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Title: Silicon-containing COFs and MOFs for CO2 capture
Author: Bull, Okpara Sergeant
ISNI:       0000 0004 9356 6803
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2018
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This work was conducted in order to explore the potential of novel silicon-based Covalent Organic Frameworks (COFs) and Metal-Organic Frameworks (MOFs) for CO2 capture. A Lewis acid, cyclo-1,3,3,5,7,7-hexaphenyl-1,5-dibora-3,7-disiloxane (3) was synthesized and complexed with a variety of Lewis bases such as 4,4ˈbipyridine (L1), 1,2-di(pyridin-4- yl)ethane (L2), 1,2-di(pyridin-4-yl)ethene (L3), 1,3-di(pyridin-4-yl)propane (L4), 1,2- di(pyridin-4-yl)sulfane (L5), 1,2-di(pyridin-4-yl)diazene (L6), 1,4-di(pyridin-4-yl)benzene (L7), 3,5-di(pyridin-3-yl)-1,2,4-thiadiazole (L8) and 3,5-di(pyridin-4-yl)-1,2,4-thiadiazole (L9) to afford a range of 1-D polymers such as as [Ph6B2Si2O4].L1 (4), [Ph6B2Si2O4].L2 (5), [Ph6B2Si2O4].L3 0.5(CH2Cl2) (6), [Ph6B2Si2O4].L4 (7), [Ph6B2Si2O4].L5 (8), [Ph6B2Si2O4].2L9. 2[PhB(OH)2] (14) as well as a short polymeric structure [Ph6B2Si2O4].L8 (13). In addition, other compounds such as Ph8B4Si2O6.L6 (9), 4(C12H12O2Si).3(C10H8N4) (10), Ph4Si2(OH)4.2L7 (11) and Ph8B4Si2O6.L7 (12) were formed due to ring contraction readiness of compound (3). These compounds displayed extended inter- and intra-molecular π-π and other forms of π-interactions as well as hydrogen bonding in their crystal packings. Furthermore, novel silicon-based tetrakis-, tris- and di- aryl-pyridine linkers such as tetrakis(4-(pyridine-4-vinyl)phenyl)silane (L10), tri(4-(pyridine-4-vinyl)phenyl)methylsilane (L11), bis(4-(pyridine-4- vinyl)phenyl)dimethylsilane (L12) tetrakis(4-(pyridine-4-vinyl)biphenyl)silane L13), tri(4- (pyridine-4-vinyl)biphenyl)methylsilane (L14), as well as aryl-carboxylic acid linkers such as silane tetrakis(biphenyl-4-carboxylic acid) (L15) and silane tris(biphenyl-4-carboxylic acid) (L16) have been synthesized from their corresponding aryl-bromine precursors. Treatment of (L10) with Zn(CH3COO)2 and Zn(NO3)2.6H2O give a 2-D (MOF) (17) and a 3-D MOF (18) respectively. While (L15) solvothermally formed MOF (19) after treatment with Zn(NO3)2.6H2O in solvent mixture of H2O/DMA. MOF (17) possesses a pore size of 18.5 Å iv with no interpenetration of channels while (18) exhibits a five-fold interpenetration of channels as well as two types of pores with length and width of 31.42 and 24.62 Å for the big pores and 15.70 and 12.20 Å for the small pores respectively. MOF (19) exhibits a pore diameter of 17.06 Å.
Supervisor: Lickiss, Paul ; Davies, Rob Sponsor: Government of Nigeria
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral