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.