Highly efficient synthesis of microporous zeolitic imidazolate framework-8 in dimethyl carbonate under ambient conditions

Abstract

In this work, we report the efficient synthesis of zeolitic imidazolate framework-8 (ZIF-8) under ambient conditions in only 1 h, using a slightly polar solvent, dimethyl carbonate (DMC), one of the recommended green solvents according to the CHEM21 solvent selection guide. The optimized reaction conditions allow ZIF-8 preparation with stoichiometric amounts of reagents (2-methylimidazole and Zn2+), minimizing the need for a large excess of organic linker, as is typically required in solvothermal methods with DMF, methanol, or water. These results demonstrate that ZIF-8 can be successfully prepared even in slightly polar media, in contrast to the previous literature. Yields ranging from 80 to 98% were obtained, and the influence of the solvent on the reaction was systematically discussed. The resulting ZIF-8 was fully characterized, revealing a microporous material with excellent textural properties and among the highest reported specific surface areas (up to 1708 m2 g−1) and pore volumes (up to 0.83 cc g−1), compared to state-of-the-art materials. In addition, DMC was efficiently recycled over three consecutive cycles, maintaining high yields and preserving the crystallinity of ZIF-8. The sustainability of the proposed method was thoroughly evaluated using both green metrics (E-factor and PMI) and Life Cycle Assessment (LCA), confirming a significant reduction in environmental impacts compared to the most commonly used organic solvent, for this purpose, dimethylformamide (DMF).