New Architecture Based on Metal‐Organic Frameworks and Spin Crossover Complexes to Detect Volatile Organic Compounds

We present here the encapsulation of a spin crossover complex C 1 [Fe II (L)] (L: 4‐amino‐, 2‐(2‐pyridinylmethylene)hydrazide) inside MOF‐808(Zr), a chemically robust Metal‐Organic Framework. The compound C 1 ⊂MOF‐808 retains its crystallinity as well as a partial porosity compared to pristine MOF and shows solvatochromism under Volatile Organic compounds (VOCs) sorption associated to a spin state change of the guest complex. More specifically, this compound shows an interesting reversible color change under formaldehyde and formic acid vapor sorption and can therefore be considered as a new kind of optical VOCs chemosensor, opening new doors for developing a broad range of VOCs optical sensors.