Kaige ShiFollow

Document Type

Thesis

Degree

Doctor of Philosophy (PhD)

Major/Program

Chemistry

First Advisor's Name

Raphael G Raptis

First Advisor's Committee Title

Committee Chair

Second Advisor's Name

Konstantinos Kavallieratos

Second Advisor's Committee Title

Committee member

Third Advisor's Name

Yuk-Ching Tse-Dinh

Third Advisor's Committee Title

committee member

Fourth Advisor's Name

Jaroslava Miksovska

Fourth Advisor's Committee Title

committee member

Fifth Advisor's Name

Chunlei (Peggy) Wang

Fifth Advisor's Committee Title

committee member

Keywords

copper pyrazolate complexes, electrochemistry, MOFs, Gas adsorption

Date of Defense

6-12-2018

Abstract

The main objectives of this project are the synthesis and redox- or photo-active modification and CO2 adsorption studies of metal-organic frameworks (MOFs) based on Cu3-pyrazolate secondary building units (SBUs). Trinuclear copper(II) complexes of the formula [Cu3(µ3-O)(µ-4-R-pz)3X3]z have been studied extensively due to their redox, magnetic and catalytic properties. In earlier work, we have shown that trinuclear copper(II) complexes of the formula [Cu3(µ3-O)(µ-4-R-pz)3X3]z pz = pyrazolato anion; R = H, CH(O), Cl, Br and NO2; X = Cl, NCS, CH3COO, CF3COO and pyridine – can be oxidized to the corresponding z+1, formally CuII2CuIII, species. In this project, fourteen (14) new copper-pyrazolate complexes of varying nuclearities (Cu3, Cu6, Cu7 and Cu12), terminal ligands (-NO2, py, -N3, -Cl) and bridging ligands (4-Cl-pzH and 4-Ph-pzH) have been synthesized. Efforts have been made to prepare MOFs based on the Cu3(µ3-O)-SBUs. While attempting to design the most suitable SBU for redox-active MOF construction, it was found that the one-electron oxidation of the all-CuII complex [Cu3(µ3-O)(µ-pz)3(NO2)3]2–, [8]2-, was achieved at redox potential more cathodic than any other Cu3(µ3-O)-complexes studied in our laboratory. The mixed-valent compound, [Cu3(µ3-O)(µ-pz)3(NO2)3]–, [8]-, the easiest accessible CuII2CuIII species known to date, was characterized spectroscopically. Compound [8] and analogous [11] release NO almost quantitatively upon the addition of PhSH or acetic acid. The system is catalytic in the presence of excess nitrite.

Before embarking on the study of photo-active MOFs, a simpler model compound – a dimer of trimer [{Cu3(µ3-OH)(µ-4-Cl-pz)3(py)2}2(µ-abp)](ClO4)4 [21], where abp = 4,4’-azopyridine, was synthesized and its photochemistry was studied. The absorption spectra recorded before and after irradiation indicated a structural change. Two dimensional (2D) and three dimensional (3D) materials with {[Cu3(µ3-OH)(µ-4-R-pz)3]2+}n SBUs where R = Ph or Cl , which can potentially undergo cis/trans-isomerization, have been prepared during this project. A Phenyl substituent at 4-position on the pyrazole ligand leads to the formation of new class of 2D sheets. Three new 3D porous MOFs based on {[Cu3(µ3-OH)(µ-4-Cl-pz)3]2+}n SBUs have interpenetrated- lattice structures and are capable of adsorbing CO2 selectively. Compounds FIU-1 and FIU-3 also exhibit hysteretic sorption-desorption profiles indicating the flexibility of the MOFs upon adsorption. Compound FIU-1 demonstrates the usefulness of a hexanuclear CuII -pyrazolate moiety as an SBU for generating 3-fold interpenetrated 3D polymeric network. Complexes FIU-2 and FIU-3 have novel 3-fold interpenetrating 3D hexagonal framework structures. Compound FIU-2 crystallizes in the monoclinic crystal system with the P21/c space group, whereas FIU-3 crystallizes in triclinic space group P . Both structures contain Cu3-SBUs connected by the linkers through the Cu-termini.

Identifier

FIDC007044

ORCID

https://orcid.org/0000-0002-4341-3919

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