Controlling Zeolitic Imidazolate Framework Nano- and Microcrystal Formation: Insight into Crystal Growth by Time-Resolved In Situ Static Light Scattering

Abstract

We report on a simple and straightforward method that enables the rapid room-temperature production of nanocrystals (finely tuned in size between ∼10 and 65 nm) and microcrystals (∼1 μm) of the prototypical microporous zeolitic imidazolate framework (ZIF) material ZIF-8. Control of crystal size is achieved in a novel approach by employing an excess of the bridging bidentate ligand and various simple auxiliary monodentate ligands with different chemical functionalities (carboxylate, N-heterocycle, alkylamine). The function of the monodentate ligands can be understood as a modulation of complex formation and deprotonation equilibria during crystal nucleation and growth. Using time-resolved static light scattering, the functioning of modulating ligands is monitored for the first time by in situ experiments, which offered significant insight into the crystal growth processes. Formation of nanocrystals is characterized by continuous, comparatively slow nucleation and fast crystal growth occurring on a time scale of seconds. Although nucleation and growth are not separated from each other, a significant narrowing of the particle size distribution during early stages results in rather monodisperse nanocrystals, before broadening of the particle size distribution occurs, as observed by complementary ex situ electron microscopy studies. Microcrystal growth is dominated by a particleÀmonomer addition mechanism, but indications for the operation of a coalescence process during early stages of growth have been also obtained. During later stages of microcrystal growth crystals change their shape from cubes to rhombic dodecahedra. The prepared phase-pure ZIF-8 nanoscale materials exhibit good thermal stability in air and large surface areas, which are comparable to those of large macrocrystals. Nanocrystal powders exhibit dual micro-and mesoporosity.

Rapid room-temperature synthesis of hierarchical porous zeolitic imidazolate frameworks with high space-time yield

“…Notably, the shortest synthesis time in our strategy was only 1 min at RTP, whereas conventional solvothermal methods require a synthesis time of 24 h at HTP [18], demonstrating that organic amines play a significant role in accelerating the formation of ZIF-8. Gross et al [23], Nordin et al [24], and Cravillon et al [25] also reported that ZIFs could be synthesized within 10 min at RTP by using an organic amine (triethylamine) as a protonation agent, indicating that the organic amine (e.g., diethanolamine) used in this work acts as a protonation agent. However, the ZIFs synthesized with triethylamine as a protonation agent only possessed microporous structures instead of hierarchical porous structures.…”

“…The particle size of ZIF-8_A1 is considerably smaller than that of a previous ZIF-8 sample synthesized with triethylamine within 10 min (~100 nm) or C-ZIF-8 ( Fig. S1), [18,23] which can be attributed to fast nucleation (< 1 min) between deprotonated ligands and metal ions, resulting in the formation of small nanocrystals [23,25]. Furthermore, the apparent voids surrounded by the walls consisting of nanoparticles ( Fig.…”

“…S4), which can be attributed to the different protonation abilities of the organic amines. The protonation ability may affect the nucleation rate of the ZIFs, resulting in the formation of various crystal morphologies [25,36]. As shown in Fig.…”

Oriented Zeolitic Imidazolate Framework-8 Membrane with Sharp H2/C3H8 Molecular Sieve Separation

“…Parallel work of Cravillon et al have observed that in room-temperature syntheses cube-shaped crystals ({100} crystal form) first develop in early stages and eventually transform into rhombic dodecahedra ({110} crystal form). 44 The polyhedron (crystallographic point group symmetry 43m) consists of 12 rhombic faces perpendicular to AE110ae. When viewed along the AE100ae direction, one out of six corners is seen that lay on a 4-fold rotation axis (Figure 7b, upper left).…”

Lateral association and elongation of vimentin intermediate filament proteins: A time-resolved light-scattering study

“…Compared with singleangle setups, where assumptions about the morphology and size distribution of the particles are necessary to extract structural parameters, multiangle light scattering permits reliable extraction of the molecular weight (M w ), radius of gyration (R g ), and hydrodynamic radius (R H ) without specific assumptions about the shape and the degree of polydispersity of the particles, as previously demonstrated for the aggregation of dyestuff molecules and for nucleation and growth of silica particles (27,28). Application of this in situ technique provides us with a consistent set of M w , R g , and R H of assembling filaments and enables us to follow quantitatively and in real time the longitudinal growth of ULFs toward filaments of lengths up to 600 nm.…”