Experimental Confirmation of a Predicted Porous Hydrogen‐Bonded Organic Framework

• Published in: Angewandte Chemie International Edition Vol. 62; no. 34; pp. e202303167 - n/a
• Main Authors: Shields, Caitlin E., Wang, Xue, Fellowes, Thomas, Clowes, Rob, Chen, Linjiang, Day, Graeme M., Slater, Anna G., Ward, John W., Little, Marc A., Cooper, Andrew I.
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 21.08.2023; John Wiley and Sons Inc
• Edition: International ed. in English
• Subjects: Crystal Engineering; Crystal lattices; Crystal structure; Crystal Structure Prediction; Crystals; Hydrogen; Hydrogen-Bonded Organic Frameworks; Lattice energy; Organic chemistry; Porous Materials; Quinoxaline; Quinoxalines; Structure-function relationships; Hydrogen-Bonded Organic Frameworks; Crystal Engineering; Porous Materials; Crystal Structure Prediction
• DOI: 10.1002/anie.202303167
• ISSN: 1433-7851; 1521-3773

Hydrogen‐bonded organic frameworks (HOFs) with low densities and high porosities are rare and challenging to design because most molecules have a strong energetic preference for close packing. Crystal structure prediction (CSP) can rank the crystal packings available to an organic molecule based on their relative lattice energies. This has become a powerful tool for the a priori design of porous molecular crystals. Previously, we combined CSP with structure‐property predictions to generate energy‐structure‐function (ESF) maps for a series of triptycene‐based molecules with quinoxaline groups. From these ESF maps, triptycene trisquinoxalinedione (TH5) was predicted to form a previously unknown low‐energy HOF (TH5‐A) with a remarkably low density of 0.374 g cm−3 and three‐dimensional (3D) pores. Here, we demonstrate the reliability of those ESF maps by discovering this TH5‐A polymorph experimentally. This material has a high accessible surface area of 3,284 m2 g−1, as measured by nitrogen adsorption, making it one of the most porous HOFs reported to date. A hydrogen‐bonded framework that was predicted previously to have 3D porosity and a remarkably low density of 0.37 g cm−3 has been discovered experimentally. The structure of this framework matches the original prediction precisely and it has an accessible surface area of 3,284 m2 g−1, as measured by nitrogen adsorption, making it one of the most porous hydrogen‐bonded frameworks synthesized to date.