Guest-responsive thermal expansion in the Zr-porphyrin metal-organic framework PCN-222

We use powder x-ray diffraction under variable temperature to study the thermal expansion of the metal-organic framework (MOF) PCN-222. The thermal expansion increases drastically in magnitude following more aggressive heating, which is rationalized by enhanced flexibility upon guest removal. Moreover, the thermal response strongly depends on the temperature: the volumetric expansivity nearly quadruples and the expansion along c changes sign upon cooling. Our results highlight the large flexibility of MOFs and the role of guest species. (C) 2022 Author(s).

Automated summary

This study investigates the thermal expansion of the metal-organic framework (MOF) PCN-222 using powder X-ray diffraction under variable temperature. The results show that the thermal expansion increases significantly with more aggressive heating, attributed to enhanced flexibility after guest removal. Furthermore, the thermal response exhibits strong temperature dependence, with a nearly quadruple volumetric expansivity and a change in the expansion direction along c upon cooling. These findings highlight the high flexibility of MOFs and the significance of guest species.