Redox-active porous materials for CO 2 capture and conversion Ulzhalgas Karatayeva and Prof. Charl F.J. Faul University of Bristol, UK Economic growth is closely linked to greenhouse gas (GHG) emissions, such as CO 2 , a fossil fuel combustion product. By 2022 its atmospheric concentration has reached 418 ppm, making it the most important contributor to global GHG emissions. 1 Therefore, research and technologies for its capture, storage and conversion are under development. Porous organic polymers (POPs) are promising materials in this area, in particular, conjugated microporous polymers (CMPs); they combine π-conjugated structures with a permanent porosity and thermal and chemical stability. 2 The polytriphenylamine (PTPA) network is an interesting CMP owing to its tunable properties, including conductivity. 3 These polymers are suitable for catalytic applications, resulting in materials that capture CO 2 and convert it into valuable products. Moreover, the introduction of heteroatoms and functional groups into the framework can increase the ability of these materials to adsorb and convert CO 2 . In particular, the carboxylic acid functional group shows promise owing to high binding capabilities with CO 2 molecules. 4 Here we report a novel class of carboxylic acid functionalised PTPA CMPs, synthesised by the palladium catalysed cross-coupling reaction of amines and aryl halides. The networks have been synthesised under different conditions, such as temperature, solvent and reactant feed ratios. Solvent choice has been directed by the Bristol-Xi’an Jiaotong (BXJ) approach 5,6 to tune surface area as well as pore size distributions (PSD). High levels of control can be achieved by calculating Hansen Solubility Parameters (HSPs) of the solvents and the formed polymers. Furthermore, the HSPs of the solvents were tuned using inorganic salts. Using these methods the carboxylic acid functionalised PTPA surface area was improved from 48 m 2 g -1 to 364 m 2 g -1 . In addition, CO 2 uptake was increased from 3 wt% to 7 wt%. Electrochemical reduction of CO 2 , using the networks as catalytic surfaces, is under investigation. Preliminary results show that carboxylic acid functionalised PTPA networks have promising electrocatalytic activity for the conversion of CO 2 to formate and methanol. Moreover, synthesised materials have excellent catalytic efficiency (90% conversion) for CO 2 fixation on epoxide (epichlorohydrin) to yield cyclic carbonates ((chloromethyl)ethylene carbonate) without any additives under mild reaction conditions. References 1. Global Climate Change: Vital Signs of the Planet, https://climate.nasa.gov/vital-signs/carbon-dioxide/, (accessed March 2022). 2. Y. Xu, S. Jin, H. Xu, A. Nagai, D. Jiang, Chem. Soc. Rev. 42 , 8012, 2013. 3. Y. Liao, J. Weber, C. F. J. Faul, Chem. Commun. 50 , 8002, 2014. 4. H. M. Lee, I. S. Youn, M. Saleh, J. W. Lee, K. S. Kim, Phys. Chem. Chem. Phys. 17 , 10925, 2015. 5. J. Chen, W. Yan, E. J. Townsend, J. Feng, L. Pan, V. Del Angel Hernandez, C. F. J. Faul, Angew. Chemie - Int. Ed. 58 , 11715, 2019. 6. J. Chen, T. Qiu, W. Yan, C. F. J. Faul, J. Mater. Chem. A 8 , 22657, 2020.
P36
© The Author(s), 2022
Made with FlippingBook Learn more on our blog