Is there any microporosity in ordered mesoporous silicas?
The porous structure of nanostructured silicas MCM-41 and SBA-15 has been characterized using N2 adsorption at 77 K, before and after n-nonane preadsorption, together with immersion calorimetry into liquids of different molecular dimensions. Selective blocking of the microporosity with n-nonane proves experimentally that MCM-41 is exclusively mesoporous while SBA-15 exhibits both micro- and mesopores. Additionally, N2 adsorption experiments on the preadsorbed samples show that the microporosity on SBA-15 is located in intrawall positions, the micropore volume accounting for only approximately 7-8 % of the total pore volume. Calorimetric measurements into n-hexane (0.43 nm), 2-methylpentane (0.49 nm), and 2,2-dimethylbutane (0.56 nm) estimate the size of these micropores to be < or = 0.56 nm.
Silvestre-Alberto
A
A
Laboratorio de Materiales Avanzados, Departamento de Química Inorgánica, Universidad de Alicante, Ap. 99, E-03080 Alicante, Spain.
Jardim
E O
EO
Bruijn
E
E
Meynen
V
V
Cool
P
P
Sepulveda-Escribano
A
A
Silvestre-Alberto
J
J
Rodriguez-Reinoso
F
F
D000327:Adsorption; D000473:Alkanes / Q000737:chemistry; D002151:Calorimetry; D049329:Nanostructures / Q000737:chemistry; D009584:Nitrogen / Q000737:chemistry; D016062:Porosity; D012822:Silicon Dioxide / Q000138:chemical synthesis / Q000737:chemistry*; D013499:Surface Properties
D000473:Alkanes; C509968:MCM-41; C509969:SBA-15; D012822:Silicon Dioxide; D009584:Nitrogen; C017573:nonane