Photoinduced Oxygen Atom Transfer to α‐Pinene and R‐Carvone using a Dioxo‐Molybdenum (VI) Complex Incorporated within a Modified UiO‐67 (Zr/Ti) MOF

Abstract

We report a highly selective (100 %) epoxidation of α‐pinene and R‐carvone using an oxygen atom transfer (OAT) reaction facilitated by a dioxo‐Mo complex (Mo(VI)O2Cl2Ln) incorporated into the ligand 5,5’‐dicarboxylate‐2,2’‐bipyridine (bpydc) within a Metal‐Organic Framework (MOF) type UiO‐67. Photo‐stimulated (350 nm) OAT reaction was carried out with oxygen molecular used as the oxidant for 10 h. UiO‐67 was synthesized with a mixture of the ligands 2,2'‐biphenyl‐5,5'‐dicarboxylate (bpdc) and 2,2‐bipyridine‐5,5‐dicarboxylate (bpydc) in different molar ratios (67:33, 50:50, 70:30, 0:100 bpdc:bpydc) to promote a higher presence of catalytic sites, i.e., the dioxo‐Mo complex units. Furthermore, a post‐synthetic exchange of Zr for Ti, between 64:36 to 78:22 Ti:Zr molar ratio, was performed to improve the optical properties of the MOF and promote the photoinduced OAT reaction. The Catalytic system was characterized by FTIR, XRD, 1H NMR, XPS, TGA, N2 adsorption/desorption and UV‐Vis‐DR. The amount of the epoxide monoterpene is proportional to the number of the dioxomolybdenum(VI) units (MoO2) incorporated in the UiO‐67 (Zr/Ti), and the OAT reaction selectivity is due to the absence of the oxygen radicals in the medium of reaction. Besides, The Mo complex exhibited excellent stability after five cycles of use.

Aggrandized photocatalytic H2O2 and H2 production by a TiO2/Ti3C2–TiC/mixed metal Ce–Zr MOF composite: an interfacial engineered solid-state-mediator-based Z-scheme heterostructure

“…From the Nyquist plot, it can be clearly seen that after modifying TiO 2 /Ti 3 C 2 –TiC with CZUNH, the resulting TiO 2 /Ti 3 C 2 –TiC/CZUNH-20 hybrid exhibits a reduced arc radius and diminished vertical line as compared to the pristine materials, which indicates the presence of a tight interfacial junction between TiO 2 /Ti 3 C 2 –TiC and CZUNH and enhanced charge carrier transfer across the heterojunction. 63–65 Hence, the EIS analysis of the TiO 2 /Ti 3 C 2 –TiC/CZUNH-20 hybrid confirmed the reduced charge transfer resistance, enhanced charge flux and higher electrical conductivity at the electrode–electrolyte interface and hence the increased charge shuttling.…”