Search

To fully achieve an eco-friendly means of storing electricity in the form of chemical fuels, the development of a green synthetic route to highly active oxygen evolution reaction (OER) electrocatalysts is required. In this work, imidazolate-induced production of cobalt layered double hydroxide (Co-LDH) electrocatalysts with different assembled structures is presented. Porous Co-LDHs exhibit a remarkable OER catalytic performance with a low overpotential of η10 = 312 mV, while cage-like Co-LDHs prepared by the transformation of ZIF-67 show a slightly inferior performance. Such a phenomenon is attributed to the assembled structure difference, giving rise to a difference in electron transfer and mass transport as well as the number of accessible active sites. After disassembly, these disperse Co-LDH sheets give a similar catalytic performance (η10: 288–290 mV) due to bearing similar components. Importantly, the reversible/cycling transformation between Co-LDHs and ZIF-67 provides an effective method to radically reduce pollutant release and resource consumption, from the point of view of material synthesis. [ABSTRACT FROM AUTHOR]

The preparation of carbon dots (CDs) featuring almost the same structures in different solvents is beneficial for their direct applications in the desired media without additional treatment and for resource conservation. The structures of CDs, however, are vulnerable to the synthetic system, unfavorably forming “identical” CDs in different solvents. Herein, we developed a top-down method to explore the feasibility of preparing similar CDs from ZIF-8-derived solid porous carbons that comprising graphitic carbon embedded into the amorphous carbon domains in water, amide and alcohol. To attenuate the solvent effect, the porous carbon was oxidized by nitric acid prior to solvothermal/hydrothermal treatment. The use of oxidized porous carbon as precursors can result in the formation of CDs using a mild thermal treatment. Other than CDs prepared in amide (in DMF, CDs-d), the resulting CDs prepared in water (CDs-w) and in alcohol (in methanol, CDs-m) possess similar components and structures, as confirmed by XPS and DLS. Thus, both CDs-w and CDs-m aqueous suspensions exhibit excitation wavelength-dependent PL properties with the same emission maxima. CDs-w was directly applied in aqueous systems and gave slightly enhanced performance in cellular imaging and solar hydrogen evolution. Significantly, this research offers an available strategy to advance CD performance and reduce pollutant emission. [ABSTRACT FROM AUTHOR]

The change of atom density induced structural collapse in the transformation process from metal-organic frameworks (MOFs) to their inorganic counterparts is a major challenge to the achievement of porous hollow structures. Herein, we develop an amino acid-mediated strategy for transformation of NH 2 -MIL-125(Ti) to successfully synthesize well-defined porous cages of titanium oxides (PCT) due to sheets serving as structural scaffolds. On this basis, PCT supported Pt-based nanoparticles are generated via a similar synthetic route, and are utilized to study the selective hydrogenation of carbonyl groups in α,β-unsaturated aldehydes, benefiting from the specific structures of PCT and tunable electronic structures of Pt mainly affected by doping with metal species such as Co. In this case, Pt-Co/PCT composites give 96% selectivity for cinnamyl alcohol at 100% conversion of cinnamaldehyde under 0.2 MPa H 2 and 80 °C for 3 h. This research would offer a promising strategy for important organic transformations in academic and industrial research to selectively synthesize high-value-added products.