CO2-induced single-crystal to single-crystal transformations of an interpenetrated flexible MOF explained by in situ crystallographic analysis and molecular modeling

• Published in: Chemical science (Cambridge) 2019, Vol.10 (43), p.10018-10024
• Main Authors: Hazra, Arpan, van Heerden, Dewald P, Sanyal, Somananda, Lama, Prem, Esterhuysen, Catharine, Barbour, Leonard J
• Format: Article
• Language: English
• Subjects: Adsorption; Carbon dioxide; Computer simulation; Crystallography; Crystals; Desorption; Gas pressure; Metal-organic frameworks; Phase transitions; Single crystals; Thermogravimetric analysis; X ray powder diffraction; X-ray diffraction
• ISSN: 2041-6520; 2041-6539
• DOI: 10.1039/c9sc04043a

A molecular-level investigation is reported on breathing behaviour of a metal–organic framework (1) in response to CO2 gas pressure. High-pressure gas adsorption shows a pronounced step corresponding to a gate-opening phase transformation from a closed (1cp) to a large-pore (1lp) form. A plateau is observed upon desorption corresponding to narrow-pore intermediate form 1np which does not occur during adsorption. These events are corroborated by pressure-gradient differential scanning calorimetry and in situ single-crystal X-ray diffraction analysis under controlled CO2 gas pressure. Complete crystallographic characterisation facilitated a rationalisation of each phase transformation in the series 1cp → 1lp → 1np → 1cp during adsorption and subsequent desorption. Metropolis grand-canonical Monte Carlo simulations and DFT-PBE-D3 interaction energy calculations strongly underpin this first detailed structural investigation of an intermediate phase encountered upon desorption.