Soft-templated synthesis of π-conjugated porous polymer scaffolds for visible-light-driven heterogeneous photocatalysis

Kotnik, Tomaž (author), Kovačič, Sebastijan (mentor), Košmrlj, Janez (comentor)

Conjugated polymers have proven essential in a variety of fields, including organic electronics, catalysis, and energy harvesting and storage. Their semiconducting properties, which arise from extended conjugation in the polymer backbone, are crucial for these applications. Given their immense technological potential, there is a significant drive to develop more efficient conjugated polymers. This is typically achieved by optimizing their molecular structure, as it directly influences their energy levels and redox potentials. The current synthesis of conjugated polymers largely depends on transition-metal-catalysed reactions, such as Kumada, Suzuki–Miyaura, and Sonogashira–Hagihara couplings. This reliance poses a barrier to the widespread adoption of conjugated polymers due to potential residual metal impurities. Moreover, residual metal impurities can cause changes to material's optoelectronic/photophysical properties and hinder its application. Thus, there is a significant demand for synthesis techniques that eliminate the use of transition metals or transmetalating agents. In this PhD thesis, we combine transition-metal-free reactions with soft-templating techniques, namely high internal phase emulsion and foams, and thereby produce π-conjugated porous polymers. We developed a new oil-in-oil-in-oil double emulsion system which allows the use of water-sensitive reactions, such as Knoevenagel and Schiff-base polycondensation to produce cyanovinylene-, imine- and azine-linked π-conjugated polyHIPEs in various shapes. Additionally, we redefined the Staudinger reaction conditions, allowing the synthesis of a wide variety of poly(arylene iminophosphorane)s. We uncovered the oxidation mechanism of phosphine end-groups, which had previously hindered polymerization attempts. Furthermore, we utilized nitrogen gas formation during the Staudinger reaction as a gaseous template to produce π-conjugated foams. Synthesized conjugated porous polymers were investigated for the photocatalytic degradation of organic pollutants in water, as well as for some tailored photosynthetic applications. Materials showed promising results in degrading model pollutants bisphenol A and aniline as well as showed high catalytic activity for the photosulphoxidation of thioanisol.

• Language: English
• Keywords: -
• Work type: Doctoral dissertation
• Typology: 2.08 - Doctoral Dissertation
• Organization: FKKT - Faculty of Chemistry and Chemical Technology
• Year: 2024
• PID: 20.500.12556/RUL-164309
• COBISS.SI-ID: 219607811
• Publication date in RUL: 21.10.2024

Secondary language

• Language: Slovenian
• Title: Sinteza π-konjugiranih poroznih polimernih ogrodij z uporabo mehkih šablon za namen heterogene fotokatalize v področju vidne svetlobe

Abstract

Konjugirani polimeri so se uveljavili kot visokopotencialni materiali na različnih področjih, vključno z elektroniko, katalizo, ter za pridobivanje in shranjevanje energije. Polprevodne lastnosti, ki izhajajo iz podaljšane konjugacije, so bistvene za večino omenjenih aplikacij. Molekularna struktura konjugiranih polimerov je ključnega pomena, saj v veliki meri določa energijske nivoje makromolekul, kot tudi redoks potenciale. Sinteza konjugiranih polimerov v veliki meri temelji na reakcijah kataliziranih s kovinami prehoda, kot so Kumada, Suzuki-Miyaura in Sonogashira-Hagihara reakcije. Kovinske zvrsti lahko ostanejo kot nečistote v končnem materialu, ter spremenijo optoelektronske in fotofizikalne lastnosti in tako vplivajo na končno aplikacijo. Posledično obstaja velika težnja po sintetskih pristopih, ki ne vključujejo kovin prehoda. V doktorski disertaciji smo združili polimerizacijske reakcije brez kovinskih katalizatorjev ter mehke šablone, natančneje emulzije z visokim deležem interne faze in pene, ter tako pripravili π-konjugirane porozne polimere. Razvili smo nov sistem dvojne emulzije olje-v-olje-v-olje, ki je sestavljen iz DMF, petrol benzina in prafinskega/silikonskega olja. Slednji je omogočil uporabo na vodo občutljivih reakcij, kot so Knoevenagelova in Schiffova bazna polikondenzacija za pripravo π-konjugiranih poliHIPE materilov povezanih z ciano-vinilenskimi, iminkimi ali azinskimi mostički. Prav tako smo revizirali pogoje Staudingerjeve reakcije ter pripravili širok nabor poli(arilen iminofosforan)ov. Raziskali smo mehanizem oksidacije končnih fosfinskih skupin, kar je močno oviralo pretekle poskuse polimerizacije. Dušik, ki se sprošča tekom Staudingerjeve reakcije pa smo uporabili za pripravo samostoječih π-konjugiranih pen. Pripravljene konjugirane porozne polimere smo testirali za fotokatalitsko razgradnjo organskih onesnaževal v vodi, kot tudi za specifične fotosintetske aplikacije. Materiali so pokazali obetavne rezultate pri razgradnji modelnih onesnaževal, t.j. bisfenol A in anilin v vodi ter visoko katalitsko aktivnost za fotosulfoksidacijo tioanisola.

• Keywords: -