Bridging the Gap between Charge Storage Site and Transportation Pathway in Molecular-Cage-Based Flexible Electrodes.

Porous materials have been widely applied for supercapacitors; however, the relationship between the electrochemical behaviors and the spatial structures has rarely been discussed before. Herein, we report a series of porous coordination cage (PCC) flexible supercapacitors with tunable three-dimensional (3D) cavities and redox centers. PCCs exhibit excellent capacitor performances with a superior molecular capacitance of 2510 F mmol-1, high areal capacitances of 250 mF cm-2, and unique cycle stability. The electrochemical behavior of PCCs is dictated by the size, type, and open-close state of the cavities. Both the charge binding site and the charge transportation pathway are unambiguously elucidated for PCC supercapacitors. These findings provide central theoretical support for the "structure-property relationship" for designing powerful electrode materials for flexible energy storage devices.

Modeling the Enzyme Specificity by Molecular Cages through Regulating Reactive Oxygen Species Evolution.

Mimicking the active site and the substrate binding cavity of the enzyme to achieve specificity in catalytic reactions is an essential challenge. Herein, porous coordination cages (PCCs) with intrinsic cavities and tunable metal centers have proved the regulation of reactive oxygen species (ROS) generating pathways as evidenced by multiple photo-induced oxidations. Remarkably, in the presence of the Zn4 -µ4 -O center, PCC converted dioxygen molecules from triplet to singlet excitons, whereas the Ni4 -µ4 -O center promoted the efficient dissociation of electrons and holes to conduct electron transfer towards substrates. Accordingly, the distinct ROS generation behavior of PCC-6-Zn and PCC-6-Ni enables the conversion of O2 to 1 O2 and O2 ⋅- , respectively. In contrast, the Co4 -µ4 -O center combined the 1 O2 and O2 ⋅- together to generate carbonyl radicals, which in turn reacted with the oxygen molecules. Harnessing the three oxygen activation pathways, PCC-6-M (M=Zn/Ni/Co) display specific catalytic activities in thioanisole oxidation (PCC-6-Zn), benzylamine coupling (PCC-6-Ni), and aldehyde autoxidation (PCC-6-Co). This work not only provides fundamental insights into the regulation of ROS generation by a supramolecular catalyst but also demonstrates a rare example of achieving reaction specificity through mimicking natural enzymes by PCCs.

Glucose/Graphene-Based Aerogels for Gas Adsorption and Electric Double Layer Capacitors.

In this study, three-dimensional glucose/graphene-based aerogels (G/GAs) were synthesized using the hydrothermal reduction and CO2 activation method. Graphene oxide (GO) was used as a matrix, and glucose was used as a binder for the orientation of the GO morphology in an aqueous media. We determined that G/GAs exhibited narrow mesopore size distribution, a high surface area (763 m² g-1), and hierarchical macroporous and mesoporous structures. These features contributed to G/GAs being promising adsorbents for the removal of CO2 (76.5 mg g-1 at 298 K), CH4 (16.8 mg g-1 at 298 K), and H2 (12.1 mg g-1 at 77 K). G/GAs presented excellent electrochemical performance, featuring a high specific capacitance of 305.5 F g-1 at 1 A g-1, and good cyclic stability of 98.5% retention after 10,000 consecutive charge-discharge cycles at 10 A g-1. This study provided an efficient approach for preparing graphene aerogels exhibiting hierarchical porosity for gas adsorption and supercapacitors.