Synthesis, Structures, and CO2 Capture of Amide-Containing Metal?{Organic Frameworks

• Main Authors: Cheng-Hua Lee, 李政樺
• Other Authors: Lu, Kuang-Lieh
• Format: Others
• Language: en_US
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/94913641441011132174

博士 === 國立臺灣科技大學 === 應用科技研究所 === 101 === In this thesis, a series of amide-containing metal?{organic frameworks (MOFs) was synthesized by reacting amide-containing pyridyl ligands, various carboxylate ligands and transition metal salts in H2O/DMF solution under solvothermal conditions. The eleven compounds that were prepared are comprised of one dimensional zigzag-chains, two dimensional and three dimensional structures. The structures of the compounds {[Zn4(bdc)4(bpda)4]•5DMF• 3H2O}n (1)、{[Mn2(2,6-ndc)2(bpda)2]•5DMF}n (3)、{[Zn2(thdc)2(bpda)2(DMF)]• 1.5DMF}n (5) and {[Co2(thdc)2(bpda)2(DMF)]• 1.5DMF}n (6) could be simplified as ??Po 412•63 networks and compounds {[Zn2(1,3-bdc)2(bpda)2]•3DMF•0.5H2O}n (7)、[Zn(1,4-ndc)0.5(bpda)(dmc)]n (8) and [Zn(2,6-pdc)(bpda)]n (10) display common 44-sql and (6,3)-connected networks. Compound {[Cd3(4-btapa)2(2,6-ndc)3]•9H2O}n (2) and {[Co3(btc)2(bpda)3]•5H2O}n (4) exhibit (63)2(614•8)3 and (63)2(64•8•10)3 networks, which are rare topological structures. Compounds 1?{3, 7, 8 and 11 are porous materials, in which the unsheltered amide groups are located found in the channels. In the open-ended channels of compounds 1 and 3, the unsheltered amide groups exhibit a unique spatial arrangement, which confers a positive cooperative effect for the compounds for the adsorption of CO2 molecules, as shown by the significant increase in the CO2 adsorption enthalpy with increasing CO2 uptake. In addition, compound 1 shows a 1:1 ratio of active amide sites to CO2 molecules at ambient condition. It is noteworthy that compound 3 exhibits a rare CO2 gate-opening adsorption behavior, in which compound 3 has a striking selectivity for CO2 over N2. Compound 2 is an unusual three-fold self-penetrating 3D framework. In the structure, the amide groups of the coordinated 4-btapa ligands are arranged in a unique multi-function envirnment in the structure, which act as superior adsorbing sites for capturing CO2 molecules. Importantly, the isosteric heat of CO2 adsorption (Qst) for compound 2 is the highest physical sorption value reported to date for amide-containing functionalized MOFs. The amount of CO2 uptake with lower isosteric heat for compounds 7 and 8 can be attributed to the fact that the amide groups in the two dimensional structures are unable to provide a positive cooperative effect on the adsorption of CO2 molecules. Although, compound 11 possesses the highest porosity (57% free space) among the above-mentioned compounds. It is not an ideal candidate for CO2 adsorption due to fact that the structure collapses after the removal of the guest mulecules. Compounds 5, 7 and 11 exhibit an emission at 410~480 nm, which is similar to that for bpda and 4-tpaba ligands. The emission spectra of compounds 9 and 10 have an observable red-shift as compared with the ligands, which may be assigned to the existence of intraligand and ligand-to-ligand charge transfer (LLCT) transions.