Roeser,* J.; Dragica, P.; Bojdys, M. J.; Fayon, P.; Trewin, A.; Fitch, A. N.; Schmidt, M. U.; Thomas,* A. Nature Chemistry 2017. 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.
Glöcklhofer, F.; Petritz, A.; Karner, E.; Bojdys, M. J.; Stadlober, B.; Fröhlich, J.; Unterlass, M. M. Journal of Materials Chemistry C 2017. 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.
Want to find out more about the new “Charles University Center of Advanced Materials” (CUCAM)? Come along on the 8th of February to our kick-off workshop at Charles University, Department of Chemistry, Hlavova 8 in Prague!
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.
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
Cooper, A. I. and Bojdys, M. J. (2016). Two-dimensional carbon nitride material and method of preparation. WO2016027042 (A1).
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
“Michael J. Bojdys, head of the Functional Nanomaterials group at the Charles University in Prague, describes a class of [graphene-]analogous, two-dimensional sheets made from a mix of carbon and nitrogen that are here to complement the one property that the wonder material graphene has not: a useful electronic band gap.” – Dr Mara Staffilani
MaterialsViews 2016. [Link]
Highlight for the article: Bojdys,* M. J. Macromolecular Chemistry and Physics 2016, 217, 232–241. [DOI: 10.1002/macp.201500312]
Materials chemist Dr. Michael J. Bojdys received the junior grant of Czech Science Foundation (GA ČR) to promote the project “Crystalline fully-aromatic materials (CAMs)” over the next three years. The proposed materials will be tried and tested in applications such as heterogeneous catalysis, Li-ion batteries and gas sensors, as well as other industrially relevant applications.
Baumgartner, B.; Bojdys, M. J.; Skrinjar, P.; Unterlass,* M. M. Macromolecular Chemistry and Physics 2015, DOI: 10.1002/macp.201500287.
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.
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].
Bojdys,* M. J. Macromolecular Chemistry and Physics 2015, DOI: 10.1002/macp.201500312.
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.
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].