Polarity-dependent particle size of zeolitic imidazolate framework synthesized in various solvents

ZIF-8 nano particles were synthesized in various solvents (water, alcohols and dimethylformamide) at 25 degrees C and effect of solvating solvent on particle morphology was studied. Solvating solvent strongly affected morphology of synthesized ZIF-8 particles. 2C and 3C alcohols derived agglomerates, while water and methanol, relatively isolated particles. The average size of ZIF-8 agglomerates decreased from 750 to 100 nm as dielectric constant of solvent increased (2-BtOH < 1-BtOH < 2-PrOH < 1-PrOH < EtOH < MeOH < water). The decrease in secondary particle size was explained by increased activation energy for agglomeration in the sequence. Primary crystallite size increased from 13 to 25 nm as hydrogen bond acceptance (HBA) value of solvents increased (2-BtOH < 2-PrOH < 1-BtOH < 1-PrOH < EtOH < MeOH < water). The increment in crystallite size was explained by enhanced deprotonation of Hmim in alcoholic system and Zn(Hmim)(n)(2+) in aqueous system. ZIF-8 particles showed CO2 adsorption of 243-266 mg g(-1) at 10 bar and considerable adsorption selectivity (CO2/N-2 = 7.9, CO2/H-2 = 6.7 and CO2/CH4 = 2.9). It could be concluded that selection of solvating solvent was one of important parameters to control morphology of ZIF-8 particles.

Automated summary

ZIF-8 nanoparticles were synthesized in various solvents at 25°C, showing that the solvating solvent strongly affected particle morphology. Different alcohols led to agglomerates, while water and methanol produced isolated particles. The size of ZIF-8 agglomerates decreased with increasing dielectric constant of the solvent.