Photocatalytic Reduction of CO2 by Highly Efficient Homogeneous FeII Catalyst based on 2,6-Bis(1’,2’,3’-triazolyl-methyl)pyridine. Comparison with Analogues.

Abstract

Fully earth-abundant and highly efficient systems for producing syngas CO/H2 through photocatalytic reduction from CO2 are essential to approach a sustainable way of closing the carbon cycle. Herein, the synthesis and characterization of a new iron complex, FeIIL(NCS)2py, coordinated to an N,N,N-pincer ligand 2,6-bis(4’-phenyl-1’,2’,3’-triazol-1’-yl-methyl)pyridine (L), two isothiocyanate groups (NCS) and one pyridine is reported. Its catalytic activity in the photo-driven reduction of carbon dioxide has been investigated and compared with its CoII analogue (CoL(NCS)2py) and their homoleptic complexes ML2. In this work, the catalysts are used in combination with the heteroleptic complex [CuI(dmp)(DPEphos)], where dmp is 2,9-dimethyl-1,10-phenanthroline and DPEPhos is bis[(2-diphenylphosphino)phenyl] ether, to reach entirely earth-abundant systems. The new iron heteroleptic complex FeIIL(NCS)2py showed considerable activity with a TONCO of 576 obtained after 4 h (TOF=144 h−1) through visible light (λ=420 nm) and a quantum yield of 7.1 %.