Preserving Macroporosity in Type III Porous Liquids.

Preserving large permanent pore structures in a fluid may endow conventional liquids with emergent physical properties. However, such materials are challenging to make because of the tendency of the pores to be filled and occupied by the solvent molecules. Here, we report the design and synthesis of the first Type III porous liquid (PL) containing uniform yet stable 480 nm cavities. This was achieved by first constructing a single crystalline hollow metal-organic framework (MOF), UiO-66-NH2 , through chemical etching. The thin yet defect-free MOF shell effectively excludes the bulky poly(dimethylsiloxane) solvent molecules from entering the cavity through its 4 Šaperture, resulting in the preservation of both micro- and macroporosity in the PL. These enormous void spaces allow the PL to reversibly host and release up to 27 wt % water for up to 10 cycles. The switching between the "dry" state and the "wet" state led to a large changes of the thermal conductivity of the PL from 0.140 to 0.256 W m-1 K-1 , affording a guest-responsive liquid thermal switch with a switching ratio of 1.8.

Directional Engraving within Single Crystalline Metal-Organic Framework Particles via Oxidative Linker Cleaving.

An oxidative linker cleaving (OLC) process was developed for surgical manipulation of the engraving process within single crystalline MOFs particles. The strategy relies on selective degradation of 2,5-dihydroxyterephthalic acid linker into small molecular fragments by oxidative ring-opening reactions, resulting in controllable scissoring of framework. By regulation of the generation and diffusion of oxidative species, the core MOFs will undergo divergent etching routes, producing a series of single crystalline hollow and yolk-shell MOF structures. In addition, the OLC process can be initiated and localized around the pre-embedded Pd NPs through on-site catalytic generation of oxidative species, leading to solitary confinement of multiple NPs within one single crystalline MOF particle, namely, a multi-yolk-shell structure. This unique architecture can effectively protect NPs from agglomeration while realizing size selective catalysis at the same time.