Spontaneous Formation of Ultrasmall Noble Metal Nanoparticles on Cobalt-Based Layered Double Hydroxide for Electrochemical and Environmental Catalysis.

Supported noble metal nanoparticles (NMNPs) are appealing for energy and environment catalysis. To facilitate the loading of NMNPs, in situ reduction of Mn+ on the support with extra reductants/surfactants is adopted, but typically results in aggregated NMNPs with uneven size distributions or blocked active sites of the NMNPs. Herein, the use of cobalt layered double hydroxide (Co-LDH) is proposed as both support and reductant for the preparation of supported NMNPs with ultrasmall sizes and even distributions. The resultant Co-LDH-supported NMNPs exhibit excellent catalytic performance and stability. For example, Ir/Co-LDH displays a low overpotential of 188 mV (10 mA cm-2) for electrocatalytic oxygen evolution reaction and a long-term stability over 100 h (100 mA cm-2) in overall water splitting. Ru/Co-LDH can achieve a 4-nitrophenol reduction with high rate of 0.36 min-1 and S2- detection with low limit of detection (LOD) of 0.34 µm. Overall, this work provides a green and effective strategy to fabricate supported NMNPs with greatly improved catalytic performances.

Multicolor ultralong phosphorescence from perovskite-like octahedral α-AlF3.

Designing organic fluorescent and phosphorescent materials based on various core fluorophore has gained great attention, but it is unclear whether similar luminescent units exist for inorganic materials. Inspired by the BX6 octahedral structure of luminescent metal halide perovskites (MHP), here we propose that the BX6 octahedron may be a core structure for luminescent inorganic materials. In this regard, excitation-dependent color-tunable phosphorescence is discovered from α-AlF3 featuring AlF6 octahedron. Through further exploration of the BX6 unit by altering the dimension and changing the center metal (B) and ligand (X), luminescence from KAlF4, (NH4)3AlF6, AlCl3, Al(OH)3, Ga2O3, InCl3, and CdCl2 are also discovered. The phosphorescence of α-AlF3 can be ascribed to clusterization-triggered emission, i.e., weak through space interaction of the n electrons of F atoms bring close proximity in the AlF6 octahedra (inter/intra). These discoveries will deepen the understanding and contribute to further development of BX6 octahedron-based luminescent materials.

Color-tunable ultralong room temperature phosphorescence from EDTA.

Unexpected color-tunable ultralong room-temperature phosphorescence (RTP, τ∼0.5 s) was observed from EDTA (and also EDTA salts, chelates, and structural analogues). Through both experimental and theoretical investigations, the through-space conjugation of the lone pair n electrons of N/O atoms in EDTA was identified as the origin of RTP. The results here will be important for further developing phosphors with ultralong emission lifetime.

Ultralong Room-Temperature Phosphorescence from Boric Acid.

For a long time, phosphors with long-lived emission are dominated by rare earth/transition metal ion-doped sulfides and oxides. Recently, organic materials capable of emitting long-lived room-temperature phosphorescence (RTP) are reported, carbon skeletons are almost the exclusive structural feature of the conjugated luminophores. Herein, we reported that boric acid, a non-metal and C-free material, could emit RTP with lifetime up to 0.3 s. Detailed investigations indicated the weak conjugation between the n electrons of the O atoms in the B-O confined space was the possible origin of RTP. Similar RTP was also found in electron-rich N/F systems, namely, BN and BF3 (BF4 - ). Importantly, the vacant p z 0 orbital of B was found to contribute to the relevant unoccupied molecular orbitals involved in excitation, which is different from previous reports on phosphorescence from arylboronic acids. The results confirm the unique role of B as a versatile structure motif for construction of new RTP materials.

Cathodized copper porphyrin metal-organic framework nanosheets for selective formate and acetate production from CO2 electroreduction.

An efficient and selective Cu catalyst for CO2 electroreduction is highly desirable since current catalysts suffer from poor selectivity towards a series of products, such as alkenes, alcohols, and carboxylic acids. Here, we used copper(ii) paddle wheel cluster-based porphyrinic metal-organic framework (MOF) nanosheets for electrocatalytic CO2 reduction and compared them with CuO, Cu2O, Cu, a porphyrin-Cu(ii) complex and a CuO/complex composite. Among them, the cathodized Cu-MOF nanosheets exhibit significant activity for formate production with a faradaic efficiency (FE) of 68.4% at a potential of -1.55 V versus Ag/Ag+. Moreover, the C-C coupling product acetate is generated from the same catalyst together with formate at a wide voltage range of -1.40 V to -1.65 V with the total liquid product FE from 38.8% to 85.2%. High selectivity and activity are closely related to the cathodized restructuring of Cu-MOF nanosheets. With the combination of X-ray diffraction, X-ray photoelectron spectroscopy, high resolution transmission electron microscopy and Fourier transform infrared spectroscopy, we find that Cu(ii) carboxylate nodes possibly change to CuO, Cu2O and Cu4O3, which significantly catalyze CO2 to formate and acetate with synergistic enhancement from the porphyrin-Cu(ii) complex. This intriguing phenomenon provides a new opportunity for the rational design of high-performance Cu catalysts from pre-designed MOFs.