Covalent organic frameworks bearing Ni active sites for free radical-mediated photoelectrochemical organic transformations

• DOI: 10.1126/sciadv.adi9442
• Publication Date: 2023-11-08T18:58:31Z
• Authors: Cheng Lin; Zhen Shan; Chaoran Dong; Yuan Lu; Weikun Meng; Gen Zhang; Bo Cai; Guanyong Su; Jong Hyeok Park; Kan Zhang

Photoelectrochemical (PEC) organic transformations occurring at anodes are a promising strategy for circumventing the sluggish kinetics of the oxygen evolution reaction. Here, we report a free radical-mediated reaction instead of direct hole transfer occurring at the solid/liquid interface for PEC oxidation of benzyl alcohol (BA) to benzaldehyde (BAD) with high selectivity. A bismuth vanadate (BiVO 4 ) photoanode coated with a 2,2′-bipyridine–based covalent organic framework bearing single Ni sites (Ni-TpBpy) was developed to drive the transformation. Experimental studies reveal that the reaction at the Ni-TpBpy/BiVO 4 photoanode followed first-order reaction kinetics, boosting the formation of surface-bound ·OH radicals, which suppressed further BAD oxidation and provided a nearly 100% selectivity and a rate of 80.63 μmol hour −1 for the BA-to-BAD conversion. Because alcohol-to-aldehyde conversions are involved in the valorizations of biomass and plastics, this work is expected to open distinct avenues for producing key intermediates of great value.