EfficientphotocatalyticreductionofCO2toformatebyamolecularnoblemetal-freesystem<iclass="icon-zqcb"></i>

Reducing CO2 to carbon-neutral solar fuels can not only alleviate the energy demand but also mitigate the greenhouse effect.At present,developing an efficient non-noble metal photo/electrocatalytic system for converting CO2 to a specific product beyond CO is still a big challenge.Herein,we report a new cobalt complex bearing 2,2′-bi-1,10-phenanthroline ligand that can photocatalytically reduce CO2 to formate （HCOO-）.Turnover number （TON） for HCOO-up to 677 with 99%selectivity can be achieved using organic dyes purpurin as photosensitizer and 1,3-dimethyl-2-phenyl-2,3-dihydro-1H-benzo[d]imidazole （BIH） as sacrificial reductant in a CO2-saturated NMP/TEA （v/v,3:1） solution under visible light irradiation.Controlled potential electrolysis at-1.41 V （vs.Ag/Ag Cl） in the presence of 12 m M Et3NHBF4 also produced HCOO-with Faradaic efficiency of 39%.Spectroscopic and electrochemical studies suggest that a[CoI-H]species is the key intermediate for CO2 reduction.