Cobalt Phthalocyanine Immobilized on Graphene Oxide: An Efficient Visible-Active Catalyst for the Photoreduction of Carbon Dioxide

New graphene oxide (GO)-tethered–CoII phthalocyaninecomplex [CoPc–GO] was synthesized by a stepwiseprocedure and demonstrated to be an efficient, cost-effectiveand recyclable photocatalyst for the reduction of carbondioxide to produce methanol as the main product. The developedGO-immobilized CoPc was characterized by X-raydiffraction (XRD), FTIR, XPS, Raman, diffusion reflection UV/Vis spectroscopy, inductively coupled plasma atomic emissionspectroscopy (ICP-AES), thermogravimetric analysis(TGA), Brunauer–Emmett–Teller (BET), scanning electron microscopy(SEM), and transmission electron microscopy (TEM).FTIR, XPS, Raman, UV/Vis and ICP-AES along with elementalanalysis data showed that CoII–Pc complex was successfullygrafted on GO. The prepared catalyst was used for the photocatalyticreduction of carbon dioxide by using water asa solvent and triethylamine as the sacrificial donor. Methanolwas obtained as the major reaction product along with theformation of minor amount of CO (0.82 %). It was found thatGO-grafted CoPc exhibited higher photocatalytic activitythan homogeneous CoPc, as well as GO, and showed goodrecoverability without significant leaching during the reaction.Quantitative determination of methanol was done byGC flame-ionization detector (FID), and verification of productwas done by NMR spectroscopy. The yield of methanolafter 48 h of reaction by using GO–CoPc catalyst in the presenceof sacrificial donor triethylamine was found to be3781.8881 mmolg 1 cat., and the conversion rate was foundto be 78.7893 mmolg 1cat.h 1. After the photoreduction experiment,the catalyst was easily recovered by filtration andreused for the subsequent recycling experiment without significantchange in the catalytic efficiency