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Effects of ammonium hydroxide on the structure and gas adsorption of nanosized Zr-MOFs (UiO-66).

Nanoscale (2012-04-26)
Hussein Rasool Abid, Ha Ming Ang, Shaobin Wang
ABSTRACT

Several zirconium-based metal-organic frameworks (Zr-MOFs) have been synthesized using ammonium hydroxide as an additive in the synthesis process. Their physicochemical properties have been characterized by N(2) adsorption/desorption, XRD, SEM, FTIR, and TGA, and their application in CO(2) adsorption was evaluated. It was found that addition of ammonium hydroxide produced some effects on the structure and adsorption behavior of Zr-MOFs. The pore size and pore volume of Zr-MOFs were enhanced with the additive, however, specific surface area of Zr-MOFs was reduced. Using an ammonium hydroxide additive, the crystal size of Zr-MOF was reduced with increasing amount of the additive. All the samples presented strong thermal stability. Adsorption tests showed that capacity of CO(2) adsorption on the Zr-MOFs under standard conditions was reduced due to decreased micropore fractions. However, modified Zr-MOFs had significantly lower adsorption heat. The adsorption capacity of carbon dioxide was increased at high pressure, reaching 8.63 mmol g(-1) at 987 kPa for Zr-MOF-NH(4)-2.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Ammonium hydroxide solution, ACS reagent, 28.0-30.0% NH3 basis
Sigma-Aldrich
Ammonium hydroxide solution, 28% NH3 in H2O, ≥99.99% trace metals basis
Sigma-Aldrich
Ammonium hydroxide solution, puriss., 30-33% NH3 in H2O
Sigma-Aldrich
Ammonium hydroxide solution, BioUltra, ~1 M NH3 in H2O (T)
Sigma-Aldrich
Ammonium hydroxide solution, puriss. p.a., reag. ISO, reag. Ph. Eur., ~25% NH3 basis
Sigma-Aldrich
Ammonium hydroxide solution, puriss., meets analytical specification of Ph. Eur., 25-30% NH3 basis
Sigma-Aldrich
Ammonium hydroxide solution, puriss. p.a. plus, ≥25% NH3 in H2O