Photochemically Crushable and Regenerative Metal-Organic Framework.

A photochemically crushable and regenerative metal-organic framework (DTEMOF) was developed by complexation of photochromic ligand PyDTEopen and 5-nitroisophthalate (nip2-) with Cd2+ in DMF/MeOH. DTEMOF ([Cd(nip)(PyDTEopen)(H2O)(DMF)2]n) was obtained as colorless crystals. Its crystal structure revealed that DTEMOF adopts a tubular structure with interlocked coordination networks and can accommodate guest molecules in its one-dimensional pores. When DTEMOF suspended in DMF/MeOH was exposed to UV light, its crystalline network, though thermally stable up to 260 °C, was readily crushed to afford a homogeneous blue-colored solution, via ring-closing isomerization of the constituent PyDTEopen ligand into PyDTEclosed. Upon successive exposure of this solution to visible light, colorless MOF crystals identical to those of DTEMOF were regenerated. Light-responsive DTEMOF enabled highly efficient on-demand guest release.