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.
Yun Huang,Qi Chen,Yueling Chen,Zefeng Yang,Jionghua Wu,Jimmy C. Yu,Ling Wu
The generation of active hydrogen species (H*) is an essential step in the photocatalytic conversion of nitrogen molecules (N 2 ) to ammonia (NH 3 ). Metal-organic frameworks (MOFs) are versatile porous structures but they do not exhibit sufficient photocatalytic activities for nitrogen fixation. Adding appropriate amounts of noble metal species as a cocatalyst to MOFs can often improve their activities. This work uses a photoreduction strategy to reduce the right amount of Pt 4+ to Pt clusters, and confines the remaining Pt 4+ uniformly onto DUT-67(Zr). This is realized by taking advantage of a unique Pt-S electron channel, and the unsaturated Zr sites are concurrently in-situ generated under light exposure. The unsaturated Zr sites adsorb and activate N 2 , while the Pt clusters are involved in the water splitting process on DUT-67(Zr) to generate more H*, leading to continuous H* supply that would speed up the catalytic hydrogenation of nitrogen intermediate NH x . The Pt-S electronic channel formed between highly dispersed single atoms Pt and DUT-67(Zr) facilitates the separation and transfer of photo-generated charge carriers. Consequently, with the synergistic effect of unsaturated Zr sites, Pt clusters and Pt-S electron channels, a high photocatalytic nitrogen fixation performance of 78.8 μmol g ‒1 h ‒1 can be achieved. This is 10.4 times higher than that of the sample DUT-67-L with only unsaturated Zr sites and no Pt loading. This work provides an insight to rational design of uniform dispersed precious metal-based MOF photocatalyst for efficient photocatalytic ammonia synthesis.
Wang Tao,Hu Aiyun,Xu Guangzhi,Liu Chen,Wang Haijun,Xia Yongmei
Furfural (FAL) is one of the most important biomass-derived platform compounds. The catalytic transformation of FAL was investigated with three porous Zr–thiophenedicarboxylate hybrids for the production of furfuryl alcohol (FOL). Three Zr-based catalysts, including DUT-67(Zr), DUT-68(Zr) and DUT-69(Zr) were synthesized through a facile assembly of 2,5-thiophenedicarboxylate acid with ZrCl 4 using the acetic acid as a modulator under hydrothermal conditions. These catalysts were also characterized using FT-IR, XRD, SEM, TEM, N 2 adsorption–desorption, XPS and TG. The specific surface area of the DUT-69(Zr) is smaller than that of the DUT-68(Zr) and slightly larger than that of the DUT-67(Zr), but it has a relatively large pore volume and pore diameter. Although all three catalysts showed excellent catalytic activity towards the catalytic transfer hydrogenation of FAL into FOL, the DUT-69(Zr) material has slightly higher catalytic activity than the other two catalysts. Besides, considering the cost of catalyst preparation, the DUT-69(Zr) material was used as the optimal catalyst and studied in detail. A high FOL yield of 92.2% at 95.9% FAL conversion was achieved at 120 °C for 4 h over DUT-69(Zr). Meanwhile, the DUT-69(Zr) could be reused more than six times with a minor decrease in catalytic activity. Finally, a plausible mechanism for catalytic transfer hydrogenation of carbonyl compounds to produce corresponding alcohols was presented based on the results of the experiments and previous reports. Graphical Abstract
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