Jorge Flores

An alkaline one-pot metathesis reaction to give a [Cu3(BTC)2] MOF at r.t., with free Cu coordination sites and enhanced hydrogen uptake properties

A one-pot metathesis reaction between trimesic acid sodium salt and Cu(NO3)2 to yield [Cu3(BTC)2] (HKUST-1) in moderate to good yields, even at room temperature (r.t.) is presented, herein, for the first time. To determine if the basic nature of the metathesis reaction afforded any new physicochemical properties to HKUST-1, three variables were monitored: a) the energy source either from i) ultrasound (US), ii) stirring at room temperature (SRT) or iii) solvothermal (ST) treatment, b) the reaction solvent and c) the reaction time. The metathesis reaction provided DMF·H2O, EtOH·H2O or MeOH·H2O solvates. The compounds were thoroughly characterized by FTIR, XRD, nitrogen adsorption BET surface areas and TGA/DSC data, which indicated the formation of [Cu3(BTC)2] MOFs in eight out of ten synthetic entries. Low-pressure hydrogen uptake experiments revealed values as high as 2.44 wt% for the [Cu3(BTC)2] EtOH·H2O solvates. The [Cu3(BTC)2] MeOH·H2O and [Cu3(BTC)2] EtOH·H2O solvates possess high surface areas, the latter being the metathesis prepared MOF with the least H2O→Cu coordination according to TGA, DSC and a thermal desorption gas chromatography–mass spectrometry (GC-MS) coupled technique. This resulted in a material with less chemisorbed H2O and better H2 adsorption capability.

CLEAN-UP OF WASTES FROM THE TEXTILE INDUSTRY USING ANIONIC CLAYS

Toxic dyes must be removed from waste water coming from the textile and paint industries. Adsorption is one possible method of removing dyes under ‘soft’ conditions, without the generation of secondary hazardous materials. The present study used the carbonate-containing layered double hydroxides (LDH), Mg-Al and Mg-Zn-Al (with a M2+/M3+ ratio of 3), as adsorbents to remove two industrial colorants, Astrazon Remazol Brilliant Blue and Direct Red, present in low concentrations in aqueous solutions. The physicochemical properties of adsorbents at the surfaces of LDH, as well as the properties of the solutions containing the dyes control how the colorants are removed. Both fresh and calcined LDH were effective in the removal experiments, with effectiveness ranging from 50 to 100%. Analysis of kinetic data demonstrated that the adsorption process fitted the pseudo-second-order model better than the pseudo-first order model, information which is useful for system design in the treatment of wastes from the textile industry. Parameters such as pH of solutions and concentration of dye in solution influenced mainly the initial adsorption rate.

Organic biocides hosted in layered double hydroxides: enhancing antimicrobial activity

Abstract Samples of layered double hydroxides containing carbonates as compensating anions were prepared by the urea method. These LDHs were used as hosts of anions coming from pipemidic and nalidixic acid. XRD results confirm that these anions were hosted in the interlayer space of LDHs. Further, from 27Al NMR MAS characterization of an interaction between the brucite-like layers and anions was suggested. Then the hybrids LDHs were used as biocide of Salmonella typhi and Escherichia coli. The release profile of pipemidic and nalidixic anions from hybrid LDHs occurs for periods as long as 3.5 hours. The free-organic acid LDHs were not able to kill S. Typhi, neither E. coli. In contrast, the hybrids LDHs eliminate almost completely bacteria within short times.

Highly Basic and Dipolar Layered Double Hydroxides Enhance Catalysis of Cyanoethylation of Alcohols

Layered double hydroxides (LDH), magnesium–aluminum–carbonates and magnesium–gallium–aluminum–carbonates, were synthesized by sol–gel incorporating during synthesis a part of aluminum as (AlF6)3− blocks in order to incorporate F− as a part of brucite-like layers and not as compensating anions. Structural, textural and surface properties of resulting fluorinated were characterized. Particularly, presence the fluorine as a part of brucite-like layers influenced directly polarity and hydrogen bonding acceptor character at surface of materials. These modifications at surface of LDH greatly changed their catalytic properties. Cyanoethylation reaction between acrylonitrile and methanol was catalyzed by both fluorine-free and fluorinated LDH, pointing out a clear influence of fluorine on the conversion and rate reaction.Graphical Abstract