Research interest in dynamic assemblies of coordination polymers (CPs) has been rising in recent years for the similarity with life systems in their self-adaptable morphologies and properties. However, monitoring of the assembly process and elucidating the nature for the morphological transformation are very challenging. Here, UV-Vis spectroscopy has been explored as a time-resolved method for monitoring the self-assembly of Au(I)-thiolate CPs in situ. Both step-wise and synergetic effects of the weak interactions in Au(I)-3-mercaptopropionic acid (MPA) CPs, such as H-bonding, coordination bonding, Au(I)-Au(I) interactions and static interactions have been found from the spectral fingerprints, which elucidated the driving forces for the unique morphological transformations from strings to lamellar structures. This work represents a breakthrough in that dynamic self-assembly behaviours can be explained by molecular interactions from molecular level evidences. Based on the spectral fingerprint-structure relationship the reversible and dynamic assembly of Au(I)-MPA CPs can be easily probed.
Homogeneous 2D lamellar assemblies of Au thiolate coordination polymer (ATCP) were obtained by two-ligand co-assembly. The orbital levels and the bandgap of the 2D Au -S network in the centre of the lamellae can be continuously tuned by means of the capping ligands on both sides, to give a new type of inorganic-organic composite semiconductor, the band structure of which can be easily tuned by low-temperature solution-phase co-assembly. Furthermore, the chemical reactivity of these ATCP co-assemblies also proved to be strongly dependent on the organic substituents, with well-tuneable transformation rates to gold nanoparticles. Apparently, this is the first work to demonstrate how organic substituents can continuously tune the electron band structure and chemical reactivity of inorganic atomic layers of semiconductor through co-assembly.
Two pseudopolymorphs are achieved in two solvents and exhibit high structure preservation but have distinct optical properties, morphology and thermal stability.
Photoactive metal−organic frameworks (MOFs) and their derivatives have shown great promise for the degradation of mustard gas and its simulants (e.g., 2-chloroethyl ethyl sulfide or CEES) by selectively oxidizing these toxic organic sulfides to less toxic sulfoxide products under visible or ultraviolet (UV) light. However, these reactions must be conducted in specific solvents (e.g., methanol) to achieve satisfactory selectivity of sulfoxide, which limits the use of MOFs in protective gears. Our mechanistic study shows that during the photooxidation of CEES, the stabilization of a putative persulfoxide intermediate with hydrogen-bond donors was crucial for the formation of sulfoxide. Based on this discovery, we developed a series of MOF/ textile composites containing various hydrogen-bond donor additives for selective photooxidation of organic sulfides under solvent-free conditions. With a 3 mol % catalyst loading, our best-performing composite degraded all CEES within 15 min in oxygen under blue LEDs without solvents, featuring a reaction half-life of 4.4 min and a sulfoxide selectivity of 91%. Under the same condition, the pristine MOF-525 powders only converted 30% CEES after 15 min and showed a 58% sulfoxide selectivity in the final products. Remarkably, this composite also achieved rapid, selective, and solvent-free degradation of CEES utilizing air and simulated sunlight with excellent stability and reusability. This work demonstrates that selective photooxidation of organic sulfides can be achieved without organic solvents under near-practical conditions. The MOF textile composites developed here can be potentially implemented in protective masks and suits against mustard gas.
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