Junfeng Bai

Enhanced CO2 Binding Affinity of a High-Uptake rht-Type Metal−Organic Framework Decorated with Acylamide Groups

An rht-type metal-organic framework (MOF) prepared from M(2)(carboxylate)(4) (M = Cu, Co) paddlewheel clusters and a flexible C(3)-symmetric hexacarboxylate ligand with acylamide groups exhibits larger CO(2) uptake, an enhanced heat of adsorption, and higher selectivity toward CO(2)/N(2) in comparison with what was previously observed for an analogous MOF with alkyne groups.

Temperature controlled reversible change of the coordination modes of the highly symmetrical multitopic ligand to construct coordination assemblies: experimental and theoretical studies.

By fine-tuning the reaction temperature to 5, 15, 30, and 50 degrees C, respectively, four different complexes, [Cd(HC4O4)2(H2O)4] (1), [Cd4(C4O4)4(H2O)16].(H2O)2 (2), [Cd(C4O4)(H2O)2] (3), and [Cd(C4O4)(H2O)2] (4), were formed successfully from the identical initial reaction mixture. Moreover, an unprecedented reversible interconversion among the four complexes at the corresponding reaction temperatures mediated by the mother liquor was observed.

Fine-Tuning Pore Size by Shifting Coordination Sites of Ligands and Surface Polarization of Metal–Organic Frameworks To Sharply Enhance the Selectivity for CO2

Based upon the (3,6)-connected metal-organic framework {Cu(L1)·2H(2)O·1.5DMF}(∞) (L1 = 5-(pyridin-4-yl)isophthalic acid) (SYSU, for Sun Yat-Sen University), iso-reticular {Cu(L2)·DMF}(∞) (L2 = 5-(pyridin-3-yl)isophthalic acid) (NJU-Bai7; NJU-Bai for Nanjing University Bai group) and {Cu(L3)·DMF·H(2)O}(∞) (L3 = 5-(pyrimidin-5-yl)isophthalic acid) (NJU-Bai8) were designed by shifting the coordination sites of ligands to fine-tune pore size and polarizing the inner surface with uncoordinated nitrogen atoms, respectively, with almost no changes in surface area or porosity. Compared with those of the prototype SYSU, both the adsorption enthalpy and selectivity of CO(2) for NJU-Bai7 and NJU-Bai8 have been greatly enhanced, which makes NJU-Bai7 and NJU-Bai8 good candidates for postcombustion CO(2) capture. Notably, the CO(2) adsorption enthalpy of NJU-Bai7 is the highest reported so far among the MOFs without any polarizing functional groups or open metal sites. Meanwhile, NJU-Bai8 exhibits high uptake of CO(2) and good CO(2)/CH(4) selectivity at high pressure, which are quite valuable characteristics in the purification of natural gases.

Unprecedented interweaving of single-helical and unequal double-helical chains into chiral metal–organic open frameworks with multiwalled tubular structures

Two novel chiral metal-organic open frameworks with unprecedented multiwalled tubular channels and interweaving of single-helical and unequal double-helical units were reported, which possess novel four-connected 4(2)8(3)10 topology and represent the first examples of functional metal-organic frameworks based on both flexible tripodal and flexible bisdentate ligands.

Pentaphosphaferrocene as a Linking Unit for the Formation of One‐ and Two‐Dimensional Polymers

Different copper halide, different copper product: The cyclo-P5-ligand complex [Cp*Fe(5-P5)] (1; Cp*=C5Me5) reacts with CuBr and CuI to give two-dimensional networks in which 1 is the linking unit. However, a novel one-dimensional-chain coordination polymer (see picture) is formed with CuCl.

Synthesis, structures and properties of nickel(II) and cobalt(II) metal–organic frameworks based on a flexible tricarboxylate ligand H3TTG and different pyridyl-containing ligands

Along with our recent investigations on Ni and Co coordination frameworks of a flexible tripodal ligand of H3TTG (N,N′,N″-1,3,5-triazine-2,4,6-triyltris-glycine), four new complexes {[Ni(HTTG)(4,4′-bpy)(H2O)3]·(H2O)2}n (1), {[Ni2(HTTG)2(bpe)2(H2O)]·(H2O)6}n (2), {[Co2(HTTG)2(bpe)2(H2O)]·(H2O)6}n (3) and {[Co3(TTG)2(bpe)2]·(H2O)2}n (4) were hydrothermally synthesized through reactions of this ligand with different pyridyl-containing ligands {4,4′-bpy (4,4-bipyridine), bpe [1,2-bi(4-pyridyl)ethane]}, respectively. Due to various coordination modes and conformations of the flexible tricarboxylate ligand and pyridyl-containing coligands, these complexes exhibit structural and dimensional diversity. Complex 1 shows a unique 1D chain bridged by the R22(8) hydrogen bonds between the carboxylate groups, the triazine rings, and hydrogen-bonded networks of the solvent water molecules as well. Complexes 2 and 3 are isomorphous and both exhibit special 2D (8,2)-connected double-layer structures with two kinds of 1D channels constructed by the coordination bonds and hydrogen bonding interactions, respectively. Complex 4 features a 3-D network with scarce (8,3)-connected rutile-related topology with a Schlafli symbol (42,622,7,83)(4,62)2 based on secondary building units (SBUs) of linear cobalt clusters [Co3(CO2)4]2−. Significantly, with increasing flexibility of the pyridyl-containing coligands, these corresponding complexes become more and more complicated. In addition, their physical properties such as thermal, XPRD, and magnetism have also been investigated.

Pentaphosphaferrocen als verknüpfende Einheit in ein‐ und zweidimensionalen Polymeren

Unterschiedliche Produkte mit unterschiedlichen Kupferhalogeniden: Der cyclo-P5-Ligandkomplex [Cp*Fe(5-P5)] 1 bildet bei der Reaktion mit CuBr und CuI zweidimensionale Netzwerke mit 1 als verknupfender Einheit, wahrend mit CuCl ein Koordinationspolymer mit eindimensionaler Kettenstruktur entsteht (siehe Bild).

Structures and Properties of Spherical 90-Vertex Fullerene-Like Nanoballs

By applying the proper stoichiometry of 1:2 to [Cp(R)Fe(eta(5)-P(5))] and CuX (X=Cl, Br) and dilution conditions in mixtures of CH(3)CN and solvents like CH(2)Cl(2), 1,2-Cl(2)C(6)H(4), toluene, and THF, nine spherical giant molecules having the simplified general formula [Cp(R)Fe(eta(5)-P(5))]@[{Cp(R)Fe(eta(5)-P(5))}(12){CuX}(25)(CH(3)CN)(10)] (Cp(R)=eta(5)-C(5)Me(5) (Cp*); eta(5)-C(5)Me(4)Et (Cp(Et)); X=Cl, Br) have been synthesized and structurally characterized. The products consist of 90-vertex frameworks consisting of non-carbon atoms and forming fullerene-like structural motifs. Besides the mostly neutral products, some charged derivatives have been isolated. These spherical giant molecules show an outer diameter of 2.24 (X=Cl) to 2.26 nm (X=Br) and have inner cavities of 1.28 (X=Cl) and 1.20 nm (X=Br) in size. In most instances the inner voids of these nanoballs encapsulate one molecule of [Cp*Fe(eta(5)-P(5))], which reveals preferred orientations of pi-pi stacking between the cyclo-P(5) rings of the guest and those of the host molecules. Moreover, pi-pi and sigma-pi interactions are also found in the packing motifs of the balls in the crystal lattice. Electrochemical investigations of these soluble molecules reveal one irreversible multi-electron oxidation at E(p)=0.615 V and two reduction steps (-1.10 and -2.0 V), the first of which corresponds to about 12 electrons. Density functional calculations reveal that during oxidation and reduction the electrons are withdrawn or added to the surface of the spherical nanomolecules, and no Cu(2+) species are involved.

P2-Ligand Complexes as Building Blocks for the Formation of One-Dimensional Polymers

Bridging coordination of Mo2P2 complexes between metal centers is a prerequisite for the formation of a one-dimensional polymer. The choice of counterion also has a deciding role in determining the polymer structure: while the complex [Cp2Mo2(CO)4(,2-P2)] (1; Cp=C5H5) with AgNO3 forms a zigzag polymer chain, with CuBr 1 forms a linear coordination polymer (see structure).

Porous NbO-type metal–organic framework with inserted acylamide groups exhibiting highly selective CO2 capture

A new expanded microporous NbO-type metal–organic framework [Cu2(BDPT4−)]n with inserted acylamide groups has been designed and synthesized, which shows both a large CO2-uptake capacity (156.4 cm3 g−1 at 1 bar) and a high selectivity for CO2 over N2 (39.8) and CH4 (7.2) at 273 K.