Selective CO2 Trapping in Guest-Free Hydroquinone Clathrate Prepared by Gas-Phase Synthesis

Abstract

The most important process to make hydrogen is based on steam reforming of natural gas according to an overall reaction CH 4 + 2H 2 O!4H 2 + CO 2 , where after reformation of the natural gas to a CO/H 2 mixture (syngas) a water-gas shift reaction results in a predominantly CO 2 /H 2 mixture. [1,2] Steam reforming potentially offers one technological path to extend the trend of decarbonization of the primary fossil fuel by taking advantage of the low 1:4 carbon-to-hydrogen ratio of methane compared to coal (~8:4) and oil (~2:4), provided that subsequent separation of the CO 2 /H 2 mixture and sequestration of CO 2 is cost-effective and feasible. We present here a guest-free hydroquinone (HQ) clathrate, prepared by gas-phase synthesis, which reveals unique selectivities towards CO 2 /CH 4 and CO 2 /H 2 mixtures. A dynamical pore-widening process allows CO 2 to be adsorbed with a selectivity of 29:1 from a CO 2 /CH 4 (50:50 v/v) mixture and with a selectivity of 60:1 reversibly stored at 7 MPa and 298 K in the presence of a CO 2 /H 2 (50:50 v/v) mixture. This first example of a flexible hydrogen-bonded organic framework (HOF) that can reversibly and selectively absorb and store CO 2 opens up a host of applications.The

Fast and reversible hydrogen storage in channel cages of hydroquinone clathrate

“…Figure 1a shows the synchrotron XRD pattern of the guest-free HQ clathrate, which is prepared by the gas-phase synthesis of CO 2 -loaded HQ clathrate, and then followed by the controlled heating process. As shown in this figure, the guest-free HQ clathrate reveals a b-form HQ structure with the 1D channel cages, indicating that the controlled heating process leads to removal of CO 2 guests by maintaining the structural integrity of the original HQ host lattice [12]. However, the some unusual shape of XRD peaks may be attributed to stacking faults in the structure and/or lattice distortion by CO 2 removal during the controlled heating process.…”

“…At the first, the CO 2 -loaded HQ clathrate was synthesized by a solid-gas reaction between the a -form HQ (powdered HQ, $100 lm) and CO 2 gas at 20-80°C and 4 MPa for 30 h [12,13]. To remove CO 2 from the HQ clathrate framework, the CO 2 -loaded HQ clathrate was kept at 65°C and ambient pressure for 12 h under nitrogen environment.…”

“…However, the gas-phase synthesis of the guest-free HQ clathrate may provide an experimental means to address the broader challenge for industrial applications. Therefore, we presented previously a simple method to prepare the guest-free HQ clathrate without complicated chemical syntheses [12]. This involves the synthesis of the CO 2 -loaded HQ clathrate by a reaction between host HQ and guest CO 2 molecules, followed by removal of the CO 2 guests by controlled heating process to maintain the structural integrity of the original HQ host lattice.…”

Characterization Study of CO2, CH4, and CO2/CH4 Hydroquinone Clathrates Formed by Gas–Solid Reaction

“…The purpose of this study is therefore to provide an extended set of characteristics concerning HQ clathrates obtained by gas−solid reaction. The clathrates were characterized using a wide range of experimental methods: three spectroscopic techniquesRaman and Fourier transform IR (vibrational) and 13 C NMRwere used to obtain cross sectional data giving the key elements to easily identify the different structures and evaluate the reaction conversion from α to β HQ after the synthesis. Optical microscopy and scanning electron microscopy (SEM) analyses were performed to investigate the surface of the clathrates.…”

Hydroquinone clathrates by temperature-dependent terahertz time-domain spectroscopy

“…THz-TDS allows us to examine both intramolecular and intermolecular vibrations related to the hydrogen bonding networks and the interactions between molecules in the framework structure [1]. This suggests the potential of THz-TDS in studying the dynamics of the host-guest interaction of inclusion compounds composed of gaseous guest molecules and solid state host frameworks [2][3][4]. As shown Fig 1, THz-TDS is based on the optoelectronic generation and detection of a beam of subpicosecond THz pulses.…”