Green Synthesis of a Microporous, Partially Fluorinated ZnII Paddlewheel Metal–Organic Framework: H2/CO2 Adsorption Behavior and Solid‐State Conversion to a ZnO–C Nanocomposite

Abstract

AbstractA microporous, partially fluorinated metal–organic framework consisting of ZnII dimeric paddlewheel units, formulated as [Zn(hfipbba)(4bpdb)0.5]·H2O (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 ZnII dimeric paddlewheel nodes with {44.610.8}‐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 (H2/CO2) properties. The isosteric heats of adsorption Qst for H2 and CO2 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.