Nucleation of open framework materials: Navigating the voids

Research aimed at designing and optimizing open framework materials for commercial applications tend to focus on two critical objectives: identifying synthesis conditions that yield crystals with tailored physicochemical properties, and unlocking the untapped design space to achieve theoretical structures that far outnumber the list of synthetically realized materials. Accomplishing these goals requires detailed knowledge of nucleation in order to cultivate efficient, facile, and economical methods of controlling crystallization. The vast number of open framework materials that can be engineered through the judicious selection of inorganic or organic building units hold the promise for future discovery of materials with unique and superior properties compared to available porous materials. Herein, we review what is known about the nucleation of open framework crystals, highlighting the voids in our understanding of nucleation pathways, and we offer guidelines for advancing crystal engineering in this exciting area of research.