Thermal and Gas Dual-Responsive Behaviors of an Expanded UiO-66-Type Porous Coordination Polymer.

Through a modified solvothermal reaction using benzoic acid as an additive, the fcu-type framework [Zr6 O4 (OH)4 (edba)6 ] (H2 edba=4,4'-(ethyne-1,2-diyl)dibenzoic acid), an expanded version of UiO-66, is synthesized as high-quality single crystals, which can retain their single-crystallinity after solvent exchange and degas treatments. In situ variable-temperature single-crystal X-ray diffraction measurements show that the guest-free framework exhibits a remarkably large isotropic negative thermal expansion (α=-11.0×10-6  K-1 ) as a result of the transverse vibrational bending of the long organic ligand. By virtue of the relatively large π-conjugation system of the organic ligand, [Zr6 O4 (OH)4 (edba)6 ] also exhibits bright blue luminescence, which can be quenched efficiently by gaseous O2 (Ksv =2.4 bar-1 ).