A metal-organic framework that exhibits CO₂-induced transitions between paramagnetism and ferrimagnetism

With adequate building blocks, metal-organic frameworks (MOFs) can combine magnetic ordering and porosity. This makes MOFs a promising platform for the development of stimuli-responsive materials that show drastically different magnetic properties depending on the presence or absence of guest molecules within their pores. Here we report a CO₂-responsive magnetic MOF that converts from ferrimagnetic to paramagnetic on CO₂ adsorption, and returns to the ferrimagnetic state on CO₂ desorption. The ferrimagnetic material is a layered MOF with a [D⁺-A^--D] formula, produced from the reaction of trifluorobenzoate-bridged paddlewheel-type diruthenium(II) clusters as the electron donor (D) with diethoxytetracyanoquinodimethane as the electron acceptor (A). On CO₂ uptake, it undergoes an in-plane electron transfer and a structural transition to adopt a [D-A-D] paramagnetic form. This magnetic phase change, and the accompanying modifications to the electronic conductivity and permittivity of the MOF, are electronically stabilized by the guest CO₂ molecules accommodated in the framework.