Green Synthesis of a Microporous, Partially Fluorinated Zn II Paddlewheel Metal–Organic Framework: H 2 /CO 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
• ISSN: 1434-1948; 1099-0682
• DOI: 10.1002/ejic.201500975

Abstract A microporous, partially fluorinated metal–organic framework consisting of Zn II dimeric paddlewheel units, formulated as [Zn(hfipbba)(4bpdb) 0.5 ] · H 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 II dimeric paddlewheel nodes with {4 4 .6 10 .8}‐net 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 3.11 × 4.17 Å and exhibits interesting gas‐uptake (H 2 /CO 2 ) properties. The isosteric heats of adsorption Q st for H 2 and CO 2 were estimated to be 8.8 and 36.4 kJ mol –1 , respectively. Interestingly, solid‐state conversion of 1 to phase‐pure hexagonal ZnO nanocrystals of 6.1 ± 0.63 nm in size, embedded in carbonaceous layers to form a ZnO–C nanocomposite (NC), occurred on heating of 1 to 600 °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.