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

Cheng Lin; Zhen Shan; Chaoran Dong; Yuan Lu; Weikun Meng; Gen Zhang; Bo Cai; Guanyong Su; Jong Hyeok Park; Kan Zhang

doi:10.1126/sciadv.adi9442

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

Sci Adv. 2023 Nov 10;9(45):eadi9442. doi: 10.1126/sciadv.adi9442. Epub 2023 Nov 8.

Authors

Cheng Lin^{1

2}, Zhen Shan¹, Chaoran Dong¹, Yuan Lu², Weikun Meng¹, Gen Zhang¹, Bo Cai³, Guanyong Su¹, Jong Hyeok Park², Kan Zhang¹

Affiliations

¹ Nanjing University of Science and Technology, Nanjing 210094, China.
² Department of Chemical and Biomolecular Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 120-749, Republic of Korea.
³ Institute of Advanced Materials, Nanjing University of Posts and Telecommunications, Nanjing 210023, China.

Abstract

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 (BiVO₄) 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/BiVO₄ 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.