Reactions in the Photocatalytic Conversion of Tertiary Alcohols on Rutile TiO₂(110)

Abstract

According to textbooks, tertiary alcohols are inert towards oxidation. The photocatalysis of tertiary alcohols under highly defined vacuum conditions on a titania single crystal reveals unexpected and new reactions, which can be described as disproportionation into an alkane and the respective ketone. In contrast to primary and secondary alcohols, in tertiary alcohols the absence of an α‐H leads to a C−C‐bond cleavage instead of the common abstraction of hydrogen. Surprisingly, bonds to methyl groups are not cleaved when the alcohol exhibits longer alkyl chains in the α‐position to the hydroxyl group. The presence of platinum loadings not only increases the reaction rate but also opens up a new reaction channel: the formation of molecular hydrogen and a long‐chain alkane resulting from recombination of two alkyl moieties. This work demonstrates that new synthetic routes may become possible by introducing photocatalytic reaction steps in which the co‐catalysts may also play a decisive role.

Regulating Photochemical Selectivity with Temperature: Isobutanol on TiO2(110)

“…Oxygen is known to promote alkoxy formation, ,,, the key intermediate for the first photo-oxidation step and, consequently, the largest yield in photoproducts are observed on oxidized-TiO 2 (110). Surface hydroxylation resembling water present on the surface did not change the photochemical conversion of alkoxy species in line with observations for other alcohols. , Therefore, the pressure of O 2 during photocatalytic transformation of alcohols will be a critical factor in determining rates.…”

“…The reaction occurs on all three surface preparations qualitatively similar, and isobutanal, propane, and CO are always obtained (Figure S13). The observation of gaseous propane shows that hydrogen is abstracted from the surface during this process, in agreement with the alkane formation from the photoreforming of tertiary alcohols on TiO 2 (110) via a C–C split …”

Anion-Exchange-Mediated Internal Electric Field: Boosting Photogenerated Carrier Separation and Utilization

“…During photocatalysis, the separation of electron-hole pairs within the semiconductor catalysts, combined with the following energy transfer processes, can readily generate a large amount of highly active species (such as radicals and singlet oxygen [1][2][3][4] . Notably, these active species could, under green and mild conditions, participate in a variety of organic reactions, including hydrogenation 5,6 , epoxidation 7,8 , alcohol oxidation 9,10 , selective oxidation of aromatic compounds 11,12 , and even some reactions that are rather challenging in thermal catalysis. Yet still, currently for heterogeneous photocatalysts, there exist the common issues of rapid recombination of photocarriers and the resulting low e ciency of carrier separation and utilization, which would hamper the high-performance catalysis of sophisticated organic reactions, and thus their applications have so far been limited primarily to environment-related aspects such as degradation of organics, air puri cation and water photolysis [13][14][15][16][17] .…”

Anion-exchange-mediated internal electric field for boosting photogenerated carrier separation and utilization

“…During photocatalysis, the separation of electron-hole pairs within the semiconductor catalysts, combined with the following energy transfer processes, can readily generate a large amount of highly active species (such as radicals and singlet oxygen 1 – 4 . Notably, these active species could, under green and mild conditions, participate in a variety of organic reactions, including hydrogenation 5 , 6 , epoxidation 7 , 8 , alcohol oxidation 9 , 10 , selective oxidation of aromatic compounds 11 , 12 , and even some reactions that are rather challenging in thermal catalysis. Yet still, currently for heterogeneous photocatalysts, there exist the common issues of rapid recombination of photocarriers and the resulting low efficiency of carrier separation and utilization, which would hamper the high-performance catalysis of organic reactions, and thus their applications have so far been limited primarily to environment-related aspects such as degradation of organics, air purification and water photolysis 13 – 17 .…”