It is a great challenge to develop iron-based highly-efficient and durable catalytic systems for the hydrogen evolution reaction (HER) by understanding and learning from [FeFe]-hydrogenases. Here we report photocatalytic H production by a hybrid assembly of a sulfonate-functionalized [FeFe]-hydrogenase mimic (1) and CdSe quantum dot (QD), which is denoted as 1/β-CD-6-S-CdSe (β-CD-6-SH = 6-mercapto-β-cyclodextrin). In this assembly, thiolato-functionalized β-CD acts not only as a stabilizing reagent of CdSe QDs but also as a host compound for the diiron catalyst, so as to confine CdSe QDs to the space near the site of diiron catalyst. In addition, another two reference systems comprising MAA-CdSe QDs (HMAA = mercaptoacetic acid) and 1 in the presence and absence of β-CD, denoted as 1/β-CD/MAA-CdSe and 1/MAA-CdSe, were studied for photocatalytic H evolution. The influences of β-CD and the stabilizing reagent β-CD-6-S on the stability of diiron catalyst, the fluorescence lifetime of CdSe QDs, the apparent electron transfer rate, and the photocatalytic H-evolving efficiency were explored by comparative studies of the three hybrid systems. The 1/β-CD-6-S-CdSe system displayed a faster apparent rate for electron transfer from CdSe QDs to the diiron catalyst compared to that observed for MAA-CdSe-based systems. The total TON for visible-light driven H evolution by the 1/β-CD-6-S-CdSe QDs in water at pH 4.5 is about 2370, corresponding to a TOF of 150 h in the initial 10 h of illumination, which is 2.7- and 6.6-fold more than the amount of H produced from the reference systems 1/β-CD/MAA-CdSe and 1/MAA-CdSe. Additionally, 1/β-CD-6-S-CdSe gave 2.4-5.1 fold enhancement in the apparent quantum yield and significantly improved the stability of the system for photocatalytic H evolution.

Copper complexes with a general formula of [(L)Cu(OH2)](BF4)2 (1, L1=N,N′‐dimethyl‐N,N′‐bis(pyridin‐2‐ylmethyl)‐1,2‐diaminoethane; 2, L2=N,N′‐bis(pyridin‐2‐ylmethyl)piperazine); 3, L3=N,N′‐bis(pyridin‐2‐ylmethyl)diazepane) were prepared as molecular catalysts for oxygen evolution reaction. These catalysts have the same first coordination environment but different backbones of diamine‐dipyridine N4‐ligands. Single crystal X‐ray diffraction studies on the molecular structures of 1–3 revealed that the backbone rigidity of the N4‐ligand has apparent influence on the Npy−Cu−N′py open angle of copper complexes. Comparative studies manifested that the subtle structural change caused by the backbone rigidity of N4‐ligands has an important influence on the catalytic performance and reaction pathway of copper catalysts for electrochemical water splitting.

The [FeFe]-hydrogenase model, [(μ-bdt)­Fe2(CO)6] (1, bdt = benzene-1,2-dithiolato), displays distinctive activity from its analogous complex, [(μ-edt)­Fe2(CO)6] (2, edt = ethane-1,2-dithiolato), for electrochemical CO2 reduction in acetonitrile with methanol or water as proton source. The maximum turnover frequency of 195 s–1 estimated for 1 is more than 4800 times higher than that of 2. The influence of reaction conditions on faradaic yield and product selectivity was investigated. Controlled potential electrolysis experiments of 1 under optimal conditions gave a good faradaic yield of 88%, with formic acid as major product (selectivity ≈81%) together with a small amount of CO (selectivity ≈ 11%) and H2 (selectivity ≈ 8%). Density functional theory calculations suggest a mechanism of bimetal synergistic catalysis for electrochemical CO2 reduction by 1.