Jinjing Qiu,Qi Chen,Cheng Liu,Yueling Chen,Jionghua Wu,Kaiqiang Jing,Jimmy C. Yu,Ling Wu,Xianzhi Fu
Defect engineering and single atom incorporation can provide more active sites to modulate the surface electronic structure of a catalyst and to activate reactant molecules. Herein, a series of Ru-anchored DUT-67(Zr) MOFs with explicit defect sites have been prepared for photocatalytic nitrogen reduction. It is characterized that Ru/DUT-67(Zr) possesses uniformly dispersed Ru single atoms and unsaturated Zr. Typically, 1.0 %Ru/DUT-67(Zr) shows best performance with a NH 4 + yield of 61.1 μmol·g −1 ·h −1 , which is approximately 6-folds higher than that of defective DUT-67(Zr) without Ru single atom (DUT-L), while pristine DUT-67(Zr) exhibits a lack of the photocatalytic N 2 reduction activity. The observed enhancement can be attributed to the introduction of Ru and unsaturated Zr sites induced by irradiation. Both of them can work together act as active centers to absorb and activate dinitrogen molecule. Furthermore, benefited from the electronic channel (Ru-S) between Ru and DUT-67(Zr), the separation of photogenerated carriers has been greatly improved, contributing to the collaborative conversion of activated N 2 to NH 3 . This study provides a new insight for designing a dual active sites photocatalyst with unsaturated coordinated sites and the single atoms by the coordinately interaction of functionalized linker.
The highly efficient production of furfuryl alcohol (FFA) from biomass-derived furfural (FFR) is attracting increasing attention due to its wide application in the production of value-added chemicals. Zr-based MOF-808 is promising for liquid catalytic transfer hydrogenation (CTH) of FFR to FFA in terms of possessing a great number of Lewis-acid sites. Herein, a series of defective MOF-808 (D x -MOF-808) samples were prepared via a competitive coordination-removal strategy by modulating with benzoic acid (HBC). HBC was introduced as the temporary ligand for competing with formal ligand 1,3,5-benzenetricarboxylic acid (H 3 BTC) to coordinate with metal clusters and then it was removed with methanol to obtain the D x -MOF-808. The results showed that HBC serves not only as a temporary ligand participating in the synthesis of MOF-808 to obtain defective structure but also as a modulator controlling the particle size by terminating the growth of crystals. By changing the amount of HBC addition, the degree of ligand deficiency and the number of exposed Zr sites can be well regulated. Especially, excellent performance of FFR conversion (99%), FFA selectivity (94.4%) and FFA formation rate (48.6 mmol·g −1 ·h −1 ) was achieved over D 40 -MOF-808 sample with 2-propanol as a hydrogen donor under mild conditions (90 °C, 2 h), ranking it the best among the reported catalysts. Detailed characterizations proved that the high activity of D 40 -MOF-808 was jointly influenced by the high surface area, the high content of exposed Zr metal sites and ligand deficiency.
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