Photoinduced Delamination of Metal–Organic Framework Thin Films by Spatioselective Generation of Reactive Oxygen Species

Abstract

Metal–organic frameworks (MOFs) built from different building units offer functionalities going far beyond gas storage and separation. In connection with advanced applications, e.g., in optoelectronics, hierarchical MOF-on-MOF structures fabricated using sophisticated methodologies have recently become particularly attractive. Here, we demonstrate that the structural complexity of MOF-based architectures can be further increased by employing highly spatioselective photochemistry. Using a layer-by-layer, quasi-epitaxial synthesis method, we realized a photoactive MOF-on-MOF hetero-bilayer consisting of a porphyrinic bottom layer and a tetraphenylethylene (TPE)-based top layer. Illumination of the monolithic thin film with visible light in the presence of oxygen gas results in the generation of reactive oxygen species (1O2) in the porphyrinic bottom layer, which lead to a photocleavage of the TPE units at the internal interface. We demonstrate that this spatioselective photochemistry can be utilized to delaminate the top layers, yielding two-dimensional (2D) MOF sheets with well-defined thickness. Experiments using atomic force microscopy (AFM) demonstrate that these platelets can be transferred onto other substrates, thus opening up the possibility of fabricating planar MOF structures using photolithography.

Reactive oxygen species on transition metal-based catalysts for sustainable environmental applications

“…58,63 Nevertheless, 1 O 2 can be exploited as a moderate oxidant for selective or partial oxidations in chemical synthesis, 43 such as the selective oxidation of various organic substrates including amines, alcohols, olens, and suldes. 31,[64][65][66] Studies have shown that 1 O 2 can oxidize unsaturated organic compounds by electrophilic attack and electron abstraction. For instance, the electrophilic attack of 1 O 2 to dioxin and furan gives endoperoxide intermediates, 67 and the photosensitized oxygenation of phenol proceeds via hydrogen abstraction by 1 O 2 .…”

Recent progress in strategies for preparation of metal-organic frameworks and their hybrids with different dimensions

“…The substrates were then alternately immersed in the two ethanol solutions for 20 cycles, resulting in the synthesis of highly crystalline films [Figure 15A]. Xiao et al constructed ultrathin TA-Zn 2+ layers based on tannic acid (TA) and Zn 2+ on polyethersulfone substrates using the LBL method, and subsequently converted the TA-Zn 2+ layers into ZIF-8 films by immersing them in the 2-methylimidazole (Hmim) solution as a zinc source [216] . The LBL method has also been applied to heteroepitaxy and Liu et al have reported the use of the LBL method to fabricate a photoactive MOF-on-MOF heterostructure [217] .…”

Spectroscopic Investigation of Bianthryl‐Based Metal–Organic Framework Thin Films and Their Photoinduced Topotactic Transformation

“…[ 26–29 ] Instead of electronic excitation, absorption of light can also lead to chemical changes under ambient condition. [ 30–33 ] So far, the photochemistry of MOFs and SURMOFs has received only little attention. In particular, in the presence of ambient O 2 and moisture (H 2 O) photoexcitation can lead to new chemical product formation, which may change the photophysical properties of the chromophoric MOF under investigation.…”

“…[26][27][28][29] Instead of electronic excitation, absorption of light can also lead to chemical changes under ambient condition. [30][31][32][33] So far, the photochemistry of MOFs and SURMOFs has received only little attention. In particular, in the presence of ambient Metal-organic frameworks (MOFs) have gained a large amount of interest because of their periodic and modular structure.…”