| 1. |
- Gumbo, Maureen, et al.
(author)
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A single site catalyst supported in mesoporous UiO-66 for catalytic conversion of carbon dioxide to formate
- 2024
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In: Sustainable Energy and Fuels. - 2398-4902. ; 8:4, s. 777-788
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Journal article (peer-reviewed)abstract
- Carbon dioxide utilisation strategies are of paramount importance, yielding various products such as methanol and formate. Formate is an excellent hydrogen carrier in fuel cells, making it a highly exploitable chemical on the hydrogen energy storage front. Formate has an energy content that is at least five times greater than that of commercially available lithium-ion batteries. Herein, we have prepared mesoporous metal-organic frameworks (MOFs) (m-UiO-66 and m-UiO-66-NH2), using a Zr-based secondary building unit (SBU) and terephthalate linkers. The MOFs were used to support the half-sandwich (tetrazolylpyridyl)iridium(iii) complex to make single-site catalyst (Ir(iii)@m-UiO-66 and Ir(iii)@m-UiO-66-NH2) for CO2 conversion to formate. Both Ir(iii)@m-UiO-66 and Ir(iii)@m-UiO-66-NH2 exhibited improved activity for CO2 hydrogenation to formate in a heterogeneous system. Ir(iii)@m-UiO-66-NH2 and Ir(iii)@m-UiO-66 had turnover numbers of 3313 and 3076 TON, respectively, under optimized conditions. X-ray photoelectron spectroscopy (XPS) showed possible interaction of the complex with the MOF as evidenced by a downfield shift in the binding energies of the Ir 4f electronic environment. The catalysts showed post-catalysis stability, as confirmed by PXRD, FTIR, and XPS. The Ir 4f binding energies of the materials after catalysis showed an up-field shift confirming the presence of Ir-H species which are the active species for catalysis.
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| 2. |
- Makhubela, B. C. E., et al.
(author)
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Hydroformylation of 1-octene using low-generation Rh(I) metallodendritic catalysts based on a tris-2-(2-pyridyliminoethyl)amine scaffold
- 2012
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In: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 41:35, s. 10715-10723
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Journal article (peer-reviewed)abstract
- The synthesis and characterization of low-generation pyridylimine Rh(I) metallodendrimers is described. These metallodendrimers were obtained via a Schiff base condensation of tris-2-(aminoethyl) amine with 2-pyridinecarboxaldehyde to afford the tris-2-(2-pyridylimine ethyl) amine ligand (1). Subsequent complexation reactions with [RhCl(CO)(2)](2) and [RhCl(COD)](2) yielded the corresponding metal-containing dendrimers containing RhCl(CO) and Rh(COD) moieties on the periphery. These new rhodium metallodendrimers (2 and 3) and their precursor ligand (1) are thermally stable and have been characterized using H-1 NMR, C-13 NMR, P-31 NMR, FT-IR spectroscopy, elemental analysis as well as mass spectrometry. The Rh(I) metallodendrimers are highly active and chemo- and regioselective in the hydroformylation of 1-octene. Aldehydes were favoured at moderate to high temperatures (95 degrees C and 75 degrees C) and pressure (30 bars), while more iso-octenes were formed at low temperature (55 degrees C) and pressures (5 and 10 bars). The mononuclear analogues (5 and 6) also produced more aldehydes (albeit showing catalyst decomposition at 95 degrees C and 75 degrees C, 30 bars) and these aldehydes were mostly branched.
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| 3. |
- Tshuma, Piwai, et al.
(author)
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Cyclometalation of lanthanum(iii) based MOF for catalytic hydrogenation of carbon dioxide to formate
- 2020
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In: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 10:6, s. 3593-3605
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Journal article (peer-reviewed)abstract
- The hydrogenation of carbon dioxide (CO2) to formic acid is of great importance due to its useful properties in the chemical industry. In this work, we have prepared a novel metal-organic framework (MOF), JMS-1, using bipyridyl dicarboxylate linkers, with molecular formula [La2(bpdc)3(DMF)3]n. Network analysis of JMS-1 revealed a new 7-connected topology (zaz). The MOF backbone of the activated phase (JMS-1a) was functionalized by cyclometalation using [RuCl2(p-cymene)]2 to produce Ru(ii)@JMS-1a. Both JMS-1a and Ru(ii)@JMS-1a were able to convert CO2 in the presence of hydrogen to formate. Ru(ii)@JMS-1a displayed outstanding conversion evidenced by a yield of 98% of formate under optimized conditions of total pressure 50 bar (CO2/H2 = 1 : 4, temperature 110 °C, time 24 h, 5 mmol KOH, 8 mL ethanol). This work is significant in providing new strategies of incorporating active catalytic centres in MOFs for efficient and selective conversion of CO2 to formate.
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