Solventless Synthesis of MOFs at High Pressure

Abstract

Besides the substitution or minimization of the use of harmful solvents, one essential goal of chemistry is to try to avoid their use altogether whenever possible. In the case of the synthesis of MOFs (metal–organic frameworks), this can only be achieved by finding alternatives to conventional processes. An example is the approach described here which involves working at high pressure (at 0.31 GPa) without using a solvent. This has evident advantages over mechanochemical synthesis by grinding or milling (also a solventless process) where the sample is submitted to attrition. The present paper reports the simple high pressure synthesis of the ZIF (zeolitic imizadolate framework) ZIF-8. This methodology enables fast synthesis of MOF materials and offers new insights into their industrial implementation. In addition, this technique could be applied to the synthesis of other MOFs and even COFs (covalent organic frameworks).

Solvent‐Free Encapsulation at High Pressure with Carboxylate‐Based MOFs

“…The solvent‐free encapsulation process carried out for the first time in this work can be considered as environmentally friendly, in line with others related to the synthesis of MOFs working in continuous mode, using water as a solvent or avoiding the use of solvents entirely , . We postulate that high pressure favors the diffusion of the additive into the material and therefore the use of any solvent is avoided.…”

“…The bibliography on the effect of high pressure on MOFs is very scarce. We have previously reported the solvent‐less synthesis of ZIF‐8 at high pressure and the behavior of this MOF at high pressure has also been described with regard to its stability, and water intrusion . Moreover, the contact of MOF Cu‐btc with several liquids (alcohols and perfluorotri‐ N ‐pentylamine) has been studied up to 8 GPa .…”

Large uniform copper 1,3,5-benzenetricarboxylate metal-organic-framework particles from slurry crystallization and their outstanding CO 2 gas adsorption capacity

“…Many white particles appear in the product ( Figure S1b, c and Figure S2f), implying the existence of impurity composed of unreacted ligand and unknown phase concluded from the XRD result. 31 Their FTIR spectra also exhibit some difference between them (Figure 4). Two obvious bands ascribing to the stretching vibrations of C=O (1709 cm −1 ) and C-O (1232 cm −1 ) labeled by dashed lines are observed for samples H-0.5 and H-0.25 (Figure 4e, f), which are the characteristic bands of ligand H3BTC.…”

High‐Pressure Synthesis of Metal–Inorganic Frameworks Hf4N20⋅N2, WN8⋅N2, and Os5N28⋅3 N2 with Polymeric Nitrogen Linkers

“…Although the synthesis of some porous materials may require high pressure (for example, ZIF‐8, hydrothermal synthesis of zeolites), the formation of porous structures at megabar pressures seems to be counterintuitive, as these conditions are expected to destabilize less dense framework structures. However, the pressures of about 110 GPa and temperatures of 2000 K are the conditions of the thermodynamic equilibrium between molecular and polymeric nitrogen, thus the volume gain of polymeric nitrogen is balanced by the energy of the triple nitrogen–nitrogen bond .…”