Enhancing the stability of metal–organic framework via ligand modification: scalable synthesis and high selectivity of CO2 sorption property

Abstract

We show, herein, how the minor ligand modification led to the significant enhancement of both chemical and physical stabilities, as well as the gas sorption property of a Cu(II)-organic framework. Using two analogical bifunctional ligands, two new MOFs, namely {[Cu₄Cl(cpt)₄]·(NO₃)₃·4DMF·3H₂O}_n (1) and {[Cu₄(OH)₂(tpa)₄](NO₃)₂·2DMA·2H₂O}_n (2), with similar pore shapes but quite different stabilities were successfully synthesized and fully characterized by performing single crystal X-ray diffraction, powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA) and Fourier transform infrared (FT-IR) spectroscopy. Although both MOFs show similar pore shapes and topical structures, they have quite different stabilities and gas uptake properties. MOF 1 with a single-walled framework is insufficiently robust after the removal of the solvents, while MOF 2 with a double-walled framework could maintain its framework integrality after the activation. Moreover, MOF 2 exhibits excellent moisture-resist properties and can be easily scaled up with good crystal quality and high phase purity. In addition, the CO₂ sorption performances of activated MOF 2 were probed both experimentally and computationally.