Structural Transformation in Metal–Organic Frameworks for Reversible Binding of Oxygen

Abstract

Polycyclic aromatic derivatives can trap 1 O 2 to form endoperoxides (EPOs) for O 2 storage and as sources of reactive oxygen species.H owever,t hese materials suffer from structural amorphism, which limit both practical applications and fundamental studies on their structural optimization for O 2 capture and release.Metal-organic frameworks (MOFs) offer advantages in O 2 binding,such as clear structure-performance relationships and precise controllability.Herein, we report the reversible binding of O 2 is realized via the chemical transformation between anthracene-based and the corresponding EPO-based MOF.Itisshown that anthracene-based MOF,the framework featuring linkers with polycyclic aromatic structure,c an rapidly trap 1 O 2 to form EPOs and can be restored upon UV irradiation or heating to release O 2 .Furthermore,we confirm that photosensitizer-incorporated anthracene-based MOF are promising candidates for reversible O 2 carriers controlled by switching Vis/UV irradiation.Endoperoxides (EPOs) have interesting photochemical and thermodynamic properties. [1] Their potential applications for reversible oxygen storage and as chemical sources of reactive oxygen species,h ave made these compounds the focus of many fundamental investigations. [2] Many polycyclic aromatic derivatives could trap the singlet oxygen ( 1 O 2 )t of orm EPOs. [3] EPOs exhibit the exceptional performance of releasing oxygen, generally in the excited singlet state, under heating or ultra violet (UV) irradiation. [4] Functional materials constructed with polycyclic aromatic compounds or EPOs can conduct the binding of oxygen upon light irradiation or with thermal treatment. [5] Therefore,t he reversible chemical binding of oxygen has significant advantages,such as better stability and more controllability,c ompared with physical adsorption. [6] However,t hese materials suffer from structural amorphism and poor solubility,w hich limit both practical applications and fundamental studies on their structural optimization for the precise control of O 2 capture and release.Metal-organic frameworks (MOFs) are porous crystalline materials and used extensively for aw ide range of applications from basic research to practical utilizations,i ncluding adsorption and separation of guest molecules,p roviding active catalytic sites and fabrication of drug delivery systems. [7] Theh ybrid nature of MOF offers an almost infinite suite of building blocks that can be manipulated to construct functional MOF through introducing open metal coordinate sites and functional groups into the framework. [8] Generally, the chemical transformation of building blocks in MOF involves irreversible or passive interaction, which may lead to the damage of crystalline structure. [9] It is difficult to control the spatial configuration transformation of linkers and the structure stability of MOF,t hus,t he chemistry occurring at the interface between the framework and an incoming substrate. [10] To our best knowledge,t he reversible binding of guest molecule triggered by th...

Peripheral RAFT Polymerization on a Covalent Organic Polymer with Enhanced Aqueous Compatibility for Controlled Generation of Singlet Oxygen

“…To name a few, the photothermal effects of gold nanorods and organic small molecules have been exploited to trigger the controlled release of 1 O 2 from EPO‐containing compounds. Chemical species and UV irradiation have also been explored as stimuli for controlled 1 O 2 liberation . However, to the best of our knowledge, the design and fabrication of COPs with polyaromatic derivatives for reversible binding of oxygen has not been reported.…”

“…Chemical species and UV irradiation have also been explored as stimuli for controlled 1 O 2 liberation. [17,18] However, to the best of our knowledge, the design and fabrication of COPs with polyaromatic derivatives for reversible binding of oxygen has not been reported. Moreover, the poor solubility of COPs in common solvents including water has confined COPs as heterogeneous reactants/catalysts.…”

3D Covalent Organic Frameworks Based on Polycyclic Aromatic Hydrocarbons for Reversible Oxygen Capture

“…[ 4 ] Among the chemical sources of 1 O 2 , endoperoxides (EPOs) can be used as molecular carriers to reversibly stimulate the singlet state to release oxygen by heating or UV irradiation. [ 5 ] Compared with other chemical sources (such as the H 2 O 2 /MoO 4 − system), EPOs can release oxygen cleanly without residual oxidizing agents, which is not limited to aqueous media. [ 6 ] In addition, the reversible chemical binding of oxygen in EPOs has significant advantages in comparison with physical adsorption, such as better stability and stronger controllability.…”

“…However, the structural amorphousness and poor solubility of these materials limit the practical application and basic research on functional materials to precisely control 1 O 2 capture and release. [ 5 ] To overcome these issues, 1 O 2 delivery systems based on nanocarriers, such as gold nanorods, [ 7 ] supramolecular polymers, [ 8 ] metal–organic frameworks (MOFs), [ 9 ] and covalent organic polymers (COPs), [ 10,11 ] have been developed in recent years. In particular, some porphyrin‐based MOFs or COPs [ 12 ] were used as photosensitizers for photodynamic cancer therapy owing to their larger molecular size and extensive π‐conjugated systems.…”

Exciton Coupling and Conformational Changes Impacting the Excited State Properties of Metal Organic Frameworks

“…The carboxylic acid groups allow the connection to metal nodes as a prerequisite for the formation of a MOF, while the core of the molecule consists of the widely used fluorescence standard 9,10-diphenylanthracene (DPA) [ 41 , 42 ], which serves as a prototypical example for a π-conjugated, acene-based dye [ 43 , 44 , 45 , 46 ]. The first excited state of DPA is known to have a long lifetime and high quantum yield, making ADB-linked systems an interesting choice for studies of the optical properties of MOFs [ 47 , 48 ].…”