using supercritical co2 in the preparation of metal organic frameworks investigating effects on crystallisation: Investigating effects on crystallisation

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 °Ϲ). The objective of the work was to see if the sames or different products would result from the ssCO2 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.