Gas-responsive porous magnet distinguishes the electron spin of molecular oxygen

Gas-sensing materials are becoming increasingly important in our society, requiring high sensitivity to differentiate similar gases like N 2 and O 2 . For the design of such materials, the driving force of electronic host-guest interaction or host-framework changes during the sorption process has commonly been considered necessary; however, this work demonstrates the use of the magnetic characteristics intrinsic to the guest molecules for distinguishing between diamagnetic N 2 and CO 2 gases from paramagnetic O 2 gas. While the uptake of N 2 and CO 2 leads to an increase in T C through ferrimagnetic behavior, the uptake of O 2 results in an O 2 pressure-dependent continuous phase change from a ferrimagnet to an antiferromagnet, eventually leading to a novel ferrimagnet with aligned O 2 spins following application of a magnetic field. This chameleonic material, the first with switchable magnetism that can discriminate between similarly sized N 2 and O 2 gases, provides wide scope for new gas-responsive porous magnets.