Synthesis, characterization, and polymerization of capped paddlewheel porous cages

A comprehensive review on hydrogen production, storage, and applications

The transformation from combustion-based to renewable energy technologies is of paramount importance due to the rapid depletion of fossil fuels and the dramatic increase in atmospheric CO2 levels resulting from growing global energy demands. To achieve the Paris Agreement's long-term goal of carbon neutrality by 2050, the full implementation of clean and sustainable energy sources is essential. Consequently, there is an urgent demand for zero or low-carbon fuels with high energy density that can produce electricity and heat, power vehicles, and support global trade. This review presents the global motivation to reduce carbon dioxide by utilizing hydrogen technology, which is key to meeting future energy demands. It discusses the basic properties of hydrogen and its application in both prototype and large-scale efficient technologies. Hydrogen is a clean fuel and a versatile energy carrier; when used in fuel cells or combustion devices, the final product is water vapor. Hydrogen gas production methods are reviewed across renewable and non-renewable sources, with reaction processes categorized as green, blue, grey, black, pink, and turquoise, depending on the reaction pathway and CO2 emissions management. This review covers the applications of hydrogen technology in petroleum refining, chemical and metrological production, hydrogen fuel cell electric vehicles (HFCEVs), backup power generation, and its use in transportation, space, and aeronautics. It assesses physical and material-based hydrogen storage methods, evaluating their feasibility, performance, and safety, and comparing HFCEVs with battery and gasoline vehicles from environmental and economic perspectives. Finally, the prospects and challenges associated with hydrogen production, handling, storage, transportation, and safety are also discussed.

Imparting structural robustness of metal-organic cages based on oxo-dimolybdenum clusters

A family of robust and stable molybdenum-based metal-organic cages have been obtained based on the [Mo2O2(μ2-O)2]2+ secondary building unit. The resulting cages are decorated with different pyrdine derivatives that impart structural stability, resulting in the structural elucidation of the activated cage with single-crystal diffraction. The chemical robustness of the cage is also demonstrated by the post-synthetic modification of the cage, which allows the exchange of the pyridine derivatives without rupture of the cage.

Rapid post-synthetic modification of porous coordination cages with copper-catalyzed click chemistry

Novel cobalt calixarene-capped and zirconium-based porous coordination cages were prepared with alkyne and azide functionality to leverage post-synthetic modification by click chemistry. While the calixarene-capped cages showed impressive stability when exposed to the most straightforward copper(I)-catalyzed alkyne-azide cycloaddition (CuAAC) reaction conditions with copper(II) sulfate and sodium ascorbate as the reducing agent, milder reaction conditions were necessary to perform analogous CuAAC reactions on zirconium-based cages. Reaction kinetics were monitored by IR spectroscopy, confirming rapid reaction times (<3 hours).

Strategies for the Construction of Functional Materials Utilizing Presynthesized Metal-Organic Cages (MOCs)

Metal-organic cages (MOCs) that assemble from metal ions or metal clusters and organic ligands have attracted the interest of the scientific community because of their various functional coordination cavities. Unlike metal-organic frameworks (MOFs) with infinite frameworks, MOCs have discrete structures, making them soluble and stable in certain solvents and facilitating their application as starting reagents in the further construction of single components or composite materials. In recent years, increasing progress has been made in this field. In this review, we introduce these works from the perspective of design strategies, and focus on how presynthesized MOCs can be used to construct functional materials. Finally, we discuss the challenges and development prospects in this field.

Post-synthetic modifications of metal–organic cages

Metal-organic cages (MOCs) are discrete, supramolecular entities that consist of metal nodes and organic linkers, which can offer solution processability and high porosity. Thereby, their predesigned structures can undergo post-synthetic modifications (PSMs) to introduce new functional groups and properties by modifying the linker, metal node, pore or surface environment. This Review explores current PSM strategies used for MOCs, including covalent, coordination and noncovalent methods. The effects of newly introduced functional groups or generated complexes upon the PSMs of MOCs are also detailed, such as improving structural stability or endowing desired functionalities. The development of the aforementioned design principles has enabled systematic approaches for the development and characterization of families of MOCs and, thereby, provides insight into structure-function relationships that will guide future developments.

Hierarchical porous metal–organic gels and derived materials: from fundamentals to potential applications

This review summarizes recent progress in the development and applications of metal–organic gels (MOGs) and their hybrids and derivatives dividing them into subclasses and discussing their synthesis, design and structure–property relationship.