A metal-organic framework that exhibits CO 2 -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 CO ₂ -responsive magnetic MOF that converts from ferrimagnetic to paramagnetic on CO ₂ adsorption, and returns to the ferrimagnetic state on CO ₂ 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 CO ₂ 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 CO ₂ molecules accommodated in the framework.