Filipe Vilela

Surface Area Control and Photocatalytic Activity of Conjugated Microporous Poly(benzothiadiazole) Networks

P-conjugated microporous polymers, such as organic semiconductors with additional porosity in the nanorange, are versatile materials. In addition to typical applications for high-surface-area materials, such as gas separation and storage, 3] conjugated polymer networks are also potential heterogeneous catalysts and can be used in optoelectronics and for energy applications. Given the importance of surface area and porosity, a simple methodology to influence these parameters is needed. In order to use conjugated polymer networks as catalysts and catalyst supports their chemical stability needs to be improved. Therefore we designed a stable, fully conjugated network by linking benzothiadiazole as a strong electron-withdrawing moiety through three Csp Csp bonds to benzene as a weak electrondonating component. The surface area of these novel conjugated microporous polymer networks could be adjusted by a simple synthetic protocol. Benzothiadiazole monomers have proven great stability towards oxidation in photovoltaic applications. The lowband-gap character, high absorption coefficient, and suitable energy levels of benzothiadiazole result in a very strong acceptor to be used in optoelectronic materials, such as lowband-gap polymers, 8] non-fullerene acceptors, or n-type field effect transistors. The combination of weak electron donors, such as a phenyl group with benzothiadiazole, may prevent a fast recombination of excitons and increase the yield of intersystem crossing to the triplet state of the polymer, thereby rendering it suitable for photosensitizing. Conjugated linear polymers with backbones based on the poly(phenylene ethynylene) structure or the polythiophene–porphyrin dyad repeat unit can generate singlet oxygen in water upon irradiation. Singlet oxygen is used for a number of applications, such as for treatment of waste water or in the synthesis of fine chemicals. An industrial process carried out on a scale of several tons a year is the photochemical oxidation of citronellol to rose oxide. Different dyes and transition metal complexes can generate singlet oxygen upon irradiation, and these sensitizers can be used in homogeneous solution or immobilized on a solid support. Working under heterogeneous conditions allows for easy separation of the sensitizer after reaction and reusability. Traditional systems suffer however from quenching of the produced singlet oxygen by the solid support, which reduces the quantum yield. Incorporation of a photosensitizing structure into a polymer backbone is particularly attractive, because no support to immobilize the sensitizer is needed when an insoluble photoactive polymer network is used. Therefore the ability of the conjugated microporous polymer (CMP) network to act as a singlet oxygen photosensitizer was evaluated by employing the oxidation of a-terpinene to ascaridole. The pore size and structure as well as specific surface area are beneficial in providing a high accessibility of exited solid polymer for solubilized oxygen, thus resulting in high efficiency for singlet oxygen generation in dependence of the pore architecture. A series of polymer networks based on benzothiadiazole as building block was synthesized through palladium-catalyzed Sonogashira–Hagihara cross-coupling polycondensation of 4,7-dibromobenzo[c][1,2,5]thiadiazole with 1,3,5-triethynylbenzen (Scheme 1).

Modification of conjugated microporous poly-benzothiadiazole for photosensitized singlet oxygen generation in water

Water-dispersible alkyne-bearing conjugated microporous poly-benzothiadiazoles were synthesized using thiol-yne chemistry to enhance water compatibility. The water compatible polymer networks were used as heterogeneous photocatalysts to generate singlet oxygen for the conversion of furoic acid to 5-hydroxy-2(5H)-furanone.

A Phosphotyrosine‐Imprinted Polymer Receptor for the Recognition of Tyrosine Phosphorylated Peptides

Hyperphosphorylation at tyrosine is commonly observed in tumor proteomes and, hence, specific phosphoproteins or phosphopeptides could serve as markers useful for cancer diagnostics and therapeutics. The analysis of such targets is, however, a challenging task, because of their commonly low abundance and the lack of robust and effective preconcentration techniques. As a robust alternative to the commonly used immunoaffinity techniques that rely on phosphotyrosine(pTyr)-specific antibodies, we have developed an epitope-imprinting strategy that leads to a synthetic pTyr-selective imprinted polymer receptor. The binding site incorporates two monourea ligands placed by preorganization around a pTyr dianion template. The tight binding site displayed good binding affinities for the pTyr template, in the range of that observed for corresponding antibodies, and a clear preference for pTyr over phosphoserine (pSer). In further analogy to the antibodies, the imprinted polymer was capable of capturing short tyrosine phosphorylated peptides in the presence of an excess of their non-phosphorylated counterparts or peptides phosphorylated at serine.

Conjugated Microporous Networks on the Basis of 2,3,5,6‐Tetraarylated Diketopyrrolo[3,4‐c]pyrrole

π-Conjugated microporous networks have been prepared from the tetraarylated diketopyrrolo[3,4-c]pyrrole unit as a tetrafunctional building block. The reactions are carried out using microwave-assisted Yamamoto or Sonogashira cross-coupling. Red insoluble powders are obtained, showing intense fluorescence. The polymer networks exhibit a high gas storage capability, with BET surface areas up to about 500 m2 · g−1.

BODIPY-based conjugated polymers for broadband light sensing and harvesting applications

The synthesis of novel low band-gap polymers has significantly improved light sensing and harvesting in polymer–fullerene devices. Here the synthesis of two low band-gap polymers based on the 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene core (BODIPY), and either bis(3,4-ethylenedioxythiophene) (bis-EDOT) or its all-sulfur analogue bis(3,4-ethylenedithiathiophene) (bis-EDTT) are described. The polymers demonstrate ambipolar charge transport and are shown to be suitable for broadband light sensing and solar energy harvesting in solution-processable polymer–fullerene devices.

π-Conjugated polyHIPEs as highly efficient and reusable heterogeneous photosensitizers

π-Conjugated microporous polyHIPEs are synthesized via Suzuki cross-coupling. The polymeric backbone consists of electron donor and acceptor moieties with suitable energetic characteristics to promote the efficient photosensitizing ability for the activation of singlet oxygen, showing extraordinarily high stability. The reaction can be carried out in a continuous flow reaction set-up, realizing complete conversion of α-terpinene into ascaridole.

Phosphatase/temperature responsive poly(2-isopropyl-2-oxazoline)

We demonstrate a strategy for producing polymer bioconjugates which display both enzymatic and thermal responsiveness. This is achieved by combining the thermo-responsive properties of poly(2-isopropyl-2-oxazoline) (PiPrOx) with the self-assembly properties of fluorenylmethoxycarbonyl-tyrosine (Fmoc-Y), controlled by a phosphatase triggered mechanism.

Conjugated porous polymers for photocatalytic applications

Conjugated porous polymers (CPPs) are a class of fully crosslinked polymers defined by high surface area and porosity in the nanometer range, having been traditionally developed for applications such as gas storage, sensing and (photo)catalysis. As these materials are comprised of extended π-conjugation, their ability to act as light harvesters, and in turn photocatalysts, has come to prominence. The insoluble nature of CPPs allows them to be employed as photocatalysts under heterogeneous conditions, replacing traditional homogeneous systems. This Perspective highlights the current state-of-the-art CPPs along with a view to their applications as heterogeneous photocatalysts for a wide range of chemical transformations including hydrogen production, organic synthesis and photopolymerization, just to name but a few.

Well‐Defined and Monodisperse Linear and Star‐Shaped Quaterfluorene‐DPP Molecules: the Significance of Conjugation and Dimensionality

The synthesis of three new 1,4-diketo-3,6-diphenyl-pyrrolo[3,4-c]pyrrole (DPP) macromolecules appended with two or four quaterfluorene arms is reported. The compounds absorb mainly through the oligofluorene units and emit through the DPP core. Optical gain has been observed for Linear-c, a two-armed structure in which the quaterfluorene units are conjugated through the core unit.

Facile synthesis of a conjugated microporous polymeric monolith via copper-free Sonogashira–Hagihara cross-coupling in water under aerobic conditions

A conjugated microporous polymer was synthesized via a modified Sonogashira–Hagihara cross-coupling reaction under aerobic conditions in water and in the absence of copper. These conditions allowed the directing of the CMP format during synthesis into a monolithic structure. Post-modification of the polymer with thiol–yne chemistry followed by AgI uptake led to a catalytically active material for a heterocyclization reaction.