Using Supercritical CO2 in the Preparation of Metal-Organic Frameworks: Investigating Effects on Crystallisation

Abstract

In this report, we explore the use of supercritical CO2 (scCO2) in the synthesis of well-known metal-organic frameworks (MOFs) including Zn-MOF-74 and UiO-66, as well as on the preparation of [Cu24(OH-mBDC)24]n metal-organic polyhedra (MOPs) and two new MOF structures {[Zn2(L1)(DPE)]∙4H2O}n and {[Zn3(L1)3(4,4′-azopy)]∙7.5H2O}n, where BTC = benzene-1,3,5-tricarboxylate, BDC = benzene-1,4-dicarboxylate, L1 = 4-carboxy-phenylene-methyleneamino-4-benzoate, DPE = 1,2-di(4-pyridyl)ethylene, 4.4′-azopy = 4,4′- azopyridine, and compare the results versus traditional solvothermal preparations at low temperatures (i.e., 40 °C). The objective of the work was to see if the same or different products would result from the scCO2 route versus the solvothermal method. We were interested to see which method produced the highest yield, the cleanest product and what types of morphology resulted. While there was no evidence of additional meso- or macroporosity in these MOFs/MOPs nor any significant improvements in product yields through the addition of scCO2 to these systems, it was shown that the use of scCO2 can have an effect on crystallinity, crystal size and morphology.

Improved photodegradation of anionic dyes using a complex graphitic carbon nitride and iron-based metal–organic framework material

“…The heterostructure construction created by the interface between g-C3N4 and other porous materials can increase surface electrostatic interactions, achieve unique porosity and morphology, and can limit recombination of photogenerated electron-hole pairs, and is thus of broad and current interest. [36][37][38] To this extent, metal-organic frameworks (MOFs) with diverse chemical compositions, exceptional surface areas and tuneable porosity, [39][40][41][42] have gained increasing attention in recent years. Heterojunctions in composites of g-C3N4 with MOFs, formed by the π-π interactions between the aromatic and the triazine rings, can accelerate charge transfer across the interface and shortens the charge transport distance, thus enhancing separation rates of photoinduced electron-hole pairs.…”

Effect of mono- and divalent extra-framework cations on the structure and accessibility of porosity in chabazite zeolites

“…Post-synthetic modification for developing new forms of existing zeolites is a simple approach, which has also been seen in the related area of study of metal-organic frameworks. 44,45 Chabazite zeolites (CHA) which were heavily studied in the past have attracted the attention of the zeolite community because of their usefulness for a wide variety of applications. As mentioned previously, these chabazite zeolites have been widely reported as being efficient catalysts for chemical processes such as the conversion of methanol to olefins 46,47 and selective catalytic reduction of NOx.…”

Supercritical CO2 Directional‐Assisted Synthesis of Low‐Dimensional Materials for Functional Applications

“…Equally, as crystalline network polymers comprising lightweight elements linked together by covalent bonds, [204] COFs have attracted intense attention because of tunable porosity, large surface area, chemical modularity, low density, and exceptional stability, [205,206] which play a crucial role in the divergent practical applications including catalysis, separation, chemical detection, smart sensing, electrochemistry, energy storage, and drug delivery. [207][208][209][210][211][212] Unlike some research on crystallinity, crystal size, and morphology of MOFs synthesized by using SC CO 2 , [213][214][215] the use of SC CO 2 in the field of 2D COFs synthesis is still being explored. The single-crystal polymerization of 2D COFs can be accelerated by SC CO 2 and achieve a desirable surface area, compared to that of COF synthesized by solvothermal polymerization.…”