O'HARE GROUP

Carbon dioxide capture

New family of class 1 adsorbents for DAC by loading 67 wt% branched poly(ethylenimine) (PEI) onto Mg–Al–CO3 layered double hydroxide-derived mixed metal oxides (MMOs), which exhibit unexpectedly large CO2 uptakes (2.27 mmol g−1), fast kinetics (1.1 mmol g−1 h−1), and high stability over 20 cycles at 25 °C under 0.4 mbar CO2

 

The basicity and acidity of solvent-treated layered double hydroxide (ST-LDHs) and their layered double oxides (ST-LDOs) have been fully studied using Hammett titration, in situ FTIR, CO2-TPD and NH3-TPD. Five solvents (ethanol, acetone, isopropanol, ethyl acetate and 1-hexanol) were selected to treat [Mg0.72Al0.28(OH)2](CO3)0.14 (Mg2.5Al-CO3 LDH) and compared with traditional LDH co-precipitated from water. The Brønsted basicity strength of the ST-LDHs and ST-LDOs increased but was accompanied by a decrease in basic site density. In addition, the Lewis acidity of ST-LDOs also changes significantly, with medium strength Lewis acid sites dissapearing after solvent treatment. We found that the CO2 capture capacity of solvent treated LDOs is 50% higher than that of traditional co-precipitated LDO sample. The ethanol treated LDO exhibited the highest CO2uptake of 1.01 mmol g−1. The observed CO2 capture performance of the ST-LDOs correlates linearly with the ratio of total acid sites to total basic sites.

 
Recent publications:

Efficient CO2 capture from ambient air with Amine-functionalized Mg–Al mixed metal oxide nanosheets, X. Zhu, T. Ge, F. Yang, M. Lyu, C. Chen, D. O’Hare, R. Wang, J. Mater. Chem., A., (2020), 8, 16421-16428. 

Correlations of acidity-basicity of solvent treated layered double hydroxides/oxides and their CO2 capture performance, D.W.J. Leung, C. Chen, J.-C. Buffet and D. O'Hare, Dalton Trans., (2020), 49, 9306 - 9311. 

 

Carbon dioxide to methanol

Ultrathin (1–3 cationic-layers) (CuZn)1–xGax-CO3 layered double hydroxide (LDH) nanosheets were synthesized following the aqueous miscible organic solvent treatment (AMOST) method and applied as catalyst precursors for methanol production from CO2 hydrogenation. It is found that, upon reduction, the aqueous miscible organic solvent treated LDH (AMO-LDH) samples above a critical Ga3+ composition give consistently and significantly higher Cu surface areas and dispersions than the catalysts prepared from conventional hydroxyl-carbonate phases. Owing to the distinctive local steric and electrostatic stabilization of the ultrathin LDH structure, the newly formed active Cu(Zn) metal atoms can be stably embedded in the cationic layers, exerting an enhancement to the catalytic reaction. The best catalyst in this study displayed methanol productivity with a space-time yield of 0.6 gMeOH·gcat–1 h–1 under typical reaction conditions, which, as far as we are aware, is higher than most reported Cu-based catalysts in the literature.

 

CO2, a contributor to global warming, was converted into the valuable resource CH3OH by adding it to 2,2,6,6‐tetramethylpiperidine and B(C6F5)3 in toluene under H2 (1–2 atm), heating the mixture at 160 °C, and vacuum distillation. CH3OH was formed via the complex shown (C blue, N purple, O red, B orange, F green) as the sole C1 product.

 

Recent publications:

CO2hydrogenation to methanol over catalysts derived from single cationic layer CuZnGa LDH precursors, M. M.-J. Li, C. Chen, T. Ayvali, H. Suo, J. Zheng, I. F. Teixera, L. Ye, H. Zou, D. O’Hare and S. C. E. Tsang, ACS Catal., (2018), 8, 4390-4401. 

Non-metal Mediated Homogeneous Hydrogenation of CO2 to CH3OH, A.E. Ashley, A.L. Thompson and D. O’Hare, Angew Chemie Int Ed., (2009) 48, 9839 - 9843. 

 

Carbon dioxide activation

 

The novel 14 electron species η8-Pn*TiR2 (Pn* = C8Me6; R = Me, CH2Ph) have been synthesised and spectroscopically and structurally characterised. Subsequent reaction with CO2 leads to the activation and double insertion of CO2 into both Ti–alkyl bonds to form the electronically saturated η8-Pn*Ti(κ2-O2CR)2 (R = Me, CH2Ph) complexes.

 

Recent publications:

Double CO2 Activation by 14-electron η8-Permethylpentalene Titanium Dialkyl Complexes, R.T. Cooper, F.M. Chadwick, A.E. Ashley and D. O’Hare, Chemical Communications, (2015), 51, 11856 – 11859.