Metal-Organic Framework Engineering: Directed Assembly from Molecules to Spherical Agglomerates

[In(OH)(bdc)]_n (bdc = 1,4-benzenedicarboxylate) was used as the model metal-organic framework for showing the concept of directed assembly from molecules to spherical agglomerates in solution. The course of reaction crystallization at 60^o, 80^o and 100^oC could be partially fulfilled by the Avrami equation. Noticeably, the portion which failed to be fitted by the equation was the secondary crystallization. Aging and editing effects during the course of secondary crystallization were responsible for the increase in crystallinity and structural rearrangements of [In(OH)(bdc)]_n crystals. The spherical agglomerates of [In(OH)(bdc)]_n crystals were assembled by the liquid bridges among the [In(OH)(bdc)]_n crystals through the addition of a polyethylene glycol (PEG) binder. The growth of spherical agglomerates was traced and described by three curves: the depletion curve, the reaction progress curve, and the average agglomerate size versus mixing time curve.