Metal–Organic Framework Thin Films Composed of Free-Standing Acicular Nanorods Exhibiting Reversible Electrochromism

A uniform
and crack-free metal–organic framework (MOF) thin
film composed of free-standing acicular nanorods was grown on a transparent
conducting glass substrate. The MOF thin film exhibits electrochromic
switching between yellow and deep blue by means of a one-electron
redox reaction at its pyrene-based linkers. The rigid MOF stabilizes
the radical cations of the pyrene linkers at positive applied potential,
resulting in the reversible color change of the MOF film. The regular
and uniform channels of the MOF allow ions to migrate through the
entire film. The MOF thin film thus exhibits a remarkable color change
and rapid switching rate.