03 Fakultät Chemie

Permanent URI for this collectionhttps://elib.uni-stuttgart.de/handle/11682/4

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Institute: search.filters.UBSInstitut.Max-Planck-Institut für FestkörperforschungInstitute: search.filters.UBSInstitut.Fakultätsübergreifend / Sonstige EinrichtungInstitute: search.filters.UBSInstitut.Fakultät Chemie (Institutsübergreifend)

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    Designing covalent organic framework‐based light‐driven microswimmers toward therapeutic applications
    (2023) Sridhar, Varun; Yildiz, Erdost; Rodríguez‐Camargo, Andrés; Lyu, Xianglong; Yao, Liang; Wrede, Paul; Aghakhani, Amirreza; Akolpoglu, Birgul M.; Podjaski, Filip; Lotsch, Bettina V.; Sitti, Metin
    While micromachines with tailored functionalities enable therapeutic applications in biological environments, their controlled motion and targeted drug delivery in biological media require sophisticated designs for practical applications. Covalent organic frameworks (COFs), a new generation of crystalline and nanoporous polymers, offer new perspectives for light‐driven microswimmers in heterogeneous biological environments including intraocular fluids, thus setting the stage for biomedical applications such as retinal drug delivery. Two different types of COFs, uniformly spherical TABP‐PDA‐COF sub‐micrometer particles and texturally nanoporous, micrometer‐sized TpAzo‐COF particles are described and compared as light‐driven microrobots. They can be used as highly efficient visible‐light‐driven drug carriers in aqueous ionic and cellular media. Their absorption ranging down to red light enables phototaxis even in deeper and viscous biological media, while the organic nature of COFs ensures their biocompatibility. Their inherently porous structures with ≈2.6  and ≈3.4 nm pores, and large surface areas allow for targeted and efficient drug loading even for insoluble drugs, which can be released on demand. Additionally, indocyanine green (ICG) dye loading in the pores enables photoacoustic imaging, optical coherence tomography, and hyperthermia in operando conditions. This real‐time visualization of the drug‐loaded COF microswimmers enables unique insights into the action of photoactive porous drug carriers for therapeutic applications.
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    Shedding light on the active species in a cobalt‐based covalent organic framework for the electrochemical oxygen evolution reaction
    (2024) Hosseini, Pouya; Rodríguez‐Camargo, Andrés; Jiang, Yiqun; Zhang, Siyuan; Scheu, Christina; Yao, Liang; Lotsch, Bettina V.; Tschulik, Kristina
    While considerable efforts have been devoted to developing functionalized covalent organic frameworks (COFs) as oxygen evolution electrocatalysts in recent years, studies related to the investigation of the true catalytically active species for the oxygen evolution reaction (OER) remain lacking in the field. In this work, the active species of a cobalt‐functionalized COF (TpBpy‐Co) is studied as electrochemical OER catalyst through a series of electrochemical measurements and post‐electrolysis characterizations. These results suggest that cobalt oxide‐based nanoparticles are formed in TpBpy‐Co from Co(II) ions coordinated to the COF backbone when exposing TpBpy‐Co to alkaline media, and these newly formed nanoparticles serve as the primary active species for oxygen evolution. The study thus emphasizes that caution is warranted when assessing the catalytic activity of COF electrocatalysts, as the pristine COF may act as the pre‐catalyst, with the active species forming only under catalyst operating conditions. Specifically, strong coordination between COFs and metal centers under electrochemical operation conditions is crucial to avoid unintended transformation of COF electrocatalysts. This work thus contributes to the rational development of earth‐abundant COF OER catalysts for the production of green hydrogen from renewable resources.