As an emerging class of porous crystalline materials, covalent organic frameworks (COFs) are excellent candidates for various applications. In particular, they can serve as ideal platforms for capturing CO₂ to mitigate the dilemma caused by the greenhouse effect. Recent research achievements using COFs for CO₂ capture are highlighted. A background overview is provided, consisting of a brief statement on the current CO₂ issue, a summary of representative materials utilized for CO₂ capture, and an introduction to COFs. Research progresses on: i) experimental CO₂ capture using different COFs synthesized based on different covalent bond formations, and ii) computational simulation results of such porous materials on CO₂ capture are summarized. Based on these experimental and theoretical studies, careful analyses and discussions in terms of the COF stability, low- and high-pressure CO₂ uptake, CO₂ selectivity, breakthrough performance, and CO₂ capture conditions are provided. Finally, a perspective and conclusion section of COFs for CO₂ capture is presented. Recent advancements in the field are highlighted and the strategies and principals involved are discussed.

Replacing the rare and precious platinum (Pt) electrocatalysts with earth-abundant materials for promoting the oxygen reduction reaction (ORR) at the cathode of fuel cells is of great interest in developing high-performance sustainable energy devices. However, the challenging issues associated with non-Pt materials are still their low intrinsic catalytic activity, limited active sites, and the poor mass transport properties. Recent advances in material sciences and nanotechnology enable rational design of new earth-abundant materials with optimized composition and fine nanostructure, providing new opportunities for enhancing ORR performance at the molecular level. This Review highlights recent breakthroughs in engineering nanocatalysts based on the earth-abundant materials for boosting ORR.

An emerging class of porous materials known as metal–organic gels (MOGs) has been gaining popularity due to their stability under reduced pressure and sensitivity to varying chemical environment. In this work, MOGs were used for the storage and controlled release of an anticancer drug, doxorubicin (Dox). In acidic pH or high concentration of glutathione, significant release of Dox from Dox-loaded MOGs was observed. In addition, structural integrity of MOGs was disrupted in an acidic or glutathione-containing environment, which was demonstrated by several characterization techniques. In vitro experiments on HeLa cancer cells showed the low toxicity of MOGs and further confirmed triggered drug release of Dox-loaded MOGs. Based on the promising results obtained, Dox-loaded MOGs present a great potential for future drug delivery applications.

Der Ersatz von Platin (Pt) durch billigere, unedle Elemente in Elektrokatalysatoren für die Sauerstoffreduktionsreaktion (ORR) ist für die Entwicklung nachhaltiger, leistungsfähiger Brennstoffzellen zur Energieumwandlung von größtem Interesse. Platinfreie Materialien bergen jedoch eine Reihe von Herausforderungen, wie eine geringe intrinsische katalytische Aktivität, eine begrenzte Zahl aktiver Zentren und schlechte Stofftransporteigenschaften. Jüngste Fortschritte in den Materialwissenschaften und der Nanotechnologie ermöglichen nun ein rationales Design von neuen Materialien mit unedlen Elementen mit optimierter Zusammensetzung und präziser Nanostruktur. Dies eröffnet neue Möglichkeiten zur Verbesserung der ORR-Leistung auf molekularer Ebene. Dieser Aufsatz beleuchtet die aktuellen Durchbrüche bei der Entwicklung von Nanokatalysatoren für die ORR.

An imine-based nitrogen-rich covalent-organic framework (COF) was successfully synthesized using two triangular building units under solvothermal reaction condition. The gas adsorption properties of the obtained microporous nitrogen-rich COF were investigated. The results indicated that the activated COF material presented good up take capabilities of CO₂ and CH₄ at 61.2 and 43.4 cm³·g⁻¹ at 1 atm and 273 K, respectively, showing its application potential in selective gas capture and separation.

Three highly porous metal–organic frameworks (MOFs) with a uniform rht-type topological network but hierarchical pores were successfully constructed by the assembly of triazole-containing dendritic hexacarboxylate ligands with Zn^II ions. These transparent MOF crystals present gradually increasing pore sizes upon extension of the length of the organic backbone, as clearly identified by structural analysis and gas-adsorption experiments. The inherent accessibility of the pores to large molecules endows these materials with unique properties for the uptake of large guest molecules. The visible selective adsorption of dye molecules makes these MOFs highly promising porous materials for pore-size-dependent large-molecule capture and separation.

Interpenetrated metal–organic frameworks (MOFs) are often observed to show lower porosity than their non-interpenetrating analogues. It would be highly desirable if the interpenetrated MOFs could still provide high stability, high rigidity, and optimal pore size for applications. In this work, an asymmetrical tricarboxylate organic linker was rationally designed for the construction of a copper(II)-based microporous MOF with a twofold interpenetrated structure of Pt₃O₄ topology. In spite of having structural interpenetration, the activated MOF shows high porosity with a Brunauer–Emmett–Teller surface area of 2297 m² g⁻¹, and high CO₂ (15.7 wt % at 273 K and 1 bar) and H₂ uptake (1.64 wt % at 77 K and 1 bar).

Covalent organic frameworks (COFs) are periodic two- or three-dimensional polymeric networks with high surface areas, low density, and designed structures. Because COFs are normally prepared based on reversible formation of covalent bonds with relatively weak stability, their structures can be easily broken or damaged due to changes in the surrounding environment. Thus, developing strategies to realize the reconstruction of COFs in order to extend their usage lifetime is crucial for practical applications. In addition, exploring the kinetics of COF growth under varied reaction conditions is important for better understanding the nucleation and growth processes of COFs. In this work, the reformation mechanism of an imine-based COF using an ex situ characterization method was investigated, disclosing an interesting COF reconstruction progress from disorder to order. The present study shows the regeneration ability of COFs, and the developed method could be generalized for broader use in the field.

Three highly porous metal–organic frameworks (MOFs) with a uniform rht-type topological network but hierarchical pores were successfully constructed by the assembly of triazole-containing dendritic hexacarboxylate ligands with Zn^II ions. These transparent MOF crystals present gradually increasing pore sizes upon extension of the length of the organic backbone, as clearly identified by structural analysis and gas-adsorption experiments. The inherent accessibility of the pores to large molecules endows these materials with unique properties for the uptake of large guest molecules. The visible selective adsorption of dye molecules makes these MOFs highly promising porous materials for pore-size-dependent large-molecule capture and separation.

Three types of zeolitic imidazolate frameworks (ZIFs) with different topological structures and functional imidazolate-derived ligands, namely, ZIF-8, ZIF-68, and ZIF69, have been directly carbonized to prepare porous carbon materials at 1000 °C. These as-synthesized porous carbon materials were activated with fused KOH to increase their surface areas and pore volumes for use in gas storage and supercapacitors. The relationship between the local structure of the products and the composition of the precursors has been investigated in detail. The BET surface areas of the resultant activated carbon materials are 2437 (CZIF8a), 1861 (CZIF68a), and 2264 m² g⁻¹ (CZIF69a). CZIF8a exhibits the highest H₂-storage capacities of 2.59 wt. % at 1 atm and 77 K, whereas CZIF69a has the highest CO₂ uptake of 4.76 mmol g⁻¹ at 1 atm and 273 K, owing to its local structure and pore chemical environment. The specific capacities are calculated from the CV curves. CZIF69a exhibits the highest supercapacitor performance of 168 F g⁻¹ at a scan speed of 5 mV s⁻¹. These results indicate that the functional chloride group on the benzimidazolate ligand plays a very important role in improving the surface area, pore volume, and, therefore, CO₂-capture and supercapacitor properties of the corresponding porous carbon materials.