Sudip Mohapatra

Flexible and Rigid Amine-Functionalized Microporous Frameworks Based on Different Secondary Building Units: Supramolecular Isomerism, Selective CO2 Capture, and Catalysis

We report the synthesis, structural characterization, and porous properties of two isomeric supramolecular complexes of ([Cd(NH2 bdc)(bphz)0.5 ]⋅DMF⋅H2 O}n (NH2 bdc=2-aminobenzenedicarboxylic acid, bphz=1,2-bis(4-pyridylmethylene)hydrazine) composed of a mixed-ligand system. The first isomer, with a paddle-wheel-type Cd2 (COO)4 secondary building unit (SBU), is flexible in nature, whereas the other isomer has a rigid framework based on a μ-oxo-bridged Cd2 (μ-OCO)2 SBU. Both frameworks are two-fold interpenetrated and the pore surface is decorated with pendant -NH2 and NN functional groups. Both the frameworks are nonporous to N2 , revealed by the type II adsorption profiles. However, at 195 K, the first isomer shows an unusual double-step hysteretic CO2 adsorption profile, whereas the second isomer shows a typical type I CO2 profile. Moreover, at 195 K, both frameworks show excellent selectivity for CO2 among other gases (N2 , O2 , H2 , and Ar), which has been correlated to the specific interaction of CO2 with the -NH2 and NN functionalized pore surface. DFT calculations for the oxo-bridged isomer unveiled that the -NH2 group is the primary binding site for CO2 . The high heat of CO2 adsorption (ΔHads =37.7 kJ mol(-1) ) in the oxo-bridged isomer is realized by NH2 ⋅⋅⋅CO2 /aromatic π⋅⋅⋅CO2 and cooperative CO2 ⋅⋅⋅CO2 interactions. Further, postsynthetic modification of the -NH2 group into -NHCOCH3 in the second isomer leads to a reduced CO2 uptake with lower binding energy, which establishes the critical role of the -NH2 group for CO2 capture. The presence of basic -NH2 sites in the oxo-bridged isomer was further exploited for efficient catalytic activity in a Knoevenagel condensation reaction.

Guest‐Responsive Reversible Swelling and Enhanced Fluorescence in a Super‐Absorbent, Dynamic Microporous Polymer

A swell idea! The guest-responsive reversible swelling and fluorescence enhancement of a dynamic, microporous polymer network is presented. Guest-induced breathing of hydrophobic pores imparts multi-functional properties, such as super-absorbency, phase-selective swelling of oil from water and encapsulation of C(60) (see figure), to this soft micro-porous organic polymer.

Extended phenylene based microporous organic polymers with selective carbon dioxide adsorption

Two microporous conjugated polymers with extended phenylene backbones have been synthesized through Suzuki cross-coupling reactions. The structure and the pores of the polymers have been controlled by the use of para- and meta-structure directing 1,3,5-triphenyl tribromide monomers. Gas sorption studies revealed an unprecedented CO2 selectivity over N2 for these conjugated polymer networks. The networks have furthermore been tested as hydrogen storage materials and showed significant hydrogen uptake at high pressures.

Terbium(III), europium(III), and mixed terbium(III)-europium(III) mucicate frameworks: hydrophilicity and stoichiometry-dependent color tunability.

Two 3D porous terbium(III) mucicate frameworks, {[Tb(2)(Mu(2-))(3)(H(2)O)(2)]·4H(2)O}(n) (1) and {[Tb(Mu(2-))(Ox(2-))(0.5)(H(2)O)]·H(2)O}(n) (2), have been synthesized under hydrothermal conditions by changing the pH of the reaction medium. Isostructural europium(III) and seven mixed terbium(III)-europium(III) mucicates were synthesized by doping different percentages of Eu(III) under similar reaction conditions and unveiling different emission colors ranging from green to red under the same wavelength. Both dehydrated Tb(III) metal-organic frameworks exhibit selective H(2)O vapor sorption over other solvent molecules (MeOH, MeCN, and EtOH) of less polarity and bigger size and have been correlated to the highly hydrophilic pore surfaces decorated with -OH groups and O atoms from the carboxyl groups of mucicate.

Facile synthesis of anion dependent versatile CuI and mixed-valent porous CuI/CuII frameworks

CuX(2) (X = ClO(4)(-), NO(3)(-), 0.5 SO(4)(2-), Cl(-)) and 2,3-dihydroxyfumaric acid (dhfa) undergo redox reaction in slightly basic aqueous solution forming Cu(I)X and 2,3-diketosuccinic acid. Pyrazine (pyz) and 1,2-bis(4-pyridyl)ethylene (bpee) linkers have been used for stabilizing and isolating the Cu(I) state in this reaction. The three different Cu(I)-frameworks, {Cu(pyz)(1.5)(ClO(4))}(n) (1), {Cu(pyz)(NO(3))}(n) (2), and {[Cu(bpee)Cl].2H(2)O}(n) (3) with different anions have been synthesized and structurally characterized. The framework topology and dimensionality depends upon the anions. This is a one step synthesis of Cu(I) coordination frameworks with 1 : 2 stoichiometry in relation to dhfa and Cu(II). By controlling the concentration of dhfa, a mixed-valent porous Cu(I)/Cu(II) framework, [Cu(II)Cu(I)(2)(2,4-pyrdc)(2)(pyz)(3)].2H(2)O}(n) (4) has been synthesized and characterized by XPS and magnetic studies. Dehydrated frameworks of 3 and 4 exhibit interesting sorption properties with different solvent molecules. In a similar reaction CuCl(2) and pyz without dhfa produced the corresponding Cu(II)-compound, {Cu(pyz)Cl(2)}(n) (5), suggesting the reducing role of dhfa. Therefore by this simple reaction, it is possible to control the oxidation state as well as the coordination number and geometry of Cu ions. This is a novel synthetic methodology for the stabilization of the Cu +1 state in aqueous solution and open atmosphere.

A flexible supramolecular host with a crowned chair octameric water cluster and highly selective adsorption properties

A novel supramolecular host {[Fe(CN)6]·(H-bipy)3·8H2O} (1) was obtained by the reaction of K3[Fe(CN)6] and 4,4′-bipyridyl (bipy) under an acidic medium (pH ≈ 3). The supramolecular structure of 1 is made up of non-covalent forces viz. hydrogen bonding and π–π interactions. The host houses a discrete octameric water cluster with the conformation of a 1,4-substituted cyclohexane molecule where six water molecules are positioned on the vertices of the cyclohexane ring and the seventh and eighth occupy the 1,4-equatorial positions of the ring. DFT calculations suggest that this conformation is more stable (−73.08 kcal mol−1) when compared to the a,a conformation. Upon removal of the water molecules, the host network of 1 undergoes a structural transformation and the dehydrated phase exhibits a stepwise uptake of H2O vapour and completely excludes CO2 and other organic solvent molecules (CH3OH, CH3CN and EtOH).

Two 3D supramolecular frameworks assembled from the dinuclear building block: A crystallographic evidence of carboxylate(O)…π interaction

AbstractFigure. In two new complexes of Mn(II) and Zn(II), it has been observed that carboxylate (O)…π interactions played a crucial role in the organization of supramolecular structure and that carboxylate (O)…π interactions also somehow controlled by the C-H…π interactions, which is achieved by proper modulation of the linkers. Graphical AbstractIn two new complexes of Mn(II) and Zn(II), it has been observed that carboxylate (O)…π interactions played a crucial role in the organization of supramolecular structure and that carboxylate (O)…π interactions also somehow controlled by the C-H…π interactions, which is achieved by proper modulation of the linkers.