The mononuclear ruthenium complex [Ru(pdc)L 3 ] (H 2 pdc = 2,6-pyridinedicarboxylic acid, L = N-heterocycles such as 4-picoline) has previously shown promising catalytic efficiency toward water oxidation, both in homogeneous solutions and anchored on electrode surfaces. However, the detailed water oxidation mechanism catalyzed by this type of complex has remained unclear. In order to deepen understanding of this type of catalyst, in the present study, [Ru(pdc)(py) 3 ] (py = pyridine) has been synthesized, and the detailed catalytic mechanism has been studied by electrochemistry, UV−vis, NMR, MS, and X-ray crystallography. Interestingly, it was found that once having reached the Ru IV state, this complex promptly formed a stable ruthenium dimer [Ru III (pdc)(py) 2 -O-Ru IV (pdc)(py) 2 ] + . Further investigations suggested that the present dimer, after one pyridine ligand exchange with water to form [Ru III (pdc)(py) 2 -O-Ru IV (pdc)(py)(H 2 O)] + , was the true active species to catalyze water oxidation in homogeneous solutions.

One of the challenges in materials science has been to prepare crystalline inorganic compounds with mesopores. Although several design strategies have been developed to address the challenge, expansion of pore sizes in inorganic materials is more difficult compared to that for metal-organic frameworks. Herein, we designed a novel mesoporous germanate PKU-17 with 3D 48×16×16-ring channels by introducing two large building units (Ge10 and Ge7 clusters) into the same framework. The key for this design strategy is the selection of 2-propanolamine (MIPA), which serves as the terminal species to promote the crystallization of Ge7 clusters. Moreover, it is responsible for the coexistence of Ge10 and Ge7 clusters. To our knowledge, the discovery of PKU-17 sets a new record in pore sizes among germanates. It is also the first germanate that exhibits a good selectivity toward CO2 over N2 and CH4 .

One of the challenges in materials science has been to prepare crystalline inorganic compounds with mesopores. Although several design strategies have been developed to address the challenge,e xpansion of pore sizes in inorganic materials is more difficult compared to that for metal-organic frameworks.Herein, we designed an ovel mesoporous germanate PKU-17 with 3D 48 1616-ring channelsb yi ntroducing two large building units (Ge 10 and Ge 7 clusters) into the same framework. The key for this design strategy is the selection of 2-propanolamine (MIPA), whichs erves as the terminal species to promote the crystallization of Ge 7 clusters. Moreover,itisresponsible for the coexistence of Ge 10 and Ge 7 clusters.Toour knowledge,the discovery of PKU-17 sets anew recordi np ore sizes among germanates.I ti sa lso the first germanate that exhibits agood selectivity toward CO 2 over N 2 and CH 4 .