Low Loading and High Activity of Platinum Oxide Nanoclusters Formed by Defect Engineering of a Metal-Organic Framework for Formaldehyde Degradation

A distinct platinum oxide nanocluster (PtO_x ) was developed, consisting of only Pt-O bond by a defect-engineered Al metal-organic framework (MOF) (BIT-72) with superior formaldehyde (HCHO) degradation activity and stability. With only 0.015 wt % Pt loading, PtO_x @BIT-72-DE could degrade HCHO with 100 % conversion continuously for at least 200 h under HCHO concentration of 25 ppm and gas hourly space velocity of 60000 mL g^-1  h^-1 at room temperature. Furthermore, its specific rate (446 mmol_HCHO  g_Pt ^-1  h^-1 ) was higher than for traditional Pt-based catalysts and single-atom Pt catalysts. Moreover, the cost of PtO_x @BIT-72-DE was lowered to 0.0769 $ g^-1 , which could significantly facilitate its commercial application. This study demonstrates the promising potential of MOFs in the design of HCHO degradation catalysts.

Intramolecular participation of amino groups in the cleavage and isomerization of ribonucleoside 3'-phosphodiesters: the role in stabilization of the phosphorane intermediate

A dinucleoside-3',5'-phosphodiester model, 5'-amino-4'-aminomethyl-5'-deoxyuridylyl-3',5'-thymidine, incorporating two aminomethyl functions in the 4'-position of the 3'-linked nucleoside has been prepared and its hydrolytic reactions studied over a wide pH range. The amino functions were found to accelerate the cleavage and isomerization of the phosphodiester linkage in both protonated and neutral form. When present in protonated form, the cleavage of the 3',5'-phosphodiester linkage and its isomerization to a 2',5'-linkage are pH-independent and 50-80 times as fast as the corresponding reactions of uridylyl-3',5'-uridine (3',5'-UpU). The cleavage of the resulting 2',5'-isomer is also accelerated, albeit less than with the 3',5'-isomer, whereas isomerization back to the 3',5'-diester is not enhanced. When the amino groups are deprotonated, the cleavage reactions of both isomers are again pH-independent and up to 1000-fold faster than the pH-independent cleavage of UpU. Interestingly, the 2'- to 3'-isomerization is now much faster than its reverse reaction. The mechanisms of these reactions are discussed. The rate accelerations are largely accounted for by electrostatic and hydrogen-bonding interactions of the protonated amino groups with the phosphorane intermediate.