Water Based Synthesis of ZIF-8 Assisted by Hydrogen Bond Acceptors and Enhancement of CO2 Uptake by Solvent Assisted Ligand Exchange

Abstract

<jats:p>The aim of this work was to synthesize zeolitic imidazolate framework-8 (ZIF-8) by an alternative method and then modify the surface properties for enhancing the CO2 adsorption performance. The ZIF-8 was synthesized by a water based synthesis method using 2-methyl imidazole (2-MeIM) as a hydrogen bond donor and quaternary ammonium salts (QAS) as a hydrogen bond acceptor. The optimal synthesis conditions were investigated by varying (i) the order of precursor mixing during the synthesis process (ii) different QAS (tetrabutyl ammonium bromide (TBAB), tetraethyl ammonium bromide (TEAB) and trimethyl phenyl ammonium bromide (TMPAB)) and (iii) the ratio between 2-MeIM and QAS. The results show that the optimal synthesis condition was using TMPAB as the hydrogen bond acceptor with the ratio between 2-MeIM and TMPAB of 8:2 and in the order of first mixing both hydrogen bond donor and acceptor before adding Zn(NO3)2⋅6H2O solution. TMPAB can provide uniform size distribution with the smallest particle sizes of ZIF-8. This can be explained by the higher hydrogen bond strength between hydrogen bond donor (2-MeIM) and hydrogen bond acceptor (TMPAB) when compared with that of the rest of two QAS. The synthesized ZIF-8 was modified by solvent-assisted ligand exchange methods. The organic linker of ZIF-8 (2-MeIM) was exchanged by 2-aminobenzimidazole (2-NH2bZIM) and 2-phenylimidazole (2-PhIM). The CO2 uptake of modified ZIF-8 was enhanced upon exchanging with 2-NH2bZIM. The increase in CO2 uptake was due to an additional interaction between CO2 and exchanged imidazole linker and an increase in surface properties (higher surface area, pore size and pore volume).</jats:p>

Post-synthetic modification mechanism for 1D spin crossover coordination polymers

“…PSM methodologies are known to be solvent dependent. Solvent-assisted ligand exchange (SALE) 49–57 is a very interesting example on how a solid that, once formed, is considered inert can be modified in the presence of a solvent. This occurs as a single crystal to single crystal transformation in a heterogeneous manner by incorporating a new linker into the parent material.…”

Hierarchical Amine-Functionalized ZIF-8 Mixed-Matrix Membranes with an Engineered Interface and Transport Pathway for Efficient Gas Separation

“…Figure b shows the characteristic proton peaks of the two ortho-phenyl moieties (assigned “a” and “b”) in 2-aminobezimidazole observed at δ = 7.26 and 7.39 ppm. In addition, the characteristic proton peaks of the methyl group (assigned “d”) and imidazole (assigned as “c”) in 2-methylimidazole were observed at δ = 7.31 and 2.64 ppm in Figure b. − The ratio of the mixed organic ligands in the hierarchical ZIF-8-NH 2 nanoparticles was estimated by integrating the characteristic peaks and the following equation: The actual molar ratio of the mixed organic ligands was 95 mol % 2-methylimidazole and 5 mol % 2-aminobenzimidazole. The FT-IR and 1 H NMR spectra indicate that the hierarchical ZIF-8-NH 2 nanoparticles include the mixed organic ligands, i.e., both 2-methylimidazole and 2-aminobenzimidazole, in the framework.…”

“…The 6FDD characteristic peaks include C�O and C−N stretching bonds observed at 1719 and 1354 cm −1 , respectively. 53,54 Meanwhile, the intensity of the characteristic peaks of the 6FDD/ZIF-8-NH 2 MMMs increases upon increasing the loading of the hierarchical ZIF-8-NH 2 nanoparticles. For example, the intensity of peaks observed at 420 and 1146 cm −1 increase, which are assigned as the Zn−N bond from the metal−ligand coordination in the framework and the aromatic C−N bond in 2-methylimidazole.…”

“…The FT-IR spectra of 6FDD/ZIF-8-NH 2 MMM with a higher MOF weight loading exhibit 6FDD characteristic peaks with decreased intensity. The 6FDD characteristic peaks include C�O and C−N stretching bonds observed at 1719 and 1354 cm −1 , respectively 53,54. Meanwhile, the intensity of the characteristic peaks of the 6FDD/ZIF-8-NH 2 MMMs increases upon increasing the loading of the hierarchical ZIF-8-NH 2 nanoparticles.…”

Removal of carbon dioxide using zeolitic imidazolate frameworks: Adsorption and conversion via catalysis

“…SALE of ZIF‐8 was reported using linkers of 2‐mercaptobenzimidazole (SHBzIm), 2‐aminobenzimidazole (NH 2 BzIm), 2‐nitroimidazole (NO 2 Im), and 2‐phenylimidazole (PhIm). [ 193,198 ] CO 2 adsorption increases (from 42.7 to 48.2 cm 3 g −1 ) with the rise of the amine percentage from 5% to 16% via the SALE of ZIF‐8 (Figure 8). [ 193 ] Although SALE reduced the BET surface area of LeZIF8‐NH 2 BzIm (ligand exchange) derivatives, their CO 2 adsorption increased.…”