Naphthalene Tetrazole-Based Nickel Metal-Organic Framework as a Filler of Polycarbonate Membranes to Improve CO2 and H2 Separation.

A tetrazole-naphthalene linker was used to prepare a nickel MOF (metal-organic framework) (NiNDTz) with interesting properties: a specific surface area SBET of 320 m2g-1 (SLangmuir 436 m2g-1), high thermal stability (Tdonset = 300 °C), and CO2 uptake of 1.85 mmolg-1, attributed to the tetrazole groups to be used as fillers in gas separation membranes. The role of these groups was crucial in the mechanical properties of mixed membranes prepared using polycarbonate as a polymer matrix, providing a very homogeneous filler distribution and also in the gas separation properties since a simultaneous increase in permeability and selectivity was achieved, especially in the hybrid membrane containing 20% filler (PC@NiNDTz-20%). This membrane exhibited an excellent balance between permeability (P) and selectivity (α) with an increase in the permeability of CO2 and H2, 177 and 185%, respectively, and improvements in the selectivity of these gases against greenhouse gases such as methane and ethylene (between 15 and 28% improvement). These results make this membrane competitive to deal with separations in which these gases are involved, and are of special interest for the H2/CH4 separation since it clearly improves the performance of pure PC and no better PC-based membranes have been reported in the literature for this separation.

BINOL-Containing Chiral Porous Polymers as Platforms for Enantiorecognition.

The enantioselective discrimination of racemic compounds can be achieved through the design and preparation of a new family of chiral conjugated BINOL-porous polymers (CBPPs) from enantiopure (R)- or (S)-BINOL derivatives and 1,3,5-tris(4-phenylboronic acid)benzene or 1,3,5-tris(4-ethynylphenyl)benzene, 1,3,5-triethynyl-2,4,6-trifluorobenzene, and tetra(4-ethynylphenyl)methane as comonomers following Suzuki-Miyaura and Sonogashira-Hagihara carbon-carbon coupling approaches. The obtained CBPPs show high thermal stability, a good specific surface area, and a robust framework and can be applied successfully in the fluorescence recognition of enantiomers of terpenes (limonene and α-pinene) and 1-phenylethylamine. Fluorescence titration of CBPPs-OH in acetonitrile shows that all Sonogashira hosts exhibit a preference for the (R)-enantiomer over the (S)-enantiomer of 1-phenylethylamine, the selectivity being much higher than that of the corresponding BINOL-based soluble system used as a reference. However, the Suzuki host reveals a preference toward (S)-phenylethylamine. Regarding the sensing of terpenes, only Sonogashira hosts show enantiodifferentiation with an almost total preference for the (S)-enantiomer of limonene and α-pinene. Based on the computational simulations and the experimental data, with 1-phenylethylamine as the analyte, chiral recognition is due to the distinctive binding affinities resulting from N···H-O hydrogen bonds and the π-π interaction between the host and the guest. However, for limonene, the geometry of the adsorption complex is mostly governed by the interaction between the hydroxyl group of the BINOL unit and the C═C bond of the iso-propenyl fragment. The synthetic strategy used to prepare CBPPs opens many possibilities to place chiral centers such as BINOL in porous polymers for different chiral applications such as enantiomer recognition.

Thiol-yne chemistry of diferrocenylacetylene: from synthesis and electrochemistry to theoretical studies.

The thiol-yne coupling chemistry of diferrocenylacetylene (FcCCFc) 1, bearing two electron rich and redox-active ferrocenyl units (Fc = Fe(η5-C5H4)(η5-C5H5)) and an internal triple bond, has been investigated for the first time. In order to determine whether steric limitations might affect hydrothiolation, a model reaction using a functionalized monothiol was tested, namely 2-mercaptoethanol I. The thiol-diferrocenylacetylene reactions were initiated either thermally (in toluene with AIBN) or by UV light irradiation (in THF and in the presence of DMPA as the photoinitiator). The outcomes of these thiol-yne reactions showed a strong dependence on the initiation method used, with the thermally initiated one being the most efficient. These thiol-diferrocenylacetylene reactions mainly afforded the (Z)-stereoisomer of the newly obtained vinyl thioether sulfide FcCHC(Fc)S-(CH2)2OH (2), unlike the more common (E)-vinyl sulfides found in other additions to alkynes. The hydrothiolation of the internal -CC- bond in 1 was successfully extended to dithiol 2,2'-(ethylenedioxy)diethanethiol II, leading to the formation of the (ZZ)-isomer, with four ferrocenyl units, as the major product. According to the electrochemical studies, the new asymmetrical ferrocenyl-vinyl sulfides show iron-iron electronic and electrostatic interactions. Theoretical results for the (Z)-stereoisomer (2) suggest that adiabatic oxidation would lead to the loss of almost one electron on the ferrocenyl subunit closer to the thioether chain. Furthermore, the thiol-yne chemistry of the internal -CC- bond in diferrocenylacetylene has been compared to the external triple bond in ethynylferrocene, the theoretical results of which helped us to rationalize the very different reactivities observed in both metallocenes.

Conversion of CO2 into Chloropropene Carbonate Catalyzed by Iron (II) Phthalocyanine Hypercrosslinked Porous Organic Polymer.

Commercial iron (II) phthalocyanine (FePc) was knitted with biphenyl using a Friedel-Crafts reaction to yield a micro-meso porous organic polymer (FePc-POP) with a specific surface area of 427 m2/g and 5.42% of iron loading. This strategy allowed for the direct synthesis of a heterogeneous catalyst from an iron containing monomer. The catalytic system, formed by the knitted polymer containing FePc and DMAP (4-dimethylamino pyridine) as base, results in an efficient heterogeneous catalyst in the cycloaddition of CO2 to epichlorohydrin to selectively obtain the corresponding cyclic carbonate. Thus, a TON (mmol substrate converted/mmol catalysts used) value of 2700 was reached in 3 h under mild reaction conditions (solvent free, 90 °C, 3 bar of CO2). The catalyst does not exhibit leaching during the reactions, which was attributed to the excellent stability of the metal in the macrocycle.

Iron Phthalocyanine-Knitted Polymers as Electrocatalysts for the Oxygen Reduction Reaction.

Knitted iron phthalocyanine-based porous polymer networks (K-FePcs) were prepared in a single step using solvent-knitting strategies with commercial iron phthalocyanine as a building monomer. The incorporation of different aryl comonomers (biphenyl and 1,2,4,5-tetraphenylbenzene) to FePc allowed quantitative yields, high porosities, and excellent ORR activity. The reversible Fe(III)/Fe(II) redox potential of FeN4 centers of the knitted polymer networks in N2-saturated electrolyte solution (i.e., ∼0.8 V vs RHE) were shown as good descriptors of their ORR activity. K-FePc2Ph presented the highest amount of FeN4 active sites and an adequate degree of steric hindrance to maintain the isolation between catalytically active sites. Moreover, it displayed comparable current density limits and superior mass activity and half-wave potential (i.e., 0.88 V vs RHE) than those of 20% Pt/C benchmark catalyst, while keeping higher stability toward methanol oxidation. K-FePc2Ph can be an interesting alternative to Pt-based ORR electrocatalysts.