Eva Meeus opened discussion of the paper by Helma Wennemers: I was wondering whether you could "revert" this process? More specifically, can you equip your peptide-based template to enable length-controlled scissions of oligomers to facilitate, for example, monomer recycling? Helma Wennemers answered: Yes, this i
Substrate accessibility is a key limiting factor for the efficiency of heterogeneous photoredox catalysis. Recently, a high photoactive surface area of conjugated microporous polymer nanoparticles (CMP NPs) has made them promising candidates for overcoming the mass transfer limitation to achieve high photocatalytic efficiency. However, this potential has not been realized due to limited dispersibility of CMP NPs in many solvents, particularly in water. Here, we report a polymer grafting strategy that furnishes versatile hairy CMP NPs with enhanced solvent-specific dispersibility. The method associates hundreds of solvent-miscible repeating units with one chain end of the photocatalyst surface, allowing minimal modification to the CMP network that preserves its photocatalytic activity. Therefore, the enhanced dispersibility of hairy CMP NPs in organic solvents or aqueous solutions affords high efficiency in various photocatalytic organic transformations.
Abstract Pseudohomogene polymere Photokatalysatoren sind eine neue Klasse hocheffizienter und einstellbarer photokatalytischer Materialien, bei denen die photokatalytischen Zentren leicht zugänglich sind. Die Schaffung hocheffizienter photokatalytischer Materialien, die schnell abgetrennt und zurückgewonnen werden können, ist eine der entscheidenden Herausforderungen in der photokatalytischen Chemie. Hier beschreiben wir auf den pH‐Wert reagierende photokatalytische Nanopartikel, die unter sauren Bedingungen aktiv und gut dispergiert sind, aber bei Erhöhung des pH‐Werts sofort aggregieren und so eine einfache Rückgewinnung ermöglichen. Diese auf den pH‐Wert reagierenden photokatalytischen Polymere können für verschiedene photokatalytische Umwandlungen verwendet werden, darunter die Reduktion von Cr VI und die Photoredoxalkylierung von Indolderivaten. Insbesondere beschleunigt die kationische Natur des Photokatalysators die Reaktionsgeschwindigkeit eines anionischen Substrats im Vergleich zu ungeladenen Spezies. Diese photokatalytischen Partikel können leicht recycelt werden und ermöglichen mehrere aufeinanderfolgende photokatalytische Reaktionen ohne deutlichen Aktivitätsverlust.
Abstract Investigations into the selective oxidation of inert sp 3 C−H bonds using polymer photocatalysts under mild conditions have been limited. Additionally, the structure‐activity relationship of photocatalysts often remains insufficiently explored. Here, a series of thiophene‐based covalent triazine frameworks (CTFs) are used for the efficient and selective oxidation of hydrocarbons to aldehydes or ketones under ambient aerobic conditions. Spectroscopic methods conducted in situ and density functional theory (DFT) calculations revealed that the sulfur atoms within the thiophene units play a pivotal role as oxidation sites due to the generation of photogenerated holes. The effect of photogenerated holes on photocatalytic toluene oxidation was investigated by varying the length of the spacer in a CTF donor‐acceptor based photocatalyst. Furthermore, the manipulation of reactive oxygen species was employed to enhance selectivity by weakening the peroxidative capacity. As an illustrative example, this study successfully demonstrated the synthesis of a precursor of the neurological drug AMG‐579 using a photocatalytic protocol.
DNA-polymer hybrids have been attracting interest as adaptable functional materials by combining the stability of polymers with DNA nanotechnology. Both research fields have in common the capacity to be precise, versatile, and tunable, a prerequisite for creating powerful tools which can be easily tailored and adapted for bio-related applications. However, the conjugation of hydrophilic DNA with hydrophobic polymers remains challenging. In recent years, polymerization-induced self-assembly (PISA) has attracted significant attention for constructing nano-objects of various morphologies owing to the one-step nature of the process, creating a beneficial method for the creation of amphiphilic DNA-polymer nanostructures. This process not only allows pure DNA-polymer-based systems to be produced but also enables the mixture of other polymeric species with DNA conjugates. Here, we present the first report of a DNA-PEG corona nano-object's synthesis without the addition of an external photoinitiator or photocatalyst via photo-PISA. Furthermore, this work shows the use of DNA-macroCTA, which was first synthesized using a solid-support method resulting in high yields, easy upscaling, and no need for HPLC purification. In addition, to the formation of DNA-polymer structures, increasing the nucleic acid loading of assemblies is of great importance. One of the most intriguing phenomena of DNA is the hybridization of single-stranded DNA with a second strand, increasing the nucleic acid content. However, hybridization of DNA in a particle corona may destabilize the nanomaterial due to the electrostatic repulsive force on the DNA corona. Here, we have investigated how changing the DNA volume fraction in hybrid DNA-polymer self-assembled material affects the morphology. Moreover, the effect of the corona composition on the stability of the system during the hybridization was studied. Additionally, the hybridization chain reaction was successfully applied as a new method to increase the amount of DNA on a DNA-based nano-object without disturbing the morphology achieving a fluorescence signal amplification.
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