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Highly porous polymer beads coated with nanometer-thick metal oxide films for photocatalytic oxidation of bisphenol A
Gergő Ballai, Tomaž Kotnik, Matjaž Finšgar, Albin Pintar, Zoltán Kónya, András Sápi, Sebastijan Kovačič, 2023, original scientific article

Abstract: Highly porous metal oxide−polymer nanocomposites are attracting considerable interest due to their unique structural and functional features. A porous polymer matrix brings properties such as high porosity and permeability, while the metal oxide phase adds functionality. For the metal oxide phase to perform its function, it must be fully accessible, and this is possible only at the pore surface, but functioning surfaces require controlled engineering, which remains a challenge. Here, highly porous nanocomposite beads based on thin metal oxide nanocoatings and polymerized high internal phase emulsions (polyHIPEs) are demonstrated. By leveraging the unique properties of polyHIPEs, i.e., a three-dimensional (3D) interconnected network of macropores, and high-precision of the atomic-layer-deposition technique (ALD), we were able to homogeneously coat the entire surface of the pores in polyHIPE beads with TiO$_2$-, ZnO-, and Al$_2$O$_3$-based nanocoatings. Parameters such as nanocoating thickness, growth per cycle (GPC), and metal oxide (MO) composition were systematically controlled by varying the number of deposition cycles and dosing time under specific process conditions. The combination of polyHIPE structure and ALD technique proved advantageous, as MO-nanocoatings with thicknesses between 11 ± 3 and 40 ± 9 nm for TiO$_2$ or 31 ± 6 and 74 ± 28 nm for ZnO and Al$_2$O$_3$, respectively, were successfully fabricated. It has been shown that the number of ALD cycles affects both the thickness and crystallinity of the MO nanocoatings. Finally, the potential of ALD-derived TiO$_2$-polyHIPE beads in photocatalytic oxidation of an aqueous bisphenol A (BPA) solution was demonstrated. The beads exhibited about five times higher activity than nanocomposite beads prepared by the conventional (Pickering) method. Such ALD-derived polyHIPE nanocomposites could find wide application in nanotechnology, sensor development, or catalysis.
Keywords: nanovlakna, aerosoli, filtracija, emulsion-templating, macroporous polymers, atomic-layer-deposition
Published in DKUM: 15.04.2024; Views: 249; Downloads: 17
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Sustainable in-water synthesis of aliphatic porous polyazines : a versatile platform for conjugated aerogels, polyHIPEs, or carbon foams
Tomaž Kotnik, Gregor Žerjav, Zoran Novak, Albin Pintar, Sebastijan Kovačič, 2023, original scientific article

Abstract: Access to conjugated porous polymers via synthetically sustainable and straightforward routes is highly desirable, as many polymer systems exhibit high performance but require arduous synthetic protocols that rarely pave the way to commercial reality. In this article, we describe an easily fabricated series of novel highly porous poly(Schiff bases) that feature an aliphatic conjugated backbone obtained with low synthetic complexity from simple reagents such as glyoxal and hydrazine monohydrate in water. The effective synthesis enables the preparation of three different functional scaffolds, i.e., aerogels, polyHIPEs (polymerized HIPEs), and even carbon foams from aliphatic poly(azine) (PAZ) networks. The reported synthetic approach is compared to the literature using ″green chemistry metrics″, such as the E-factor and synthetic complexity (SC) index, and shows dramatic improvements. An E-factor of up to 0.27 for aerogels or 80 for polyHIPEs and an SC index of 2.7 are much lower than those for poly(arylene)-based conjugated analogues, indicating good scalability, sustainability, and low cost. PAZ materials feature impressive red/near IR-shifted optical absorption band edges, with an electrochemical band gap of 1.45 eV. Aliphatic PAZ scaffolds are characterized by high flexibility compared to aromatic analogues and do not fail at compressive loads of up to 70%. Finally, carbonization at 500 °C leads to highly porous carbonaceous scaffolds with a high N content of up to 29 wt % (21 mmol of nitrogen per gram carbon material).
Published in DKUM: 13.03.2024; Views: 696; Downloads: 17
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