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Kurisingal, Jintu Francis,Babu, Robin,Kim, Seol-Hee,Li, Yi Xin,Chang, Jong-San,Cho, Sung June,Park, Dae-Won The Royal Society of Chemistry 2018 Catalysis Science & Technology Vol.8 No.2
<P>The aqueous synthesis of a bimetallic metal organic framework (MOF) with Ni and Co as the active metal centers and benzene-1,4-dicarboxylic acid as the linker has been achieved rapidly in high yield using microwave irradiation. The synthesized MOF is investigated for its catalytic efficacy in the synthesis of cyclic carbonates from epoxides and CO2. The Ni-Co-MOF provides high conversion rates of epoxides to cyclic carbonates with >99% selectivity under solvent-free conditions. The bimetallic framework (Ni-Co-MOF) exhibits superior catalytic activity to those of the corresponding single metal MOF catalysts (Ni-MOF and Co-MOF) and their mechanical combination (Ni-MOF + Co-MOF), which indicates the existence of a synergistic catalytic effect based on charge transfer between the Ni and Co metal centers and is highly advantageous for the catalytic chemical fixation of CO2. The catalytic potential of the Ni-Co-MOF is also applied to terminal and cyclic epoxides, and a recyclability study over a minimum of six cycles is also conducted. Finally, a plausible reaction mechanism for Ni-Co-MOF-catalyzed epoxide-CO2 cycloaddition reactions is also proposed.</P>
최각규,Jintu Francis Kurisingal,CHUNG YONGCHUL GREGO,박대원 한국화학공학회 2018 Korean Journal of Chemical Engineering Vol.35 No.6
A two-dimensional Zn-based metal-organic framework has been synthesized by using Zn(II) ions and H2SDC (4,4'-stilbenedicarboxylic acid) under solvothermal conditions. The framework having a trinuclear Zn3-(RCO2)6 SBUs connected by the 4,4'-stilbenedicarboxylic acid to form a hexagonal network, shows a two-dimensional structure and displays high thermal stability up to approximately 330 oC. The role of Zn2+ (from Zn-SDC) for epoxide activation and Br- ion (from TBABr) for ring opening of epoxide was studied for the cycloaddition reaction of CO2 and propylene oxide (PO) under ambient conditions. Zn-SDC was found catalytically efficient towards CO2-epoxide coupling under ambient reaction conditions with high selectivity towards the desired cyclic carbonates under solvent-free conditions. The effects of various reaction parameters such as catalyst loading, temperature, CO2 pressure, and time were evaluated. Zn-SDC was easily separable and reusable at least five times without any considerable loss in the initial activity. A plausible reaction mechanism for the cycloaddition reaction was also proposed based on literature and experimental inferences.
Babu, Robin,Kurisingal, Jintu Francis,Chang, Jong-San,Park, Dae-Won WILEY-VCH 2018 CHEM SUS CHEM Vol.11 No.5
<P>A pyridinium-based ionic-liquid-decorated 1D metal-organic framework (MOF; IL-[In-2(dpa)(3)(1,10-phen)(2)]; IL = ionic liquid; dpa = diphenic acid; 1,10-phen = 1,10-phenanthroline) was developed as a bifunctional heterogeneous catalyst system for CO2-oxirane coupling reactions. An aqueous-microwave route was employed to perform the hydrothermal reaction for the synthesis of the [In-2(dpa)(3)(1,10-phen)(2)] MOF, and the IL-[In-2(dpa)(3)(1,10-phen)(2)] catalyst was synthesized by covalent postfunctionalization. As a result of the synergetic effect of the dual-functional sites, which include Lewis acid sites (coordinatively unsaturated In sites) and the I- ion in the IL functional sites, IL-[In-2(dpa)(3)(1,10-phen)(2)] displayed a high catalytic activity for CO2-epoxide cycloaddition reactions under mild and solvent-free conditions. Microwave pulses were employed for the first time in MOF-catalyzed CO2-epoxide cycloaddition reactions to result in a high turnover frequency of 2000-3100 h(-1). The catalyst had an excellent reusability and maintained a continuous high selectivity. Furthermore, only a small amount of leaching was observed from the spent catalyst. A plausible reaction mechanism based on the synergistic effect of the dual-functional sites that catalyze the CO2-epoxide cycloaddition reaction effectively is proposed.</P>
Rachuri, Yadagiri,Kurisingal, Jintu Francis,Chitumalla, Ramesh Kumar,Vuppala, Srimai,Gu, Yunjang,Jang, Joonkyung,Choe, Youngson,Suresh, Eringathodi,Park, Dae-Won American Chemical Society 2019 Inorganic Chemistry Vol.58 No.17
<P>We synthesized two new adenine-based Zn(II)/Cd(II) metal-organic frameworks (MOFs), namely, [Zn<SUB>2</SUB>(H<SUB>2</SUB>O)(stdb)<SUB>2</SUB>(5H-Ade)(9H-Ade)<SUB>2</SUB>]<SUB><I>n</I></SUB> (PNU-21) and [Cd<SUB>2</SUB>(Hstdb)(stdb)(8H-Ade)(Ade)]<SUB><I>n</I></SUB> (PNU-22), containing auxiliary dicarboxylate ligand (stdb = 4,4′-stilbenedicarboxylate). Both MOFs were characterized by multiple analytical techniques such as single-crystal X-ray diffraction (SXRD), powder X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, thermogravimetric analysis, scanning electron microscopy, as well as temperature program desorption and Brunauer-Emmett-Teller measurements. Both MOFs were structurally robust and possessed unsaturated Lewis acidic metal centers [Zn(II) and Cd(II)] and free basic N atoms of adenine molecules. They were used as heterogeneous catalysts for the fixation of CO<SUB>2</SUB> into five-membered cyclic carbonates. Significant conversion of epichlorohydrin (ECH) was attained at a low CO<SUB>2</SUB> pressure (0.4 MPa) and moderate catalyst (0.6 mol %)/cocatalyst (0.3 mol %) amounts, with over 99% selectivity toward the ECH carbonate. They showed comparable or even higher catalytic activity than other previously reported MOFs. Because of high thermal stability and robust architecture of PNU-21/PNU-22, both catalysts could be reused with simple separation up to five successive cycles without any considerable loss of their catalytic activity. Densely populated acidic and basic sites in both Zn(II)/Cd(II) MOFs facilitated the conversion of ECH to ECH carbonate in high yields. The reaction mechanism of the cycloaddition reaction between ECH and CO<SUB>2</SUB> is described by possible intermediates, transition states, and pathways, from the density functional theory calculation in correlation with the SXRD structure of PNU-21.</P><P>Adenine-based two Zn(II)/Cd(II) metal−organic frameworks were synthesized and characterized by various analytical techniques including SXRD. Both MOFs were utilized as potential catalysts for the syntheses of cyclic carbonates from CO<SUB>2</SUB> and epoxides. The mechanistic aspects of cycloaddition reaction of CO<SUB>2</SUB> and ECH were studied systematically by DFT.</P> [FIG OMISSION]</BR>
Babu, Robin,Roshan, Roshith,Gim, Yeongrok,Jang, Yun Hee,Kurisingal, Jintu Francis,Kim, Dong Woo,Park, Dae-Won The Royal Society of Chemistry 2017 Journal of materials chemistry. A, Materials for e Vol.5 No.30
<P>The correlation between dimensionality and active sites on deciding the catalytic performance of an MOF catalyst in CO2-epoxide cycloaddition reactions has been studied. Seven In(iii) based MOFs built from carboxylic and N-donor ligands possessing different dimensionalities and distinct coordination environments were chosen as solid acid catalysts for this study. The origin of the catalytic activity of an In<SUP>3+</SUP>/TBAB bifunctional system in a CO2-PO reaction was studied in detail by performing density functional theory (DFT) calculations at the M06/LACVP**++ level. The energy barrier of the propylene oxide ring opening in the presence of In<SUP>3+</SUP>/Br<SUP>−</SUP>is 11.5 kcal mol<SUP>−1</SUP>, which is significantly lower than those of un-catalyzed (55-63 kcal mol<SUP>−1</SUP>) and Br<SUP>−</SUP>-catalyzed (19.5 kcal mol<SUP>−1</SUP>) reactions, which confirms the importance of the In<SUP>3+</SUP>/Br<SUP>−</SUP>binary catalytic system in the CO2-epoxide cycloaddition reactions. The one-dimensional (1D) MOF with unsaturated metal centers exhibited higher catalytic activity (PO conversion: 91%, temperature: 50 °C, and time: 12 h) than the two- and three-dimensional MOFs. The roles of dimensionality and unsaturated metal centers in cycloaddition reactions were explained on the basis of the results of activity testing and structural investigations. In addition, a plausible reaction mechanism for the catalytic activity of the 1D MOF was proposed with reference to our structure-density functional theory correlations.</P>