Category Archives: Publication

Functional carbon nitride materials — design strategies for electrochemical devices

Kessler, F. K.; Zheng, Y.; Schwarz, D.; Merschjann, C.; Schnick, W.; Wang, X.; Bojdys,* M. J. Nature Reviews Materials 2017, Article number: 17030 (2017), DOI: 10.1038/natrevmats.2017.30

In the past decade, research in the field of artificial photosynthesis has shifted from simple, inorganic semiconductors to more abundant, polymeric materials. For example, polymeric carbon nitrides have emerged as promising materials for metal-free semiconductors and metal-free photocatalysts. Polymeric carbon nitride (melon) and related carbon nitride materials are desirable alternatives to industrially used catalysts because they are easily synthesized from abundant and inexpensive starting materials. Furthermore, these materials are chemically benign because they do not contain heavy metal ions, thereby facilitating handling and disposal. In this Review, we discuss the building blocks of carbon nitride materials and examine how strategies in synthesis, templating and post-processing translate from the molecular level to macroscopic properties, such as optical and electronic bandgap. Applications of carbon nitride materials in bulk heterojunctions, laser-patterned memory devices and energy storage devices indicate that photocatalytic overall water splitting on an industrial scale may be realized in the near future and reveal a new avenue of ‘post-silicon electronics’.

DOI: 10.1038/natrevmats.2017.30

Anionic silicate organic frameworks constructed from hexacoordinated silicon centres

Roeser,* J.; Dragica, P.; Bojdys, M. J.; Fayon, P.; Trewin, A.; Fitch, A. N.; Schmidt, M. U.; Thomas,* A. Nature Chemistry 2017, Advance Article, DOI: 10.1038/NCHEM.2771

Crystalline frameworks composed of hexacoordinated silicon species have thus far only been observed in a few high pressure silicate phases. By implementing reversible Si–O chemistry for the crystallization of covalent organic frameworks, we demonstrate the simple one-pot synthesis of silicate organic frameworks based on octahedral dianionic SiO6 building units. Clear evidence of the hexacoordinated environment around the silicon atoms is given by 29Si nuclear magnetic resonance analysis. Characterization by high-resolution powder X-ray diffraction, density functional theory calculation and analysis of the pair-distribution function showed that those anionic frameworks—M2[Si(C16H10O4)1.5], where M = Li, Na, K and C16H10O4 is 9,10-dimethyl-2,3,6,7-tetraolatoanthracene—crystallize as two-dimensional hexagonal layers stabilized in a fully eclipsed stacking arrangement with pronounced disorder in the stacking direction. Permanent microporosity with a two-step filling process was evidenced by gas-sorption measurements. The negatively charged backbone balanced with extra-framework cations and the permanent microporosity are characteristics that are shared with zeolites.

DOI: 10.1038/NCHEM.2771

Dicyano- and tetracyanopentacene: foundation of an intriguing new class of easy-to-synthesize organic semiconductors

Glöcklhofer, F.; Petritz, A.; Karner, E.; Bojdys, M. J.; Stadlober, B.; Fröhlich, J.; Unterlass, M. M. Journal of Materials Chemistry C 2017, Advance Article, DOI: 10.1039/C7TC00143F.

Cyanated pentacenes are very promising candidate materials for ambipolar and n-type transistors. However, only a few examples have been obtained to date – all requiring lengthy, multi-step processes. Herein, we present the first preparation of 5,7,12,14-tetracyanopentacene (TCP) and a facile, scaled-up preparation of 6,13-dicyanopentacene (DCP). Both compounds are prepared by a one-pot synthesis using cheap quinones as starting materials. Detailed crystallographic investigations evince that the bulk assemblies of both cyanated pentacenes are dominated by non-covalent interactions, resulting in a dense, stable, face-to-face packing and in an intriguing packing motif for TCP. Very low frontier molecular orbital energy levels and a reversible bleaching of TCP are revealed by cyclic voltammetry. Finally, both cyanated pentacenes are used in proof-of-concept organic thin-film transistors (OTFTs) operating under ambient conditions. This work highlights the potential of cyanation for larger acenes and presents a straightforward route to the rational design of this promising class of materials.

DOI: 10.1039/C7TC00143F

Carbon nitride frameworks and dense crystalline polymorphs

Pickard, C. J.; Salamat, A.; Bojdys, M. J.; Needs, R. J.; McMillan, P. F. Physical Review B 2016, 94, 094104, DOI: 10.1103/PhysRevB.94.094104, arXiv:1605.02893.

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We used ab initio random structure searching (AIRSS) to investigate polymorphism in C3N4 carbon nitride as a function of pressure. Our calculations reveal new framework structures, including a particularly stable chiral polymorph of space group P43212 containing mixed sp2 and sp3-bonding, that we have produced experimentally and recovered to ambient conditions. As pressure is increased a sequence of structures with fully sp3-bonded C atoms and three-fold coordinated N atoms is predicted, culminating in a dense Pnma phase above 250 GPa. Beyond 650 GPa we find that C3N4 becomes unstable to decomposition into diamond and pyrite-structured CN2.

DOI: 10.1103/PhysRevB.94.094104, arXiv:1605.02893

WO2016027042 (A1) – Two-dimensional carbon nitride material and method of preparation

Cooper, A. I. and Bojdys, M. J. (2016). Two-dimensional carbon nitride material and method of preparation. WO2016027042 (A1).

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Graphitic carbon nitride has been prepared and its structure confirmed by extensive characterization. This material has useful electronic, in particular semiconducting, properties. Crystalline thin films have been prepared. Synthesis may be carried out by condensation of unsaturated carbon- and nitrogen- containing compound(s) in inert solvent such as a salt melt, forming graphitic carbon nitride at a gas-liquid or solid-liquid interface.

External Links: Patentscope, Espacenet, Google Patents

Design Strategies in Hydrothermal Polymerization of Polyimides

Baumgartner, B.; Bojdys, M. J.; Skrinjar, P.; Unterlass,* M. M. Macromolecular Chemistry and Physics 2015, DOI: 10.1002/macp.201500287.

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Hydrothermal polymerization, a benign synthesis for aromatic polyimides, is studied in detail to gain greater insight in the ongoing mechanisms. By performing an extensive set of experiments at various parameters, polyimides of outstanding crystallinity are obtained and could thus refine their crystal structure from powder XRD data. Initial condensation intermediates could isolate, which indicates that HTP is mechanistically closely related to classical step-growth polycondensations.

DOI: 10.1002/macp.201500287

This is the pre-peer reviewed version of the following article: Baumgartner, B.; Bojdys, M. J.; Skrinjar, P.; Unterlass,* M. M. Macromolecular Chemistry and Physics 2015, DOI: 10.1002/macp.201500287, which has been published in final form at [DOI: 10.1002/macp.201500287].

2D or not 2D-layered functional (C, N) materials “beyond silicon and graphene”

Bojdys,* M. J. Macromolecular Chemistry and Physics 2015, DOI: 10.1002/macp.201500312.

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As of 2015, the number of mobile phone subscriptions outstrips Earth’s human population. Critical raw materials (CRMs) and silicon, won in energy intensive refinement make up the electronics in all these devices. While graphene still has to deliver on its potential in electronic applications, we look to 2D polymer materials that go beyond silicon and graphene.

DOI: 10.1002/macp.201500312

This is the pre-peer reviewed version of the following article: Bojdys,* M. J. Macromolecular Chemistry and Physics 2015, DOI: 10.1002/macp.201500312, which has been published in final form at [DOI: 10.1002/macp.201500312].

Carbon nitride vs. graphene – now in 2D!

Cooper, A. I.; Bojdys,* M. J. Materials Today 2014, 17, 468–469.

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A polymer laboratory might not be your first port-of-call for replacement materials for silicon in sensors and transistors, but polymer chemistry and organic synthesis may have much to offer here: enter the world of modular chemical design of new 2-dimensional materials.

DOI: 10.1016/j.mattod.2014.10.001 [Download]

This article is published under the terms of the Creative Commons Attribution-NonCommercial-No Derivatives License (CC BY NC ND) in final form at [DOI: 10.1016/j.mattod.2014.10.001].

Frontispiece: Triazine-Based Graphitic Carbon Nitride: a Two-Dimensional Semiconductor

Algara-Siller, G.; Severin, N.; Chong, S. Y.; Björkman, T.; Palgrave, R. G.; Laybourn, A.; Antonietti, M.; Khimyak, Y. Z.; Krasheninnikov, A. V.; Rabe, J. P.; Kaiser, U.; Cooper,* A. I.; Thomas, A.; Bojdys,* M. J. Angewandte Chemie International Edition 2014, 53, 7450–7455.

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Graphitic Carbon Nitride

In their Communication on page 7450 ff., A. I. Cooper, M. J. Bojdys, et al. report crystalline thin films of triazine-based graphitic carbon nitride (TGCN). TGCN is structurally similar to graphite but it is a semiconductor, and the thin films display a direct bandgap between 1.6 and 2.0 eV.

DOI: 10.1002/anie.201482971

Triazine-Based, Graphitic Carbon Nitride: a Two-Dimensional Semiconductor

Algara-Siller, G.; Severin, N.; Chong, S. Y.; Björkman, T.; Palgrave, R. G.; Laybourn, A.; Antonietti, M.; Khimyak, Y. Z.; Krasheninnikov, A. V.; Rabe, J. P.; Kaiser, U.; Cooper,* A. I.; Thomas, A.; Bojdys,* M. J. Angewandte Chemie International Edition 2014, 53, 7450–7455.

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Graphitic carbon nitride has been predicted to be structurally analogous to carbon-only graphite, yet with an inherent bandgap. We have grown, for the first time, macroscopically large crystalline thin films of triazine-based, graphitic carbon nitride (TGCN) using an ionothermal, interfacial reaction starting with the abundant monomer dicyandiamide. The films consist of stacked, two-dimensional (2D) crystals between a few and several hundreds of atomic layers in thickness. Scanning force and transmission electron microscopy show long-range, in-plane order, while optical spectroscopy, X-ray photoelectron spectroscopy, and density functional theory calculations corroborate a direct bandgap between 1.6 and 2.0 eV. Thus TGCN is of interest for electronic devices, such as field-effect transistors and light-emitting diodes.

DOI: 10.1002/anie.201402191

This is the pre-peer reviewed version of the following article: Algara-Siller, G.; Severin, N.; Chong, S. Y.; Björkman, T.; Palgrave, R. G.; Laybourn, A.; Antonietti, M.; Khimyak, Y. Z.; Krasheninnikov, A. V.; Rabe, J. P.; Kaiser, U.; Cooper,* A. I.; Thomas, A.; Bojdys,* M. J. Angewandte Chemie International Edition 2014, 53, 7450–7455, which has been published in final form at [DOI: 10.1002/anie.201402191].