Transition Metal Single Atoms Constructed by Using Inherent Confined Space

Abstract

Single-atom catalysts (SACs) show expressively enhanced activity toward diverse reactions due to maximized atomic utilization of metal sites, while their facile, universal, and massive preparation remains a pronounced challenge. Here we report a facile strategy for the preparation of SACs by use of the inherent confined space between the template and silica walls in template-occupied mesoporous silica SBA-15 (TOS). Different transition metal precursors can be introduced into the confined space readily by grinding, and during succeeding calcination single atoms are constructed in the form of M−O− Si (M = Cu, Co, Ni, and Zn). In addition to the generality, the present strategy is easy to scale up and can allow the synthesis of 10 g of SACs in one pot through ball milling. The Cu SAC has been applied for CO 2 cycloaddition of epichlorohydrin, and the activity is obviously higher than the counterpart prepared without confined space and various reported Cu-containing catalysts.

Electronic properties and carrier mobilities of nanocarbons formed by non-benzoidal building blocks

“…46 Many other non-graphitic semiconducting nanoribbons have been studied in the literature, especially with many examples of synthesized systems. 31,46,67,68 Up to this point, we have not considered the spin degree of freedom. The presence of flat bands around the Fermi level Table 1 Width (in Å), electronic band gap (in eV), elastic constant (in eV Å À1 ), effective masses (in terms of the electron mass at rest -m 0 ), deformation potentials (in eV), and carrier mobilities (in cm 2 V À1 s À1 ) for AGNRs, phpNRs, and popNRs and/or edge states is an indication of the possible existence of spin-polarized configurations.…”

Fabrication of Fe Single Atoms by Utilizing the Inherent Confined Space for Phenol Hydroxylation

“…Carriers are known to play a vital role in the synthesis of catalysts, and SBA-15 is an ideal choice of carrier because of its rich porosity and surface modifiability. − Template-free SBA-15 (TFS) is obtained by removing the template in the TOS after calcination and is usually used as the carrier for functionalization (Figure ). Actually, the existence of inherent confined space in the TOS may restrict the aggregation of metals and even yield single atoms ideally . By simple solid phase grinding and subsequent calcination, the precursor Fe­(NO 3 ) 3 was easily introduced into inherent confined space.…”

“…29 Actually, the existence of inherent confined space in the TOS may restrict the aggregation of metals and even yield single atoms ideally. 30 By simple solid phase grinding and subsequent calcination, the precursor Fe(NO 3 ) 3 was easily introduced into inherent confined space. Density functional theory (DFT) and experimental results demonstrate that Fe single atoms form a covalent Fe−O−Si structure with the carrier.…”

Poly(2-vinylpyridine)/MCM-41 Composites with Micropores and Switchable Mesopores for the Removal of Cr(VI)

“…), polymers (polyethyleneimine, 15 polyamidoamine, 16 etc. ), and inorganics (single atoms, 17 metal oxide, 18 etc.) have been used to modify mesoporous silica to improve its application performances.…”

“…Therefore, the reversible opening and closing of mesopores are necessary during adsorption. The introduction of stimuli–response polymers or organic molecules could endow porous material with an adjustable porous structure. , For instance, thermal-controlled poly­( N -isopropylacrylamide) and light-responsive azobenzene − were introduced into the pores of MCM-41 and their pore size could generate reversible change by the regulation of temperature or light irradiation. However, these modifiers are both located inside the pores, and they could not control the opening or closing of mesopores.…”