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Title: Development of Bismuth and Lead Based Coordination Polymers/Metal-Organic Frameworks
Authors: Iram, Shamaila
Keywords: Chemistry
Issue Date: 2019
Publisher: University of Sindh, Jamshoro.
Abstract: Bismuth and lead based MOFs (1–21) have been synthesized by using eight different organic linkers. For better understanding and comparison of structural and bonding aspects, these linkers were divided into four categories (A–D). This categorization was made on the basis of functional molecules present in them. Category A include linkers having only dicarboxylate groups i.e., (biphenyl-4,4′-dicarboxylic acid (H2BDA), 2,6-naphthalenedicarboxylic acid (2,6-NDA), 2,5-thiophenedicarboxylic acid (H2TDC), 2-bromoterephthalic acid (H2-BTA)), Category B include linker having dicarboxylate and hydroxyl groups i.e., (5-hydroxyisophthalic acid (H2HIA)), Category C include linkers having monocarboxylate and thione groups i.e., (2-mercapto-3-methyl-4 thiazoleacetic acid (H2MMTA), 4-mercaptobenzoic acid (H2MBA)) and Category D include linker having thione and hydroxyl groups i.e., (4,6-dihydroxy-2-mercapto pyrimidine (H2-DMP)). MOFs (1–9) were synthesized from A linkers, MOFs (10–12) were synthesized from B linker. Similarly MOFs (13–18) were synthesized from C linkers and MOFs (19–21) were synthesized from D linker. The morphological and other structural aspects of all these MOFs (1–21) have been established on the basis of Fourier transform infrared spectroscopy (FTIR), 1H NMR, Scanning electron microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDS), Thermogravimetric analysis (TGA), Powder X-ray diffraction techniques and in case of MOF (13) single-crystal X-ray diffraction have been used. MOF (13) exhibited orthorhombic crystal system in which central lead metal ions form a chain which is bridged to other chains through H2MMT linker to form a 3D framework. The octahedron around each lead was hemidirected. Powder XRD revealed orthorhombic system for MOFs (2, 4–13, 15 & 18–21), trigonal xx crystal system for MOF (3), hexagonal crystal system for MOF (12) and monoclinic crystal system for MOFs (16 & 17). Thermogravimetric analysis was carried out to investigate the thermal stability of all MOFs (1–21). It was observed that all bismuth MOFs (3, 5, 15 & 18) are relatively more stable than lead based MOFs (1–4, 6–11, 13, 14, 16, 17–20). All these MOFs exhibited appreciable to good luminescence activity. Lead-based MOFs exhibited better emission at 527 nm, 499 nm and 514 nm among all other MOFs. Adsorption behavior is a key focus in MOFs application. Hence BET studies for MOFs (1–21) were investigated to estimate the surface area that is in the range 196-5316 m2/g. Among these MOFs, highest surface area was found to be 3699 m2/g for (6), 2866.5 m2/g for (10), 3266.5 m2/g for (11), 5130 m2/g for (14), 5316 m2/g for (15), 2184m2/g for (18) and 3477 m2/g for (21) and showed appreciable to good adsorption capacity (17.62 mmol/g (6), 11.12 mmol/g (10), 6.23 mmol/g (11),9.12 mmol/g (14), 11.90 mmol/g (15), 1.84 mmol/g (18) and 13.66 mmol/g (21)) for N2. Bismuth is surprisingly less toxic relative to its neighboring elements (Pb & Tl). Therefore we have also investigated antibacterial activity of bismuth MOFs against three Gram-Positive (Staphylococcus aureus, Bacillus cereus and Clostridium and two Gram-negative bacteria (Escherichia coli and Enterobacter aerogenes). All bismuth MOFs exhibited appreciable to good inhibitory affects against these microorganisms than free linkers. Higher activity was observed against bacillus cereus compared to other strains. The increasing order of the activity for bismuth MOFs against bacillus cereus are MOFs (21)> MOF (18)> MOF (15)> MOF (3)> MOF (5)> MOF (12).
Gov't Doc #: 19162
Appears in Collections:PhD Thesis of All Public / Private Sector Universities / DAIs.

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