Publications by authors named "Angel E Lozano"

5 Publications

  • Page 1 of 1

Gas Separation by Mixed Matrix Membranes with Porous Organic Polymer Inclusions within -Hydroxypolyamides Containing -Terphenyl Moieties.

Polymers (Basel) 2021 Mar 18;13(6). Epub 2021 Mar 18.

Surfaces and Porous Materials (SMAP), Associated Research Unit to CSIC, Faculty of Science, University of Valladolid, Paseo Belén 7, 47011 Valladolid, Spain.

A hydroxypolyamide (HPA) manufactured from 2,2-bis(3-amino-4-hydroxy phenyl)-hexafluoropropane (APAF) diamine and 5'-terbutyl--terphenyl-4,4''-dicarboxylic acid chloride (tBTpCl), and a copolyimide produced by stochiometric copolymerization of APAF and 4,4'-(hexafluoroisopropylidene) diamine (6FpDA), using the same diacid chloride, were obtained and used as polymeric matrixes in mixed matrix membranes (MMMs) loaded with 20% (/) of two porous polymer networks (triptycene-isatin, PPN-1, and triptycene-trifluoroacetophenone, PPN-2). These MMMs, and also the thermally rearranged membranes (TR-MMMs) that underwent a thermal treatment process to convert the o-hydroxypolyamide moieties to polybenzoxazole ones, were characterized, and their gas separation properties evaluated for H, N, O, CH, and CO. Both TR process and the addition of PPN increased permeability with minor decreases in selectivity for all gases tested. Excellent results were obtained, in terms of the permeability versus selectivity compromise, for H/CH and H/N separations with membranes approaching the 2008 Robeson's trade-off line. The best gas separation properties were obtained when PPN-2 was used. Finally, gas permeation was characterized in terms of chain intersegmental distance and fraction of free volume of the membrane along with the kinetic diameters of the permeated gases. The intersegmental distance increased after TR and/or the addition of PPN-2. Permeability followed an exponential dependence with free volume and a quadratic function of the kinetic diameter of the gas.
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http://dx.doi.org/10.3390/polym13060931DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8003052PMC
March 2021

Porous Organic Polymers Containing Active Metal Centers for Suzuki-Miyaura Heterocoupling Reactions.

ACS Appl Mater Interfaces 2020 Dec 11;12(51):56974-56986. Epub 2020 Dec 11.

IU CINQUIMA, Universidad de Valladolid, Paseo Belén 5, E-47011 Valladolid, Spain.

A new generation of confined palladium(II) catalysts covalently attached inside of porous organic polymers (POPs) has been attained. The synthetic approach employed was straightforward, and there was no prerequisite for making any modification of the precursor polymer. First, POP-based catalytic supports were obtained by reacting one symmetric trifunctional aromatic monomer (1,3,5-triphenylbenzene) with two ketones having electron-withdrawing groups (4,5-diazafluoren-9-one, DAFO, and isatin) in superacidic media. The homopolymers and copolymers were made using stoichiometric ratios between the functional groups, and they were obtained with quantitative yields after the optimization of reaction conditions. Moreover, the number of chelating groups (bipyridine moieties) available to bind Pd(II) ions to the catalyst supports was modified using different DAFO/isatin ratios. The resulting amorphous polymers and copolymers showed high thermal stability, above 500 °C, and moderate-high specific surface areas (from 760 to 935 m g), with high microporosity contribution (from 64 to 77%). Next, POP-supported Pd(II) catalysts were obtained by simple immersion of the catalyst supports in a palladium(II) acetate solution, observing that the metal content was similar to that theoretically expected according to the amount of bipyridine groups present. The catalytic activity of these heterogeneous catalysts was explored for the synthesis of biphenyl and terphenyl compounds, via the Suzuki-Miyaura cross-coupling reaction using a green solvent (ethanol/water), low palladium loads, and aerobic conditions. The findings showed excellent catalytic activity with quantitative product yields. Additionally, the recyclability of the catalysts, by simply washing it with ethanol, was excellent, with a sp-sp coupling yield higher than 95% after five cycles of use. Finally, the feasibility of these catalysts to be employed in tangible organic reactions was assessed. Thus, the synthesis of a bulky compound, 4,4'-dimethoxy-5'--butyl--terphenylene, which is a precursor of a thermal rearrangement monomer, was scaled-up to 2 g, with high conversion and 96% yield of the pure product.
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http://dx.doi.org/10.1021/acsami.0c16184DOI Listing
December 2020

Microporous Polymer Networks for Carbon Capture Applications.

ACS Appl Mater Interfaces 2018 Aug 24;10(31):26195-26205. Epub 2018 Jul 24.

Department of Applied Macromolecular Chemistry, Instituto de Ciencia y Tecnología de Polímeros, ICTP-CSIC , Juan de la Cierva 3 , E-28006 Madrid , Spain.

A new generation of porous polymer networks has been obtained in quantitative yield by reacting two rigid trifunctional aromatic monomers (1,3,5-triphenylbenzene and triptycene) with two ketones having electron-withdrawing groups (trifluoroacetophenone and isatin) in superacidic media. The resulting amorphous networks are microporous materials, with moderate Brunauer-Emmett-Teller surface areas (from 580 to 790 m g), and have high thermal stability. In particular, isatin yields networks with a very high narrow microporosity contribution, 82% for triptycene and 64% for 1,3,5-triphenylbenzene. The existence of favorable interactions between lactams and CO molecules has been stated. The materials show excellent CO uptakes (up to 207 mg g at 0 °C/1 bar) and can be regenerated by vacuum, without heating. Under postcombustion conditions, their CO/N selectivities are comparable to those of other organic porous networks. Because of the easily scalable synthetic method and their favorable characteristics, these materials are very promising as industrial adsorbents.
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http://dx.doi.org/10.1021/acsami.8b05854DOI Listing
August 2018

Soluble, microporous, Tröger's Base copolyimides with tunable membrane performance for gas separation.

Chem Commun (Camb) 2016 Mar;52(19):3817-20

Department of Energy Engineering, College of Engineering, Hanyang University, Seoul 04763, Republic of Korea.

A facile two-step synthesis beginning with commercial monomers to prepare copolyimides by Tröger's Base (TB) formation provides membranes for the first time with tunable gas transport relative to hydrogen separations, CO2 plasticization resistance, and good mechanical and thermal properties.
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http://dx.doi.org/10.1039/c5cc09783eDOI Listing
March 2016

Reactivity of the 4-amino-5H-1,2-oxathiole-2,2-dioxide heterocyclic system: a combined experimental and theoretical study.

Chemistry 2008 ;14(31):9620-32

Instituto de Química Médica (C.S.I.C.), C/Juan de la Cierva 3, 28006 Madrid (Spain).

The reactivity of the 4-amino-5H-1,2-oxathiole-2,2-dioxide (or beta-amino-gamma-sultone) heterocyclic system has scarcely been studied. Here we describe the reactivity of this system towards electrophiles and amines on readily available model substrates differently substituted at the C-5 position. A variety of C-electrophiles, carbonyl electrophiles (such as acyl chlorides, isocyanates, or aldehydes) and halogen or nitrogen electrophiles have been explored. Both the C-3 and 4-amino positions of the beta-amino-gamma-sultone system are able to undergo electrophilic reactions, and the reaction products depend on the electrophile used and on the reaction conditions. On the other hand, nucleophilic attack of amines occurs at the C-4 position of the beta-amino-gamma-sultone system only in spiranic substrates bearing alicyclic substituents at the C-5 position. A comparative computational study between spiranic and non-spiranic substrates suggests that conformational changes, undergone on intermediate compounds, account for the observed reactivity differences. Moreover, these conformational changes seem to bring about an increase of electron density on the N-4 and C-3 atoms of the enaminic system, and a possible enhancement in the reactivity of spiranic substrates towards electrophiles in the presence of amines. Experimental data consistent with this predicted enhanced reactivity is also presented.
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http://dx.doi.org/10.1002/chem.200800433DOI Listing
December 2008