Selective oxidation of β-keto ester modulated by the d-band centers in D-A conjugated microporous metallaphotoredox catalysts containing M−salen (MZn, Cu and Co) and triazine monomers

• Published in: Journal of colloid and interface science 2024-07, Vol.665, p.399-412
• Main Authors: Xie, Lin-Fu, Huang, Wan-Hong, Chen, Jian-Ping, Chen, Hai-Lin, Hou, Cheng, Ni, Qing-Ling, Huang, Ting-Hong, Gui, Liu-Cheng, Wang, Xiu-Jian
• Format: Article
• Language: English
• Subjects: Conjugated microporous polymer; D-band center; Metallaphotoredox catalyst; Oxide intermediate; Photocatalytic selective oxidation
• ISSN: 0021-9797; 1095-7103
• DOI: 10.1016/j.jcis.2024.03.153

Three multiphase metallaphotoredox catalysts M−Salen−CMP (MZn, Cu and Co) with dual-catalytic functions were constructed by linking M−salen (MZn, Cu and Co) and 2, 4, 6-tris(4-ethylphenyl)-1, 3, 5-triazine (TEPT) monomer via covalent bonds. The catalysts M−SATE−CMP (MZn, Cu and Co) have different d-band centers based on different metal active centers, resulting in the difference of the optical property as well as their adsorption and activation capacities for the reactants. Therefore, they can selectively photocatalytically oxidize β-keto esters to α-hydroperoxide β-keto esters (ROOH) or α-hydroxyl β-keto esters (ROH), where ROOH is an intermediate of ROH. [Display omitted] Photocatalytic selective oxidation plays an important role in developing green chemistry. However, it is challenging to design an efficient photocatalyst for controlling the selectivity of photocatalytic oxidation reaction and exploring its detailed mechanism. Here, we synthesized three conjugated microporous polymers (CMPs) with D-A structures, named M−SATE−CMPs (MZn, Cu and Co), with different d-band centers based on different metal centers, resulting in the discrepancy in adsorption and activation capacities for the reactants, which produces the selectivity of β-keto esters being catalyzed into α-hydroperoxide β-keto esters (ROOH) or to α-hydroxyl β-keto esters (ROH). Density functional theory (DFT) calculations also demonstrate that the adsorption and activation capacities of the metal active centers in M−SATE−CMPs (MZn, Cu and Co) for ROOH are the key factors to influence the photocatalytic selective oxidation of β-keto ester. This study provides a promising strategy for designing a metallaphotoredox catalyst whose photocatalytic selectivity depends on the d-band center of metal site in the catalyst.