Shaping microcrystals of metal-organic frameworks by reaction-diffusion.

When components of a metal-organic framework (MOF) and a crystal growth modulator diffuse through a gel medium, they can form arrays of regularly-spaced precipitation bands containing MOF crystals of different morphologies. With time, slow variations in the local concentrations of the growth modulator cause the crystals to change their shapes, ultimately resulting in unusual concave microcrystallites not available via solution-based methods. The reaction-diffusion and periodic precipitation phenomena 1) extend to various types of MOFs and also MOPs (metal-organic polyhedra), and 2) can be multiplexed to realize within one gel multiple growth conditions, in effect leading to various crystalline phases or polycrystalline formations.