MOF crystal growth: UV resonance Raman investigation of metal-ligand binding in solution and accelerated crystal growth methods.

Determining the mechanism of metal-organic framework (MOF) crystal growth is important for the development of more efficient and reliable synthetic methods. Resonance Raman spectroscopy has been used for the first time to detect interactions in solution between metal ions and bridging ligands as MOFs form. UV excitation (229 nm) produced strong resonance enhancement of 4,4'-bipyridine (bpy) vibrational bands and showed that soluble Co(2+)-bpy species formed in solution prior to the growth of MOF crystals from bpy and Co(NO3)2. The results of the Raman experiments informed the development of faster methods for synthesizing [Co2(bpy)3(NO3)4]n 2D bilayer and [Co(bpy)(NO3)2(H2O)2]n 1D chain MOFs.