Research Institute of Photocatalysis, State Key Laboratory of Photocatalysis on Energy and Environment, College of Chemistry , Fuzhou University , Fuzhou , 350116 , P. R. China.
Instituto de Tecnología Química , Universitat Politècnica de València-Consejo Superior de Investigaciones Científicas , Avenida de los Naranjos s/n , 46022 Valencia , Spain.
Inorg Chem. 2018 Jul 16;57(14):8276-8286. doi: 10.1021/acs.inorgchem.8b00896. Epub 2018 Jul 2.
Using the open N,N'-chelating sites of MOF-253 (Al(OH)(dcbpy), dcbpy = 2,2'-bipyridine-5,5'-dicarboxylic acid) to coordinate with Re(I), a linker anchored Re complex MOF-253-Re(CO)Cl active for photocatalytic CO reduction was obtained. Unlike the homogeneous bipyridine containing Re complexes which produce CO during photocatalytic CO reduction, formate was obtained as the main CO reduction product over the as-obtained MOF-253-Re(CO)Cl. The linker anchored MOF-253-Re(CO)Cl showed superior photocatalytic performance compared to its homogeneous counterpart since the usual formation of the bimolecular Re intermediate leading to the deactivation of the homogeneous Re complex was significantly inhibited in the MOF supported Re complex. To enhance its light absorption, a linker anchored Ru sensitizer was simultaneously constructed in MOF-253-Re(CO)Cl (Ru-MOF-253-Re). The total TON (TON is defined as mole of the evolved H, CO, and HCOO over per amount of Rhenium) for CO reduction (28.8 in 4 h) over the as-obtained Ru-MOF-253-Re system is comparable or even superior to most already reported Re carbonyl complexes featuring bpy ligands and the Ru-Re bimetallic supramolecular systems constructed via the covalent bond under similar reaction conditions. The enhanced photocatalytic CO reduction over the Ru-MOF-253-Re can be ascribed to the improved visible light absorption and the existence of an efficient photoinduced charge transfer from Ru sensitizer to Re catalytic center, as evidenced from the transient absorption studies. The use of MOF-253 as a metalloligand and support to assemble the Ru-Re system as well as a mediator to promote the charge transfer from Ru sensitizer to Re catalytic center resembles the construction of Ru-Re supramolecular structures using covalent bonds, but is more facile in preparation and provides more flexibility. This study demonstrates the possibility of using MOFs with open coordination sites as a platform for the construction of a stable multifunctional hybrid system for artificial photosynthesis.
利用 MOF-253（Al(OH)(dcbpy)，dcbpy=2,2'-联吡啶-5,5'-二羧酸）的开放 N,N'-螯合位点与 Re(I)配位，得到了用于光催化 CO 还原的锚定在配体上的 MOF-253-Re(CO)Cl 配合物。与在光催化 CO 还原过程中产生 CO 的均相含联吡啶的 Re 配合物不同，在获得的 MOF-253-Re(CO)Cl 上，主要得到的 CO 还原产物是甲酸盐。与均相对应物相比，锚定在配体上的 MOF-253-Re(CO)Cl 表现出更高的光催化性能，因为通常形成双分子 Re 中间体导致均相 Re 配合物失活的反应在 MOF 负载的 Re 配合物中受到显著抑制。为了增强其光吸收，同时在 MOF-253-Re(CO)Cl 中构建了锚定在配体上的 Ru 敏化剂（Ru-MOF-253-Re）。在获得的 Ru-MOF-253-Re 体系中，CO 还原的总 TON（TON 定义为每摩尔铼生成的 H、CO 和 HCOO 的摩尔数）（4 h 内为 28.8）与具有 bpy 配体的大多数已报道的 Re 羰基配合物和通过共价键构建的 Ru-Re 双金属超分子体系相当，甚至更高。在 Ru-MOF-253-Re 上增强的光催化 CO 还原可归因于可见光吸收的提高和从 Ru 敏化剂到 Re 催化中心的有效光诱导电荷转移的存在，这从瞬态吸收研究中得到了证实。使用 MOF-253 作为金属配体和支架来组装 Ru-Re 体系以及作为促进从 Ru 敏化剂到 Re 催化中心的电荷转移的介质类似于使用共价键构建 Ru-Re 超分子结构，但在制备方面更简单，并提供了更大的灵活性。这项研究证明了使用具有开放配位位点的 MOFs 作为构建稳定多功能杂化系统用于人工光合作用的可能性。
