compression cycles. Here, we introduce a rational π-extension strategy to engineer an ultrarobust and highly porous zirconium metal-organic framework (Zr-MOF).

Leveraging Ligand Desymmetrization to Enrich Structural Diversity of Zirconium Metal-Organic Frameworks for Toxic Chemical Adsorption.

The discovery of metal-organic frameworks (MOFs) with novel structures provides significant opportunities for developing porous solids with new properties and enriching the structural diversity of functional materials for various applications. The rational design of building units with specific geometric conformations is essential to direct the construction of MOFs with unique properties. Herein, we leverage a ligand desymmetrization approach to construct a series of new MOFs.

Integrated CO Capture and Conversion by a Robust Cu(I)-Based Metal-Organic Framework.

Metal-organic frameworks (MOFs) have shown promise in both capturing CO under flue gas conditions and converting it into valuable chemicals. However, the development of a single MOF capable of capturing and selectively converting CO has remained elusive due to a lack of a harmonious combination of selectivity, water stability, and reactivity. For example, Cu(I)-based MOFs are particularly effective for CO conversion, but they do not typically exhibit selective CO adsorption and often suffer from instability in the presence of air and moisture.

Precise Modulation of CO Sorption in TiCe-Oxo Clusters: Elucidating Lewis Acidity of the Ce Metal Sites and Structural Flexibility.

Investigating the structure-property correlation in porous materials is a fundamental and consistent focus in various scientific domains, especially within sorption research. Metal oxide clusters with capping ligands, characterized by intrinsic cavities formed through specific solid-state packing, demonstrate significant potential as versatile platforms for sorption investigations due to their precisely tunable atomic structures and inherent long-range order. This study presents a series of TiCe-oxo clusters with subtle variations in coordinated linkers and explores their sorption behavior.

Programmable Water Sorption through Linker Installation into a Zirconium Metal-Organic Framework.

Hydrolytically stable materials exhibiting a wide range of programmable water sorption behaviors are crucial for on-demand water sorption systems. While notable advancements in employing metal-organic frameworks (MOFs) as promising water adsorbents have been made, developing a robust yet easily tailorable MOF scaffold for specific operational conditions remains a challenge. To address this demand, we employed a topology-guided linker installation strategy using NU-600, which is a zirconium-based MOF (Zr-MOF) that contains three vacant crystallographically defined coordination sites.

Metal-Organic Frameworks as a Tunable Platform to Deconvolute Stereoelectronic Effects on the Catalytic Activity of Thioanisole Oxidation.

The local environment of a metal active site plays an important role in affecting the catalytic activity and selectivity. In recent studies, tailoring the behavior of a molybdenum-based active site modulation of the first coordination sphere has led to improved thioanisole oxidation performance, but disentangling electronic effects from steric influences that arise from these modifications is nontrivial, especially in heterogeneous systems. To this end, the tunability of metal-organic frameworks (MOFs) makes them promising scaffolds for controlling the coordination sphere of a heterogeneous, catalytically active metal site while offering additional attractive features such as crystallinity and high porosity.

Tailoring Hydrophobicity and Pore Environment in Physisorbents for Improved Carbon Dioxide Capture under High Humidity.

CALF-20, a Zn-triazolate-based metal-organic framework (MOF), is one of the most promising adsorbent materials for CO capture. However, competitive adsorption of water severely limits its performance when the relative humidity (RH) exceeds 40%, limiting the potential implementation of CALF-20 in practical settings where CO is saturated with moisture, such as postcombustion flue gas. In this work, three newly designed MOFs related to CALF-20, denoted as NU-220, CALF-20M-w, and CALF-20M-e that feature hydrophobic methyltriazolate linkers, are presented.

Probing Structural Transformations and Degradation Mechanisms by Direct Observation in SIFSIX-3-Ni for Direct Air Capture.

Despite global efforts to reduce carbon dioxide (CO) emissions, continued industrialization threatens to exacerbate climate change. This work investigates methods to capture CO, with a focus on the SIFSIX-3-Ni metal-organic framework (MOF) as a direct air capture (DAC) sorbent. SIFSIX-3-Ni exhibits promising CO adsorption properties but suffers from degradation processes under accelerated aging, which are akin to column regeneration conditions.

Chiral Reticular Chemistry: A Tailored Approach Crafting Highly Porous and Hydrolytically Robust Metal-Organic Frameworks for Intelligent Humidity Control.

Control of humidity within confined spaces is critical for maintaining air quality and human well-being, with implications for environments ranging from international space stations and pharmacies to granaries and cultural relic preservation sites. However, existing techniques rely on energy-intensive electrically driven equipment or complex temperature and humidity control (THC) systems, resulting in imprecision and inconvenience. The development of innovative techniques and materials capable of simultaneously meeting the stringent requirements of practical applications holds the key to creating intelligent and energy-efficient humidity control devices.

Suitability of a diamine functionalized metal-organic framework for direct air capture.

The increase in the atmospheric carbon dioxide level is a significant threat to our planet, and therefore the selective removal of CO from the air is a global concern. Metal-organic frameworks (MOFs) are a class of porous materials that have shown exciting potential as adsorbents for CO capture due to their high surface area and tunable properties. Among several implemented technologies, direct air capture (DAC) using MOFs is a promising strategy for achieving climate targets as it has the potential to actively reduce the atmospheric CO concentration to a safer levels.

Rationally Tailored Mesoporous Hosts for Optimal Protein Encapsulation.

Proteins play important roles in the therapeutic, medical diagnostic, and chemical catalysis industries. However, their potential is often limited by their fragile and dynamic nature outside cellular environments. The encapsulation of proteins in solid materials has been widely pursued as a route to enhance their stability and ease of handling.

Fibrous Zr-MOF Nanozyme Aerogels with Macro-Nanoporous Structure for Enhanced Catalytic Hydrolysis of Organophosphate Toxins.

Metal-organic frameworks (MOFs) with Lewis acid catalytic sites, such as zirconium-based MOFs (Zr-MOFs), comprise a growing class of phosphatase-like nanozymes that can degrade toxic organophosphate pesticides and nerve agents. Rationally engineering and shaping MOFs from as-synthesized powders into hierarchically porous monoliths is essential for their use in emerging applications, such as filters for air and water purification and personal protection gear. However, several challenges still limit the production of practical MOF composites, including the need for sophisticated reaction conditions, low MOF catalyst loadings in the resulting composites, and poor accessibility to MOF-based active sites.