From Molecules to Carbon Materials—High Pressure Induced Polymerization and Bonding Mechanisms of Unsaturated Compounds

Abstract

With the development of high-pressure apparatus, in situ characterization methods and theoretical calculations, high-pressure technology becomes a more and more important method to synthesize new compounds with unusual structures and properties. By compressing compounds containing unsaturated carbon atoms, novel poly-ionic polymers, graphanes and carbon nanothreads were obtained. Their compositions and structures were carefully studied by combining multiple cutting-edge technologies, like the in situ high-pressure X-ray and neutron diffraction, transmission electron microscopy, pair distribution function, solid-state nuclear magnetic resonance and gas chromatography-mass spectroscopy. The reaction mechanisms were investigated based on the crystal structure at the reaction threshold pressure (the pressure just before the reaction taking place), the long-range and short-range structure of the product, molecular structure of the intermediates, as well as the theoretical calculation. In this review, we will summarize the synthesis of carbon materials by compressing the unsaturated compounds and its reaction characteristics under extreme conditions. The topochemical reaction mechanism and related characterization methods of the molecular system will be highlighted. This review will provide a reference for designing chemical reaction and exploring novel carbon materials under high-pressure condition.

Scalable High-Pressure Synthesis of sp2–sp3 Carbon Nanoribbon via [4 + 2] Polymerization of 1,3,5-Triethynylbenzene

“…Pressure-induced polymerization (PIP) of aromatics is a robust method to synthesize novel carbon materials. − By compression of benzene to ∼20 GPa at room temperature, ultrathin one-dimensional (1-D) sp 3 carbon nanothreads were obtained, with a stiff diamond-like structure . Introducing functional groups and heteroatoms can modify the reaction process, structure, and properties of the product; hence, a variety of aromatics were investigated, like furan, , pyrrole, thiophene, , pyridine, , aniline, pyrimidine, , triazine, ,, 2,4,6-tricyano-1,3,5-triazine (TCT), benzene–hexafluorobenzene cocrystal, and benzene–acetylene cocrystal .…”

Pressure-Induced Polymerization: Addition and Condensation Reactions

“…In practice, molecules always tend to polymerize upon compression, which is referred as pressure-induced polymerization (PIP). We have provided a schematic quantitative thermodynamic explanation and discussions on this in a very recent paper and in previous reviews [4][5][6][7][8][9]. The key point is, the contribution of external pressure to enthalpy is the integral of the equation of state of each material on the pressure-axis, and the difference between the integral of product and reactant is the contribution of external pressure to the enthalpy change of the reaction (Scheme 1, [4]).…”

“…Molecules 2021, 26, x FOR PEER REVIEW 2 of 22 paper and in previous reviews [4][5][6][7][8][9]. The key point is, the contribution of external pressure to enthalpy is the integral of the equation of state of each material on the pressure-axis, and the difference between the integral of product and reactant is the contribution of external pressure to the enthalpy change of the reaction (Scheme 1, [4]).…”

“…In this paper, we mainly review the recent works of our group on the PIP of molecules. There are already many excellent reports and reviews in this field and related areas [5][6][7][8][9][10][11][12][13], which we are not going to repeat here. Our group mainly focuses on the exploration of carbon-based materials using PIP, and has made great efforts on unrevealing the chemical reaction mechanism of PIP under HP.…”

A Short Review of Current Computational Concepts for High-Pressure Phase Transition Studies in Molecular Crystals

“…One can easily understand that many of the materials we use every day are exposed to relatively high pressures and sometimes high temperatures and, for sure, should be studied for possible undesirable phase transitions. Another application of high pressures is discovering new forms of different elements and substances, which may exhibit new valuable properties [17][18][19][20][21][22]. Stabilizing new forms obtained at high pressures at ambient conditions is an ambitious aim for applied science and industry-graphite transforming to diamonds is the most popular example of this possible process.…”