Boosting the Catalytic Performance of Metal–Organic Frameworks for Steroid Transformations by Confinement within a Mesoporous Scaffold

Abstract

Solid-state crystallization achieves selective confinement of metal-organic framework (MOF) nanocrystals within mesoporous materials,t herebyr endering active sites more accessible compared to the bulk-MOF and enhancing the chemical and mechanical stability of MOF nanocrystals. (Zr)UiO-66(NH 2 )/SiO 2 hybrid materials were tested as efficient and reusable heterogeneous catalysts for the synthesis of steroid derivatives,o utperforming the bulk (Zr)UiO-66(NH 2 ) MOF.Aclear correlation between the catalytic activity of the dispersed Zr sites present in the confined MOF,and the loading of the mesoporous SiO 2 ,i sd emonstrated for steroid transformations.Scheme 1. Transformations of testosterone((a) and (b)) and epiandrosterone((c) and (d)) steroids involving the activation of carbonyl groups. Stoichiometric [9a,k] or catalytic conditions [8b, 9g] employed.

Recent Advances of MOFs and MOF‐Derived Materials in Thermally Driven Organic Transformations

“…[15e, 38] As an example, in 2017, De Vos et al prepared a( Zr)UiO-66(NH 2 )/SiO 2 hybrid materialt hrough the confinemento fM OF nanocrystals within am esoporous silica known as SBA-15 ( Figure 9). [39] To load the nanocrystals inside the template channels, as olution containing the MOF precursors was infused into the mesoporous material via wet impregnationf ollowed by at hermal treatment to form the desired MOF and as ubsequentw ashing to remover esidual starting materials. Not only were the hexanuclear Zr 4 + active sites more accessible, but the mesoporousS BA-15 provided protection to MOF nanocrystals enhancingt heir chemical and mechanical stability all while inhibiting leaching of the Zr 4 + .T he combination of these phenomena endowed the (Zr)UiO-66(NH 2 )/SiO 2 composites with better catalytic performance in (D) SOM-ZIF-8 for Knoevenagel condensationreactionsbetween malononitrile and benzaldehydes.…”

“…Confinement of the UiO-66 MOF nanocrystals inside the pores of SBA-15,amesoporous silica, whichw as used to promote MOF-catalyzed transformations of bulkysteroids. [39] esterification reactions used to produce various steroid derivatives when compared to the bulk (Zr)UiO-66(NH 2 )M OF in both batch and continuous flow experiments.…”

“…This was highlighted by the aforementionedw ork of De Vosw ith his co-authors, who made (Zr)UiO-66(NH 2 )/SiO 2 through the confinement of MOF nanocrystals within am esoporouss ilica known as SBA-15. [39] Then, in 2018, Li's study placed aM OF precursor inside am esoporouss ilica, known as KIT-6. Thisl ed to ultrafinem etal-oxide NPs after subsequent calcination ( Figure 21).…”

Synthesis of Fluidized CO2 Sorbents Based on Diamine Coordinated to Metal–Organic Frameworks by Direct Conversion of Metal Oxides Supported on Mesoporous Silica

“…[4] Recently,o ur group has reported ag eneral approachf or confining MOF nanocrystals within mesoporousm aterials through solid-state synthesis, such as silica, alumina, carbon, or polymer. [5] Shaping MOF nanocrystals into more functional materials resulted in an upgrade of some of their features, such as enhanced attritionr esistance, excellent handling,g ood fluidizability,a nd hierarchical meso/micro-porosity.F or some interesting industrial applications, such as catalysis [6] and CO 2 capture, [7] which are currently being studiedin our group, an en-hancement of the performance compared to alternative technologiesi so bserved.I nt he same way,w er eport herein another alternative approach, adapting the methodo fg rowing MOFsd irectly from metal oxides for shapingM OFs into fluidized CO 2 solid sorbents by direct conversion of supported metalo xidesinto supported MOFs.Currently,s everal metal and metal oxides( insoluble metal precursors) can be efficiently converted into metal-organic frameworks by chemical etching with conventionalo rganic ligandsw ithoutc ompromising eithert he high crystallinity or the elevated surface area. [8] This conversion can be done in a records ynthesis time (few minutes [9] ), mild temperatures (room temperature [10] ), reduced amount of solvents (event undera bsence or gas phase [11] ), and producing water as concomitantr esidue, thus avoiding the acidic side-products or undesired salt anions.…”

“…[4] Recently,o ur group has reported ag eneral approachf or confining MOF nanocrystals within mesoporousm aterials through solid-state synthesis, such as silica, alumina, carbon, or polymer. [5] Shaping MOF nanocrystals into more functional materials resulted in an upgrade of some of their features, such as enhanced attritionr esistance, excellent handling,g ood fluidizability,a nd hierarchical meso/micro-porosity.F or some interesting industrial applications, such as catalysis [6] and CO 2 capture, [7] which are currently being studiedin our group, an en-hancement of the performance compared to alternative technologiesi so bserved.I nt he same way,w er eport herein another alternative approach, adapting the methodo fg rowing MOFsd irectly from metal oxides for shapingM OFs into fluidized CO 2 solid sorbents by direct conversion of supported metalo xidesinto supported MOFs.…”