Fascinating chemistry or frustrating unpredictability: Observations in crystal engineering of metal-organic frameworks

Reticular design is a highly attractive concept, but coordination chemistry around the tectonic units of metal-organic frameworks (MOFs) and additional interplay with anionic and solvent species provide for dazzling complexity that effectively rules out structure prediction. We can however study the chemistry around pre-existing clusters, and assemble novel materials correspondingly, using a priori information about the connectivity of an investigated metal cluster. Studies, often spectroscopic of nature, have in recent years solved many puzzles in MOF crystallization. The obtained knowledge opens new doors in crystal engineering, but more research on MOF coordination chemistry has to be carried out.