Platinum was coated on the surfaces of copper nanocubes to form Cu−CuPt core−alloy−frame nanocrystals with a rhombic dodecahedral (RD) shape. Co-reduction of Pt 2+ ions and residual Cu + ions in the supernatant of the Cu nanocube solution followed by the interdiffusion of Cu and Pt atoms over the core−shell interface allowed their formation. Growth in the ⟨100⟩ directions of the {100}-terminated Cu nanocubes resulted in the {110}-faceted rhombic dodecahedra. By the introduction of additional Pt precursor, the {100} vertices of the Cu−CuPt RD nanocrystals could be selectively extended to form spiny CuPt RD nanocrystals. After removing the Cu core template, both CuPt alloy RD and spiny CuPt alloy RD nanoframes (NFs) were obtained with Pt/Cu ratios of 26/ 74 and 41/59, respectively. Abundant surface defects render them highly active catalysts due to the open frame structure of both sets of NFs. The spiny RD NFs showed superior specific activity toward the oxygen reduction reaction, 1.3 and 3 times to those of the RD NFs and the commercial Pt/C catalysts, respectively. In 4-nitrophenol reduction, both NFs displayed better activity compared to commercial Pt NPs in the dark. Their activities were improved ∼1.3 times under irradiation of visible light, attributed to the effect of LSPR enhancement by the Cu-rich skeleton.
The creation of hierarchical porosity in metal-organic frameworks (MOFs) could benefit various applications of MOFs such as gas storage and separation. Having single-crystalline microcrystals instead of poly-crystalline composites is critical for these potential applications of MOFs with hierarchical porosity. We developed a room temperature synthetic method to generate uniform hollow and mesoporous zeolitic imidazolate framework-8 (ZIF-8) microcrystals with a single-crystalline structure via overgrowing a ZIF-8 shell in methanol solution on a ZIF-8 core with water adsorbed in the pores. The cavities formed as a result of the different solvent micro-environment. This double-solvent mediated overgrowth method could be applied to prepare other MOFs with hierarchical porosity.
Materials with non-linear optical (NLO) properties play an important role in the construction of electronic devices for optical communications, optical data processing and data storage. With this aim in mind, a Zn(II)-based metal-organic framework {[Zn2(nica)2(bpy)1.5(H2O)]⋅0.5(bpy)⋅3H2O}n (1), was synthesized using 4,4ʹ-bipyridine (bpy) and a potentially bidentate ligand, 2-hydroxynicotinic acid (H2nica) with a salicylate binding moiety. A single-crystal X-ray diffraction analysis revealed that compound 1 crystallized in the orthorhombic space group Fdd2 and was composed of a three dimensional porous framework. Since Fdd2 belonged to a class of non-centrosymmetric space groups, we therefore investigated the non-linear optical behaviour of compound 1. Photoluminescence studies revealed that compound 1 exhibited a blue light emission with a maxima at 457 nm.
An SHG-active framework of 1-Zn can undergo metal metathesis, in which the tetrahedrally coordinated Zn(ii) ions are completely exchanged with Cu(ii) ions while retaining the integrity of the network.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.