A Green Selective Water-Etching Approach to MOF@Mesoporous SiO2 Yolk-Shell Nanoreactors with Enhanced Catalytic Stabilities

Abstract

To improve the stability of MOF catalysts, a design of MOF@mesoporous SiO 2 yolk-shell nanoreactors was developed via a mesoporous silica coating followed by selective water-etching strategy. Benefiting from their permeable mesoporous SiO 2 shells, exposed active sites on MOF surfaces, and protective shells, the yolkshell nanoreactors exhibit higher catalytic stability than bare MOF crystals in CO 2 cycloaddition, with product yield remaining unchanged upon three cycles.

Encapsulating Sulfides into Tridymite/Carbon Reactors Enables Stable Sodium Ion Conversion/Alloying Anode with High Initial Coulombic Efficiency Over 89%

“…Such similar shelly mesoporous nature for SiO 2 has been also confirmed by recent works for CO 2 cycloaddition catalysis. [ 38 ]…”

“…: ≈165.8 Wh kg −1 ) is superior to the ones reported in pioneering literatures, such as GeS 2 //Na 3 V 2 (PO 4 ) 2 O 2 F, SnS 2 @G//Na 3 V 2 (PO 4 ) 3 , Sb‐O‐G//Na 3 V 2 (PO 4 ) 3 , Sn 2 P 2 O 7 /RGO// Na 3 V 2 (PO 4 ) 3, MoSe 2 /N,P‐rGO//Na 3 V 2 (PO 4 ) 3 /C, Sb@TiO 2 //Na 3 V 2 (PO 4 ) 3 , or even much close to the level for advanced PNA//Na 1.5 VPO 4.8 F 0.7 . [ 18,38–48 ] Figure 6f displays the Max. specific capacity and energy when cells proceed after 200 times of cycling at respective current rates.…”

Mesoporous Silica Encapsulated Metal-Organic Frameworks for Heterogeneous Catalysis

“…The MOF@mSiO 2 -YS has also been applied in catalytic cycloaddition of CO 2 to styrene oxide with tetrabutylammonium bromide as a cocatalyst. 4 It has been found that active species of this nanoreactor-like catalyst are only from Cr 3+ Lewis acid sites of MIL-101(Cr) nanocrystals and both catalytic activity and chemical stability of MIL-101(Cr) are improved owing to fully exposed active yolk surfaces and permeable mSiO 2 shell for the reactants and products. Furthermore, the protective role of the rigid mSiO 2 shell has also been elucidated because it could slow down the decomposition of MIL-101(Cr) nanocrystals encapsulated during the cycloaddition reactions.…”

“…3 In this issue of Matter, Yu et al have reported a new development of MOF@mSiO 2 yolk-shell nanostructure, in which MIL-101(Cr) nanocrystals serve as the yolk and mSiO 2 as the protecting shell. 4 The synthetic route they investigated is depicted in Scheme 1. Briefly, MIL-101(Cr) nanocrystals are first wrap-ped with a shell of mSiO 2 using silica source tetraethyl orthosilicate (TEOS) and colloidal template cetyltrimethylammonium bromide (CTAB).…”

“…The future work is planned to optimize the synthesis parameters and improve the uniformity of the nanoreactors, which will hopefully further enlarge the family of this kind of MOF-based yolk-shell nanocatalysts. 4 In terms of heterogeneous catalysis, both external surface area and internal porosity of single-crystalline MOFs play a crucial role in their actual catalytic performance. 3 The above etching transformation of core-shell construct to yolkshell configuration apparently brings the benefit of easing transport processes of reacting molecules and diffusing reaction products, 2 since the blockage of active sites between core and shell can be circumvented by creating an interfacial space between them and ensuring fully exposed surfaces of nanocrystal yolk (Step 3, Scheme 1).…”