Controlled synthesis of porous coordination-polymer microcrystals with definite morphologies and sizes under mild conditions.

Herein, we report a facile and convenient method for the synthesis of the porous coordination polymer MOF-14 [Cu3 (BTB)2 ] (H3 BTB=4,4',4''-benzene-1,3,5-triyl-tribenzoic acid) as microcrystals with definite shapes and crystal facets controlled by the reaction medium at room temperature. The amount of sodium acetate added to the reaction system plays a crucial role in the shape evolution of MOF-14 from rhombic dodecahedrons to truncated rhombic dodecahedrons and cubes with truncated edges and then to cubes. The addition of a base could accelerate the formation rate of crystal growth and increase the supersaturation of crystal growth, thus resulting in the formation of MOF-14 cube crystals with high-energy crystal facets. The morphological evolution was also observed for HKUST-1 [Cu3 (BTC)2 ] (H3 BTC=1,3,5-benzenetricarbocylic acid) from octahedrons to cubes, thus verifying the probable mechanism of the morphological transformation. The gas-adsorption properties of MOF-14 with different shapes were studied and reveal that the porous coordination-polymer microcrystals display excellent and morphology-dependent sorption properties.