Water Sensitivity in Zn₄O-Based MOFs is Structure and History Dependent

Abstract

Moisture can cause irreversible structural collapse in metal-organic frameworks (MOFs) resulting in decreased internal surface areas and pore volumes. The details of such structural collapse with regard to pore size evolution during degradation are currently unknown due to a lack of suitable in situ probes of porosity. Here we acquire MOF porosity data under dynamic conditions by incorporating a flow-through system in tandem with positronium annihilation lifetime spectroscopy (PALS). From the decrease in porosity, we have observed an induction period for water degradation of some Zn4O-based MOFs that signals much greater stability than commonly believed to be possible. The sigmoidal trend in the degradation curve of unfunctionalized MOFs caused by water vapor has been established from the temporal component of pore size evolution as characterized by in situ PALS. IRMOF-3 is found to degrade at a lower relative humidity than MOF-5, a likely consequence of the amine groups in the structure, although, in contrast to MOF-5, residual porosity remains. The presence of an induction period, which itself depends on previous water exposure of the sample (history dependence), and sigmoidal temporal behavior of the moisture-induced degradation mechanism of MOFs was also verified using powder X-ray diffraction analysis and ex situ gas adsorption measurements. Our work provides insight into porosity evolution under application-relevant conditions as well as identifying chemical and structural characteristics influencing stability.

Exploitation of Guest Accessible Aliphatic Amine Functionality of a Metal–Organic Framework for Selective Detection of 2,4,6-Trinitrophenol (TNP) in Water

“…2). Interestingly, Ur-MOF presented excellent hydrolytic stability as anticipated, [107][108][109][110][111][112] owing to its hydrophobic naphthalene moities (Fig. 2), which further enthused us to comprehensively investigate its selective traceamount TNP-sensing performance in water.…”

Cadmium(II)–Triazole Framework as a Luminescent Probe for Ca2+ and Cyano Complexes

“…Notably, for related dynamic conversions between other MOFs, the product cannot be definitely characterized by the available methods; thus they are not referred to herein. Recently, we obtained {[Cu(tatrz) 2 [14c] Taking inspiration from the aforementioned points, [35] herein we investigated the anion-exchange reaction of the 2D architecture of 2. After gently stirring crystals of 2 (0.5 mmol) in a 1:8:1 solution of CHCl 3 /C 2 H 5 OH/H 2 O containing NaBr·2 H 2 O, NaI·2 H 2 O, or NaOAc·3 H 2 O (5 mmol) for 6 h, the crystals retain their crystalline appearances, excluding dissolution or recrystallization processes.…”

“…[43b] When the additional amount 2 ]·solvent, shows high sensitivity and a quick response toward the presence of a trace amount of NB in solution or vapor state, which may be used for NB sensing applications.…”

“…[1][2][3] Because there are numerous organic and inorganic functional moieties incorporated into the porous materials, MOFs demonstrate remarkable properties for applications in many fields, such as luminescence, gas storage, sensing, magnetics, and catalysis. [4][5][6][7] Nowadays, porous metal-organic frameworks (PMOFs) with dynamic behavior have received considerable interest because these functional coordination frameworks can exhibit guest-induced structural changes of the host lattice.…”

Modeling adsorption properties of structurally deformed metal–organic frameworks using structure–property map

“…For example, the metal ions and the organic ligands comprising the MOF structures are connected via coordination bonds that can lead to structures that possess both thermal and chemical instabilities (4,5). As such, MOFs can readily undergo structural transformations under many circumstances, which include various thermal/vacuum treatments on activation, and exposure to air/moisture on handling, leading to irreversible damage (6)(7)(8)(9). Although detrimental in most cases, the structural deformation can also be exploited to create strong binding sites that can enhance gas adsorption for sensing/storage purposes (10,11).…”