Mirtha A. O. Lourenço

Synthesis of New Metalloporphyrin Triads: Efficient and Versatile Tripod Optical Sensor for the Detection of Amines

Zinc and manganese complexes of porphyrin triads have been synthesized and are shown to be efficient as highly sensitive and selective tripod optical sensors for amines at the picomolar level.

Microwave assisted N-alkylation of amine functionalized crystal-like mesoporous phenylene-silica

N-alkylation reaction of amine functionalized phenylene moieties in crystal-like mesoporous silica is successfully achieved with about 87% of conversion in two reaction cycles. A potassium iodide catalyzed method commonly used for the selective N-monoalkylation of aniline is adapted and optimized to the N-monoalkylation reactions of the amine functionalized periodic mesoporous phenylene-silica (NH2-PMO) under microwave irradiation with preservation of the ordered mesostructure and of the crystal-like molecular scale periodicity of the material. This functionalization opens an avenue for the preparation of new materials with different amino-alkyl groups specially designed for a desired application, namely on the adsorption or catalytic fields.

Turning periodic mesoporous organosilicas selective to CO2/CH4 separation: deposition of aluminium oxide by atomic layer deposition

Nowadays, CO2/CH4 separation is considered extremely important with respect to making biogas economically viable. The search for efficient materials for biogas upgrading is at the cutting edge of research in the field of energy. Periodic mesoporous organosilicas (PMO) are highly suitable for application as selective adsorbents for CO2 as they have concomitant high specific surface areas and tunable surface properties. Herein, we describe the tuning of the surface properties of phenylene-PMO using atomic layer deposition (ALD) to add active aluminium species to the walls of these organic–inorganic hybrid materials. Modification with aluminium oxide was attained by varying the numbers of deposition cycles (from 2 to 100 cycles). A clear correlation between the amount of aluminium attached to PMO and the number of deposition cycles is observed. Consequently, an increase in the number of deposition cycles resulted in a reduction of the specific surface area and the pore volume of the PMO material. Variation of the number of deposition cycles to modify the surface of the PMOs yields composite materials with aluminium sites having different local coordination but the meso- and molecular-scale periodicity orders of the parent PMO remain intact. Adsorption results indicate that high selectivity for CO2/CH4 separation is obtained when pentacoordinated (AlV) and tetrahedral (AlIV) aluminium oxide are present in the PMO.

Optimization of the time and temperature of the microwave-assisted amination of phenylene-PMO

In this paper we report a study on the optimization of the amination of periodic mesoporous phenylene–silica (PMO) using microwave heating. The optimization was carried out for two key steps in the reaction, namely, (1) nitration of the bissilylated phenylene bridge, and (2) reduction of the nitro group to a primary amine. The temperatures of both reaction steps were varied between 37, 60, 75 and 90 °C. The reaction times studied were between 15 to 360 minutes. Microwave heating lead to significant reduction in the reaction times needed to achieve the maximum degree of nitration and amination compared to conventional means. After 15 minutes of reaction at 60 °C, a nitrogen density similar to that obtained for the same material synthesized conventionally was observed, and after 240 minutes of reaction time at 60 °C the nitrogen density was exceeded. A complete reduction of the nitro to the amine groups was observed after 15 minutes of reaction at 60 °C, which demonstrates the great potential of microwave irradiation in enhancing the kinetics of the post-synthesis functionalization of PMO materials, while preserving the molecular and mesoporous orders.