Photocatalytic activity enhancement with 4-cyanophenylacetylene-modified Cu₂O cubes and rhombic dodecahedra and use in arylboronic acid hydroxylation

Abstract

Surface 4-cyanophenylacetylene (4-CNA) functionalization turned inert Cu2O cubes to possess a high photocatalytic activity. The modified rhombic dodecahedra also exhibited large activity enhancement, but decorated octahedra showed only moderate activity...

Photocatalytic activity enhancement with 4-trifluoromethylphenylacetylene-functionalized Cu2O cubes and rhombic dodecahedra from band structure modulation and use in boronic acid hydroxylation

“…34 Previously, when methanol was also used as the solvent to probe superoxide radical production, a characteristic 6-peak feature in the EPR spectrum was obtained, so superoxide radicals should also form in the photocatalytic process. 22,35 A lower EPR peak intensity for the functionalized octahedra also matches the photocatalysis results. For Cu 2 O rhombic dodecahedra, there is a recognizable decrease in EPR peak intensity with 4-TFMA modification.…”

“…This is normally the case and is related to changes in the surface band structure of Cu 2 O and electron density with molecular bonding. 22…”

“…Functionalization with electron-donating 4-ethynylaniline (4-EA) and electron-withdrawing 4-cyanophenylacetylene (4-CNA) can boost photocatalytic performance of Cu 2 O cubes and rhombic dodecahedra, but these molecules are much less effective for octahedra. 21,22 2-Ethynyl-6-methoxynaphthalene (2E-6MN)-modified Cu 2 O cubes containing an electron-donating methoxy group delivered less photocatalytic improvement. 23 On the basis of electron-donating and -withdrawing group considerations, 4-trifluoromethylphenylacetylene with a highly electronegative and strongly electron-withdrawing –CF 3 group should be an interesting molecule to examine its effectiveness in promoting photocatalytic activity.…”

“…24 In addition to dye photodegradation, the 4-TFMA-modified Cu 2 O crystals should also find use in catalyzing some organic transformations such as arylboronic acid hydroxylation. 22,25 The use of functionalized Cu 2 O crystals for catalyzing organic reactions offers tremendous time and cost advantages over metal–organic framework (MOF) and covalent organic framework (COF) photocatalysts. 26–29 Previously, 4-NA-modified Cu 2 O crystals have also been shown to photocatalyze the aryl sulfide oxidation reaction.…”

Photocatalytic Oxidative Amine Coupling with 4-Nitrophenylacetylene-Modified Cu2O Polyhedra

“…Holes should participate in the oxidative amine coupling process. When KBrO 3 was introduced as an electron scavenger, benzylamine conversion to N -benzylidenebenzylamine dropped to 51%, so photogenerated electrons transferring to 4-NA should take place . Next, adding 2-propanol as a hydroxyl radical scavenger resulted in a moderate product decrease to 83%, so • OH formation is less important to oxidative amine coupling.…”