Macrocycle‐Based Covalent Organic Frameworks

Abstract

Macrocycles with well‐defined cavities and the ability to undergo supramolecular interactions are classical materials that have played an essential role in materials science. However, one of the most substantial barriers limiting the utilization of macrocycles is their aggregation, which blocks the active regions. Among many attempted strategies to prevent such aggregation, installing macrocycles into covalent organic frameworks (COFs), which are porous and stable reticular networks, has emerged as an ideal solution. The resulting macrocycle‐based COFs (M‐COFs) preserve the macrocycles’ unique activities, enabling applications in various fields such as single‐atom catalysis, adsorption/separation, optoelectronics, phototherapy, and structural design of forming single‐layered or mechanically interlocked COFs. The resulting properties are unmatchable by any combination of macrocycles with other substrates, opening a new chapter in advanced materials. This review focuses on the latest progress in the concepts, synthesis, properties, and applications of M‐COFs, and presents an in‐depth outlook on the challenges and opportunities in this emerging field.

Regulation of Redox Molecular Junctions in Covalent Organic Frameworks for H2O2 Photosynthesis Coupled with Biomass Valorization

“…The decomposition products are 18 O 2 and 16 O 2 , in which 18 O 2 accounts for the majority and shows that H 2 O 2 is produced mainly through the ORR process by Cu 3 -BT-COF (Figure 3f). Interestingly, a small amount of H 2 O 2 can still be produced by the WOR process, as certified by the detection of trace 16 O 2 from the decomposed H 2 O 2 in the isotope experiment, which indicates it to be a competitive reaction between FFA photooxidation and WOR, and the dominate role of FFA photooxidation for the half reaction. Besides, the apparent quantum yield (AQY) between 420 nm is 7.98 % with a solar chemical conversion (SCC) efficiency of 0.62 %, which are much higher than the full reaction photosynthesis of H 2 O 2 (AQY, 3.72 % and SCC, 0.28 %).…”

“…In addition, 18 O 2 isotope experiments have been carried out to verify the ORR process for H 2 O 2 photosynthesis (Figure 3f). Cu 3 -BT-COF is illuminated in H 2 16 O and 18 O 2 gas for 4 h. After removing the unreacted gas with Ar gas, MnO 2 is added to the reaction system to decompose H 2 O 2 and release O 2 . The escaped gas is analyzed by gas chromatography-mass spectrometry.…”

“…Covalent organic frameworks (COFs), composed of light-weight elements and linked by covalent bonds, present crystalline structures, tunable functionality, high stability and porosity, etc. [16] Recently, metal cluster-based COFs (MCOFs), a kind of attractive COF obtained through the covalent connection between metal clusters and organic molecules, [17] have shown high promise in many applications like CO 2 photo-reduction, [18] photocatalytic cycloaddition of CO 2 , [19] or photo-oxidation of biomass, [17c] etc. Specifically, the pre-designable metal clusters can be covalently connected with organic linkers to endow MCOFs with intrinsic properties and might be applied as potential photocatalysts for H 2 O 2 photosynthesis coupled with FFA photo-oxidation owing to the following reasons: i) compared with other materials with higher density, MCOFs with low density and high porosity might provide more exposed surface area and active sites that can be assessable for the substrates; [17d] ii) the tunable structures with functional struts endow MCOFs with an efficient metal-ligand charge transfer (MLCT) effect to realize efficient separation of electrons and holes to accomplish the coupled reaction [20] and iii) MCOFs with crystalline and well-defined structures are conducive to mechanism study.…”

Regulation of Redox Molecular Junctions in Covalent Organic Frameworks for H2O2 Photosynthesis Coupled with Biomass Valorization

“…Covalent organic frameworks (COFs), composed of light-weight elements and linked by covalent bonds, present crystalline structures, tunable functionality, high stability and porosity, etc. [16] Recently, metal cluster-based COFs (MCOFs), a kind of attractive COF obtained through the covalent connection between metal clusters and organic molecules, [17] have shown high promise in many applications like CO 2 photo-reduction, [18] photocatalytic cycloaddition of CO 2 , [19] or photo-oxidation of biomass, [17c] etc. Specifically, the pre-designable metal clusters can be covalently connected with organic linkers to endow MCOFs with intrinsic properties and might be applied as potential photocatalysts for H 2 O 2 photosynthesis coupled with FFA photo-oxidation owing to the following reasons: i) compared with other materials with higher density, MCOFs with low density and high porosity might provide more exposed surface area and active sites that can be assessable for the substrates; [17d] ii) the tunable structures with functional struts endow MCOFs with an efficient metal-ligand charge transfer (MLCT) effect to realize efficient separation of electrons and holes to accomplish the coupled reaction [20] and iii) MCOFs with crystalline and well-defined structures are conducive to mechanism study.…”

Methylene-bridged naphthotubes: new macrocyclic arenes with great potential for supramolecular chemistry

“…47,48 Besides classic macrocyclic arenes such as CAs and PAs, various types of macrocyclic arenes with novel structures have been synthesized and reported with the rapid evolution of supramolecular chemistry. 49 These macrocyclic arenes display intriguing properties and applications, greatly enriching the toolbox of supramolecular chemistry. 50 Biphenarenes are a class of macrocycles with customizable skeletons and cavity sizes prepared by Li and co-workers in 2015.…”