A Comparison of Two Isoreticular Metal–Organic Frameworks with Cationic and Neutral Skeletons: Stability, Mechanism, and Catalytic Activity

Abstract

Although many ionic metal–organic frameworks (MOFs) have been reported, little is known about how the charge of the skeleton affects the properties of the MOF materials. Herein we report how the chemical stability of MOFs can be substantially improved through embedding electrostatic interactions in structure. A MOF with a cationic skeleton is impervious to extremely acidic, oxidative, reductive, and high ionic strength conditions, such as 12 m HCl (301 days), aqua regia (86 days), H2O2 (30 days), and seawater (30 days), which is unprecedented for MOFs. DFT calculations suggested that steric hinderance and the repulsive interaction of the cationic framework toward positively charged species in microenvironments protects the vulnerable bonds in the structure. Diverse functionalities can be bestowed by substituting the counterions of the charged framework with identically charged functional species, which broadens the horizon in the design of MOFs adaptable to a demanding environment with specific functionalities.

Harnessing Electrostatic Interactions for Enhanced Conductivity in Metal-Organic Frameworks

“…Zn-S@PFC-8 Fabrication and Characterization. PFC-8 (Ni(BTAB)Cl 2 ) is a MOF with a cationic backbone and isolated Clas counterions inside pores [30]. Single-crystal Xray diffraction analysis reveals that each Ni(II) ion is square-planar coordinated by four N atoms and axialoccupied by two bridging Clto form a Ni(II) metal chain.…”

“…Taking this cue, we speculate that the electrostatic interaction plays a vital role in this drastic improvement. Therefore, a neutral framework PFC-9 (Ni(H 2 DPB)) [30], possessing similar ligands, identical metal centers, and same topology with PFC-8, was prepared and followed with the same Zn-S 2loading procedure (denoted as Zn-S@PFC-9) for electrical conductivity investigation (Scheme 2 and Figure S9). Since single crystals were not available for PFC-9, the conductivity measurements were performed on pressed square shape pellets using a two-point probe setup.…”

“…Analysis. The single crystal of PFC-8 was synthesized according to the previous report [30] with minor modifications. In brief, NiCl 2 •6H 2 O (16 mg) and 1,4-Bis(4H-1,2,4triazol-4-yl) benzene (BTAB) (10 mg) in 2 mL of N,Ndimethylformamide (DMF) solution and 0.6 mL of water charged in a vial were ultrasonicated for a few minutes and followed with the addition of 0.43 mL triethylamine.…”

Hierarchical Porous Graphene–Iron Carbide Hybrid Derived From Functionalized Graphene-Based Metal–Organic Gel as Efficient Electrochemical Dopamine Sensor

“…Metal–organic frameworks (MOFs) consisting of organic linkers bridging metal or metal–oxo clusters entail profound benefits when they are used in a variety of applications, such as separations, gas storage, chemical sensing, and catalysis (He et al, 2019 ; Chen et al, 2020 ; Huang et al, 2020 ; Roztocki et al, 2020 ). Nevertheless, their stability under certain environmental conditions and poor conductivity constitute limiting factors and pose a necessity for new strategies in MOF synthesis and design (Yuan et al, 2018 ).…”

Multifunctional Gold Nanoparticles@Imidazolium-Based Cationic Covalent Triazine Frameworks for Efficient Tandem Reactions

“…) could be absorbed into ICTF via electrostatic interaction, [25][26][27][28] while the MNPs could be stabilized by the N and the in situ formed N-heterocyclic carbene (NHC) species. [29][30][31][32] Therefore, in this work, we prepared highly ultrafine gold nanoparticles (AuNPs) encapsulated in ICTF (Au@ICTF) via a double-solvent method (DSM), [33][34][35] followed by reduction with NaBH 4 .…”