Exceptional thermal stability in a supramolecular organic framework: porosity and gas storage

Yang, W. et al. (2010) Exceptional thermal stability in a supramolecular organic framework: porosity and gas storage. Journal of the American Chemical Society, 132(41), pp. 14457-14469. (doi: 10.1021/ja1042935) (PMID:20866087)

Abstract

Reaction of β-amino-β-(pyrid-4-yl)acrylonitrile with the aromatic dicarboxaldehydes 9,10-bis(4-formylphenyl)anthracene and terephthalaldehyde affords the dihydropyridyl products 9,10-bis(4-((3,5-dicyano-2,6-dipyridyl)dihydropyridyl)phenyl)anthracene (L1) and 1,4-bis(4-(3,5-dicyano-2,6-dipyridyl)dihydropyridyl)benzene (L2), respectively. In the solid state [L1]·2.5DMF·3MeOH (SOF-1) crystallizes in the monoclinic space group P21/c and forms a 3D stable supramolecular organic framework via strong N−H···Npy hydrogen bonds and π−π interactions. The material incorporates pyridyl-decorated channels and shows permanent porosity in the solid state. The pore volumes of the desolvated framework SOF-1a calculated from the N2 isotherm at 125 K and the CO2 isotherm at 195 K are 0.227 and 0.244 cm3 g−1, respectively. The N2 absorption capacity of SOF-1a at 77 K is very low, with an uptake of 0.63 mmol g−1 at 1 bar, although saturation N2 adsorption at 125 K is 6.55 mmol g−1 (or 143 cm3 g−1). At ambient temperature, SOF-1a shows significant CO2 adsorption with approximately 3 mol of CO2 absorbed per mole of host at 16 bar and 298 K, corresponding to 69 cm3 g−1 at STP. SOF-1a also adsorbs significant amounts of C2H2, with an uptake of 124 cm3 (STP) g−1 (5.52 mmol g−1) at 1 bar at 195 K. Methane uptake at 195 K and 1 bar is 69 cm3 (STP) g−1. Overall, gas adsorption measurements on desolvated framework SOF-1a reveal not only high capacity uptakes for C2H2 and CO2, compared to other crystalline molecular organic solids, but also an adsorption selectivity in the order C2H2 > CO2 > CH4 > N2. Overall, C2H2(270 K)/CH4(273 K) selectivity is 33.7 based on Henry’s Law constant, while the C2H2(270 K)/CO2(273 K) ratio of uptake at 1 bar is 2.05. The less bulky analogue L2 crystallizes in the triclinic space group P1̅ as two different solvates [L2]·2DMF·5C6H6 (S2A) and [L2]·2DMF·4MeOH (S2B) as pale yellow tablets and blocks, respectively. Each L2 molecule in S2A participates in two N−H···O hydrogen bonds between dihydropyridyl rings and solvent DMF molecules. Packing of these layers generates 1D nanochannels along the crystallographic a and b axes which host DMF and benzene molecules. In S2B, each L2 ligand participates in hydrogen bonding via an N−H···O interaction between the N−H of the dihydropyridyl ring and the O of a MeOH and also via an N···H−O interaction between the N center of a pyridine ring and the H−O of a second MeOH molecule. The presence of the L2−HOMe hydrogen bonds prevents ligand−ligand hydrogen bonding. As a result, S2B crystallizes as one-dimensional chains rather than as an extended 3D network. Thermal removal of solvents from S2A results in conversion to denser phase S2C which shows no effective permanent porosity.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Wilson, Dr Claire
• Authors: Yang, W., Greenaway, A., Lin, X., Matsuda, R., Blake, A. J., Wilson, C., Lewis, W., Hubberstey, P., Kitagawa, S., Champness, N. R., and Schröder, M.
• College/School: College of Science and Engineering > School of Chemistry
• Journal Name: Journal of the American Chemical Society
• Publisher: American Chemical Society
• ISSN: 0002-7863
• ISSN (Online): 1520-5126
• Published Online: 24 September 2010