Highly efficient visible-light driven photocatalytic reduction of CO2 over g-C3N4 nanosheets/tetra(4-carboxyphenyl)porphyrin iron(III) chloride heterogeneous catalysts

Photocatalytic reduction of CO 2 into value-added chemicals is particularly attractive as it could produce renewable energy and capture greenhouse gas. Photoreduction of CO 2 can be realized over molecular and inorganic catalysts. The former usually exhibit high activity, but low stability and often inactive under visible-light irradiation; the latter has low activity, but good stability. Here we use g-C 3 N 4 nanosheets as the photosensitizer to integrate with Fe tetra(4-carboxylphenyl)porphyrin chloride (FeTCPP) molecular catalyst. Besides π-π stacking between tri- s -triazine unit and porphyrin , the carboxyl group modified Fe porphyrin is used for the first time in CO 2 photoreduction so as to form hydrogen bonding with the rich amino groups in g-C 3 N 4 nanosheets. g-C 3 N 4 /FeTCPP heterogeneous catalysts are prepared via a facile self-assembly approach, in which light harvest is separated from catalysis spatially and temporally. The obtained g-C 3 N 4 /FeTCPP heterogeneous catalysts exhibit high activity for CO 2 reduction under visible-light irradiation, with CO yield of 6.52   mmol   g −1 in 6   h and selectivity up to 98%. Fluorescence data indicate that the electrons can efficiently transfer from the g-C 3 N 4 nanosheets to FeTCPP. The mechanism for CO 2 reduction over the g-C 3 N 4 /FeTCPP heterogeneous catalysts is proposed based on the results of quasi in-situ ESR and UV–vis measurements. This work may pave a facile approach for fabricating the high-efficient photocatalysts for CO 2 reduction, as well as better understanding the related mechanism.