Pressure-Induced Polymerization of Carbon Monoxide:  Disproportionation and Synthesis of an Energetic Lactonic Polymer

Abstract

We have studied pressure-induced chemical reactions in carbon monoxide using both a diamond-anvil cell and a modified large volume press. Our spectroscopic data reveal that carbon monoxide disproportionates into molecular CO 2 and a solid lactone-type polymer; photochemically above 3.2 GPa, thermochemically above 5 GPa at 300K, or at 3 GPa and ~2000K as achieved by laser heating. The solid product can be recovered at ambient conditions with a high degree of conversion, measured to be up to 95% of the original CO. Its fundamental chemical structure includes β-lactone and conjugated C=C, which can be considered a severely modified polymeric carbon suboxide with open ladders and smaller five-membered rings. The polymer is metastable at ambient conditions, spontaneously liberating CO 2 gases exothermically. We find that the recovered polymer has a high energy density, 1-8 KJ/g, and is very combustible. We estimate the density of recovered CO polymer to be at least 1.65 g/cm 3 .2

Controlling the Bonding and Band Gaps of Solid Carbon Monoxide with Pressure

“…Layered structures also appear in the polymerized solids of other molecules, such as N 2 [31] and CO 2 [26]. Structures with conjugated C ¼ C bonds as suggested by experiments [10,11] also appear in our search, but they are higher in energy than the chainlike polymers and purely single-bonded structures.…”

“…Pressure-induced polymerization of molecular crystals results in materials with entirely new electronic, optical, and physical properties [1,2]. CO is one of the most extensively studied molecular crystals [3][4][5][6][7][8][9][10][11][12]. Studies of polymerization of CO are motivated by the desire to understand the fundamental physics and chemistry of geological and planetary processes, where CO is present, and to search for new materials [13] exhibiting properties such as ''high energy density'' [10] and ''superhardness'' [14,15].…”

“…Molecular phases of CO and N 2 become unstable at high pressures because structures with single and double bonds are in general denser. Polymeric CO is also expected to be a good candidate high-energy-density material, as considerable energy is released on decomposition into C and CO 2 [10][11][12]. So far, only amorphous polymeric CO has been found in high pressure experiments.…”

“…Lipp et al [8] reported that the IR spectrum of the product is substantially different from that of poly-carbon suboxide and might be composed of -ðC ¼ OÞ-O-ðC-Þ¼C< units. Subsequent investigations have concluded that the polymer is based on lactone esters with rings closed by C ¼ C bonds [10,11]. Ceppatelli et al [12] investigated the effects of pressure and irradiation and showed that the reaction mechanisms are highly temperature dependent: the amorphous material produced at low temperature (< 300 K) is formed from polycarbonyl chains containing anhydride groups [R-ðC ¼ OÞ-O-ðC ¼ OÞ-R 0 ], while CO 2 and epoxy rings are formed at temperatures !…”

Pressure-induced structural and related electronic transitions in CaFe2O4and Fe2O3

“…Yamanaka et al [3] reported a martensitic structural phase transition in CaFe 2 O 4 at~50 GPa accompanied by a large volume drop. However, Merlini et al [4] based on single-crystal XRD claimed no change in symmetry, suggesting, based on the disappearance of the K â' satellite peak observed by XES, that the volume drop is a result of a high-spin (HS) to low-spin (LS) transition.…”