Organic Vapor Sorption in a High Surface Area Dysprosium(III)–Phosphine Oxide Coordination Material

Lanthanide-Organic Frameworks Featuring Three-Dimensional Inorganic Connectivity for Multipurpose Hydrocarbon Separation

Implementation of lanthanide-organic frameworks (LOFs) as solid adsorbents has been frequently handicapped by their permanent porosity being difficult to establish owing to the remarkable flexibility and diversity of lanthanide ions in terms of coordination number and geometry. Construction of robust LOFs with permanent porosity for industrially important hydrocarbon separation will greatly expand their application potential. In this work, by distributing N and O donors into an m-terphenyl skeleton, we rationally synthesized a heterofunctional linker, and constructed a pair of isostructural LOFs. Due to the inclusion of a rarely observed three-dimensional metal-carboxylate backbone serving as a highly connected inorganic secondary building unit, their permanent porosities were successfully established by diverse gas isotherms. They can be applied as separating media not only for natural gas purification and removal of carbon dioxide from C₂ hydrocarbons but also more importantly for single-step ethylene (C₂H₄) purification from a three-component C₂H_n mixture during the adsorption process. The latter separation is very challenging and has been less reported in the literature. This work provides a unique example of LOFs featuring three-dimensional inorganic connectivity applied to multipurpose hydrocarbon separations.

Metal-Organic Frameworks for Highly Selective Separation of Xylene Isomers and Single-Crystal X-ray Study of Aromatic Guest-Host Inclusion Compounds

Separation of hydrocarbon molecules, such as benzene/cyclohexane and o-xylene/m-xylene/p-xylene, is relevant due to their widespread application as chemical feedstock but challenging because of their similar boiling points and close molecular sizes. Physisorption separation could offer an energy-efficient solution to this problem, but the design and synthesis of sorbents that exhibit high selectivity for one of the hydrocarbons remain a largely unmet challenge. Herein, we report a new heterometallic MOF with a unique tortuous shape of channels decorated with aromatic sorption sites [Li₂Zn₂(bpy)(ndc)₃] (NIIC-30(Ph), bpy = 4,4'-bipyridine, ndc^2- = naphthalene-1,4-dicarboxylate) and study of its benzene/cyclohexane and xylene vapor and liquid separation. For an equimolar benzene/cyclohexane mixture, it is possible to achieve a 10-fold excess of benzene in the adsorbed phase. In the case of xylenes, microporous framework NIIC-30(Ph) demonstrates outstanding selective sorption properties and becomes a new benchmark for m-/o-xylene separation. In addition, NIIC-30(Ph) is stable enough to carry out at least three separation cycles of benzene/cyclohexane mixtures or ternary o-xylene/m-xylene/p-xylene mixtures both in the liquid and in the vapor phase. Insights into the performance of NIIC-30(Ph) are gained from X-ray structural studies of each aromatic guest inclusion compound.

Boronate Covalent and Hybrid Organic Frameworks Featuring PIII and P=O Lewis Base Sites

Two covalent organic frameworks comprising Lewis basic PIII centers and Lewis acidic boron atoms were prepared by poly-condensation reactions of newly obtained tris(4-diisopropoxyborylphenyl)phosphine with 2,3,6,7,10,11-hexahydroxytriphenylene and 2,3,6,7-tetrahydroxy-9,10-dimethylanthracene. Obtained materials exhibit significant sorption of dihydrogen (100 cm3  g-1 at 1 bar at 77 K), methane (20 cm3  g-1 at 1 bar at 273 K) and carbon dioxide (50 cm3  g-1 at 1 bar at 273 K). They were exploited as solid-state ligands for coordination of Pd0 centers. Alternatively, in a bottom-up approach, boronated phosphine was treated with Pd2 dba3 and poly-condensated, yielding hybrid materials where the polymer networks are formed by means of covalent boronate linkages and coordination P-Pd bonds. In addition, the analogous materials based on phosphine oxide were synthesized. The DFT calculations on framework-guest interactions revealed that the behavior of adjacent boron and phosphorus/phosphine oxide centers is reminiscent of that found in Frustrated Lewis Pairs and may improve sorption of selected molecules.

Exceptionally effective benzene/cyclohexane separation using a nitro-decorated metal-organic framework

Using a series of isoreticular MOFs with void connections of varying diameters, the selective separation of benzene and cyclohexane in both liquid and vapor phases is shown. The driving force of the highly efficient adsorption process is the formation of weak interactions between the adsorbed benzene molecules and the host framework.

Lanthanide contraction effect and white-emitting luminescence in a series of metal–organic frameworks based on 2,5-pyrazinedicarboxylic acid

A series of lanthanide and yttrium MOFs of two structural types [M₂(H₂O)₂(nmp)₂(pzc)₃] (1M) and [M₂(H₂O)₄(pzc)₃]·NMP·5H₂O (2M) (where M – lanthanide or yttrium cation, nmp – N-methyl-2-pyrrolidone, pzc²⁻ – 2,5-pyrazinedicarboxylate) was synthesized and characterized by single crystal and powder X-ray diffraction crystallography, TG, elemental analyses and IR-spectroscopy. The effect of lanthanide contraction has led to the fact that lanthanides at the beginning of the series (from lanthanum to gadolinium) have a structure different from the structure of lanthanides at the end of the series and yttrium (from terbium and beyond). According to PXRD patterns of the obtained samples mixed metal materials could be obtained not only as crystalline mixtures of two structure types but also as crystalline products of single structure type. Varying the ratio of lanthanides in the initial reaction mixture allowed us to obtain a wide color range of luminescence, including several near-white-light emitting samples.

Influence of the lanthanide contraction effect on the formation of a series of new MOFs and their wide colour range luminescence spectra.

Two novel organic phosphorous-based MOFs: synthesis, characterization and photocatalytic properties

Two novel coordination polymers were fabricated as efficient, stable, and reusable photocatalysts for the degradation of MB dye and the reduction of Cr(vi) aqueous solution.

CO2 capture in a carbazole-based supramolecular polyhedron structure: the significance of Cu(ii) open metal sites

Upon the removal of coordinated H₂O and DMF molecules to the paddlewheel of MOP 4 (followed by FTIR), it showed very interesting CO₂ capture properties at 196 K.

Confined methanol within InOF-1: CO2 capture enhancement

The CO₂ capture in InOF-1 was enhanced by confining small amounts of MeOH. DFT calculations coupled with forcefield based-MC simulations revealed that such an enhancement is due to an increase of the degree of confinement.

Confinement of alcohols to enhance CO2 capture in MIL-53(Al)

CO₂ capture of MIL-53(Al) was enhanced by confining small amounts of MeOH and i-PrOH within its micropores.

Aqua coordination to attenuate the luminescence properties of europium(iii)–phosphine oxide porous coordination polymers

Europium(iii)–phosphine oxide porous coordination polymers (Eu–PCPs) constructed from Eu(OTf)₃and tris(4-(4′-carboxylphenyl)phenyl)phosphine oxide as ligands are reported.

A two-dimensional flexible porous coordination polymer based on Co(ii) and terpyridyl phosphine oxide

A 2D framework with –P(O)Ph₂ phenyl groups on the layer surface has been obtained, which shows remarkable dynamic sorption behaviours.

Coordination polymers constructed from a tripodal phosphoryl carboxylate ligand: synthesis, structures and physical properties

Four coordination polymers based on a new tripodal phosphoryl carboxylate H₃TBPPO ligand have been constructed and characterized. Complexes 1–3 show 2-fold interpenetrating flu net, while complex 4 possesses a 4-fold interpenetrating dia network.

Porous anionic indium-organic framework with enhanced gas and vapor adsorption and separation ability

A three-dimensional microporous anionic metal-organic framework (MOF) (Et4N)3[In3(TATB)4] (FJI-C1, H3TATB=4,4',4''-s-triazine-2,4,6-triyltribenzoic acid) with large unit cell volume has been synthesized. Assisted by the organic cation group Et4N in the pores of the compound, FJI-C1 not only shows high adsorption uptakes of C2 and C3 hydrocarbons, but also exhibits highly selective separation of propane, acetylene, ethane, and ethylene from methane at room temperature. Furthermore, it also exhibits high separation selectivity for propane over C2 hydrocarbons and acetylene can be readily separated from their C2 hydrocarbons mixtures at low pressure due to the high selectivity for C2H2 in comparison to C2H4 and C2H6. In addition, FJI-C1 with hydrophilic internal pores surfaces shows highly efficient adsorption separation of polar molecules from nonpolar molecules. Notably, it exhibits high separation selectivity for benzene over cyclohexane due to the π-π interactions between benzene molecules and s-triazine rings of the porous MOF.