Green Synthesis of a Microporous, Partially Fluorinated Zn super(II) Paddlewheel Metal-Organic Framework: H sub(2)/CO sub(2) Adsorption Behavior and Solid-State Conversion to a ZnO-C Nanocomposite

• Published in: European journal of inorganic chemistry Vol. 2015; no. 34; pp. 5669 - 5676
• Main Authors: Dhankhar, Sandeep Singh, Kaur, Manjodh, Nagaraja, C M
• Format: Journal Article
• Language: English
• Published: 01.12.2015
• Subjects: Carbon dioxide; Conversion; Fluorination; Metal-organic frameworks; Metalorganic compounds; Nanocomposites; Self assembly; Synthesis; Three dimensional
• ISSN: 1434-1948; 1099-0682
• DOI: 10.1002/ejic.201500975

A microporous, partially fluorinated metal-organic framework consisting of Zn super(II) dimeric paddlewheel units, formulated as [Zn(hfipbba)(4bpdb) sub(0.5)]. H sub(2)O (1) [hfipbba = 4,4'-(hexaflouroisopropylene)bis(benzoic acid); 4bpdb = 1,4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene], was synthesized by room-temperature self-assembly and characterized structurally by single-crystal XRD. Compound 1 adopts a 3D microporous framework structure constituted by six-connected Zn super(II) dimeric paddlewheel nodes with {4 super(4).6 super(10).8}-ne t topology. Further, rapid synthesis of phase-pure 1 by green synthetic approaches such as mechanochemical and sonochemical routes was achieved. The 3D framework of 1 houses 1D helical channels with narrow pore dimensions of about 3.114.17 Aa and exhibits interesting gas-uptake (H sub(2)/CO sub(2)) properties. The isosteric heats of adsorption Q sub(st) for H sub(2) and CO sub(2) were estimated to be 8.8 and 36.4 kJmol super(-1), respectively. Interestingly, solid-state conversion of 1 to phase-pure hexagonal ZnO nanocrystals of 6.1 plus or minus 0.63 nm in size, embedded in carbonaceous layers to form a ZnO-C nanocomposite (NC), occurred on heating of 1 to 600 degree C under vacuum for 2 h. The ZnO-C NC was characterized by XRD, UV/Vis, energy-dispersive X-ray, and TEM analyses. The as-synthesized ZnO-C NC exhibits good photocatalytic activity for the degradation of methylene blue. A microporous, partially fluorinated MOF consisting of Zn super(II) dimeric paddlewheel units was synthesized by room-temperature self-assembly of Zn super(II) ions with a mixed-ligand system and characterized by single-crystal XRD. It exhibits interesting gas-uptake (H sub(2)/CO sub(2)) properties, and its solid-state conversion to a ZnO-C nanocomposite was demonstrated.