A Cu-modified Th6-based framework for regulating products in photocatalytic oxidation of tetrahydroisoquinoline†

In order to enhance the diversity of structural components and the synergistic catalytic effect, the monometallic site Cu was loaded in the framework of the Th-MOF to explore its photocatalytic activity and synergistic effect. The Cu-modified Th-MOF photocatalyst (Cu@Th₆-BPYDC, H₂BPYDC = 2,2-bipyridine-5,5-dicarboxylic acid) was designed and synthesized to investigate the effect on the photocatalytic oxidation reaction of 1,2,3,4-tetrahydroisoquinoline (THIQ). Interestingly, it was found that the product type could be modulated by different oxidants. When O₂ was used as the oxidant, the conversion rate of THIQ could reach 94.6% and the 3,4-dihydroisoquinoline product selectivity is 81.0%. When tert-butyl hydroperoxide (TBHP) was used as the oxidant, 99% conversion rate for THIQ and 99% selectivity for the isoquinoline product were obtained. An array of controlled experiments indicated that Cu and Th alternately behaved as the main active centers in the process of regulating the product type, and the synergistic catalysis gave rise to excellent catalytic performance. The results of this work point to a new direction for the design of efficient thorium-based photocatalysts.