Synthesizing New Hybrid Zeolitic Imidazolate Frameworks by Controlled Demolition and Reconstruction

Abstract

A synthesis method to obtain new zeolite imidazolate framework (ZIF) materials that are otherwise difficult to synthesize by known techniques such as direct crystallization or solvent-assisted linker exchange, is demonstrated. Treatment of an easily synthesized “template” ZIF (such as ZIF-8) with an acid gas (humid SO2) allows controlled demolition of metal-linker coordination bonds, while preserving overall crystal topology. The partially demolished crystals are then reconstructed into highly crystalline mixed-linker ZIFs with unique characteristics by insertion of different linkers that displace the damaged linkers. One illustration shows the synthesis of a series of mixed-linker ZIFs containing benzimidazole linkers that show entirely different gate-opening and diffusion characteristics from ZIFs of the same composition prepared by direct crystallization. Also shown is the synthesis of new mixed-linker SOD-topology ZIFs containing bulky halobenzimidazole and alkylbenzimidazole linkers, which are very difficult to synthesize by other methods. The present method is seen to considerably reduce thermodynamic or kinetic barriers for replacement and insertion of linkers into ZIF topologies.

Synthesis of ZIF-8 Nanocrystals Mediated by CO2 Gas Bubbling: Dissolution and Recrystallization

“…However, when continuous CO 2 gas bubbling was introduced into the raw ZIF-8 slurry, the turbid slurry became gradually clear and transparent, indicating that the ZIF-8 phase was dissolved. This phenomenon is different from the partial demolition of Zn–N coordination bonds in ZIF-8 by acid gas treatment (humid SO 2 ), wherein ZIF-8 was only degraded to a slight degree (instead of total dissolution) . More interestingly, the solution turned milky again almost instantly after stopping the CO 2 gas bubbling, suggesting recrystallization and formation of ZIF-8-CO 2 .…”

“…This phenomenon is different from the partial demolition of Zn−N coordination bonds in ZIF-8 by acid gas treatment (humid SO 2 ), wherein ZIF-8 was only degraded to a slight degree (instead of total dissolution). 32 More interestingly, the solution turned milky again almost instantly after stopping the CO 2 gas bubbling, suggesting recrystallization and formation of ZIF-8-CO 2 . To the best of our knowledge, the interesting phenomenon has never been reported and experimentally observed.…”

Controlled Demolition and Reconstruction of Imidazolate and Carboxylate Metal–Organic Frameworks by Acid Gas Exposure and Linker Treatment

“…Our results suggest that SACRed is a versatile technique for introducing new linkers into MOFs after deliberate degradation by acid gases, resulting in highly crystalline materials. In each example, the fresh linkers introduced were of the same type as the original MOF, but we note that our recent work provides initial examples of using SACRed to produce mixed-linker ZIFs based upon a ZIF-8 template . The present work thus leads to the potential for producing a large range of new hybrid MOFs material by the controlled demolition and reconstruction methodology.…”

“…First, ZIF-8 “template” MOF materials were subjected to controlled demolition by different levels of humid SO 2 exposure. Then, the partially demolished ZIF-8 materials were treated with a solution of non-native linkers to reconstruct the materials in the form of mixed-linker ZIFs that retain the same crystal topology as ZIF-8 . With this approach, several bulky non-native linkers (benzimidazole, methylbenzimidazole, and halobenzimidazole) could be introduced into ZIF-8 while maintaining the sodalite (SOD) topology.…”

“…Then, the partially demolished ZIF-8 materials were treated with a solution of non-native linkers to reconstruct the materials in the form of mixed-linker ZIFs that retain the same crystal topology as ZIF-8. 17 With this approach, several bulky nonnative linkers (benzimidazole, methylbenzimidazole, and halobenzimidazole) could be introduced into ZIF-8 while maintaining the sodalite (SOD) topology. Such mixed-linker ZIFs containing linkers of disparate nature are difficult to obtain by techniques such as direct (de novo) mixed-linker synthesis 18 or solvent-assisted linker exchange (SALE).…”