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Carbon-carbon coupling is a basic design principle for the synthesis of porous organic polymers, which are widely used in gas adsorption/separation, photocatalysis, energy storage, etc. However, the C(sp 3 )-C(sp 3 ) coupling reaction to construct porous organic polymers remains an important yet elusive objective due to its low reactivity and unknown side reactions. Herein, we report that nickel bis(1,5-cyclooctadiene) (Ni(COD) 2 ), which was a famous catalyst for C(sp 2 )-C(sp 2 ) coupling reactions, enables highly efficient C(sp 3 )-C(sp 3 ) homo-coupling reactions to construct porous linear crystalline polymers and flexible three-dimensional porous aromatic frameworks (PAFs) under mild reaction conditions. The resulting linear polymers generated with dibromomethyl arenes have good crystallinity and high melting points ( T m = 286 °C) due to controllability of reaction sites. Furthermore, the PAFs (PAF-64, PAF-65 and PAF-66) stemmed from tri-/tetra-bromomethyl arenes show high surface area ( S BET = 390 m 2 g -1 ) and high methane-storage capacity (up to 313 cm 3 cm -3 ) because of their flexible frameworks. This work sheds new light on the construction of novel porous polymers through C(sp 3 )-C(sp 3 ) coupling reactions and the development of methane-storage materials., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Vibrational coherence has attracted considerable research interests because of its potential functions in light harvesting systems. Although positive signs of vibrational coherence in metal nanoclusters have been observed, the underlying mechanism remains to be verified. Here, we demonstrate that robust vibrational coherence with a lifetime of 1 ps can be clearly identified in Ag 44 (SR) 30 core-shell nanoclusters, in which an icosahedral Ag 12 core is well protected by a dodecahedral Ag 20 cage. Ultrafast spectroscopy reveals that two vibrational modes at around 2.4 THz and 1.6 THz, corresponding to the breathing mode and quadrupolar-like mode of the icosahedral Ag 12 core, respectively, are responsible for the generation of vibrational coherence. In addition, the vibrational coherence of Ag 44 has an additional high frequency mode (2.4 THz) when compared with that of Ag 29 , in which there is only one low frequency vibration mode (1.6 THz), and the relatively faster dephasing in two-layer Ag 29 relative to that in Ag 44 further supports the fact that the robust vibrational coherence in Ag 44 is ascribed to its unique matryoshka-like core-shell structure. Our findings not only present unambiguous experimental evidence for a multi-layer core-shell structure protected vibrational coherence under ambient conditions but also offers a practical strategy for the design of highly efficient quantum optoelectronic devices., Competing Interests: The authors declare no conflicts of interest., (This journal is © The Royal Society of Chemistry.)

Recently, a MoSi 2 N 4 monolayer has been successfully synthesized by a delicately designed chemical vapor deposition (CVD) method. It exhibits promising (opto)electronic properties due to a relatively narrow bandgap (∼1.94 eV), high electron/hole mobility, and excellent thermal/chemical stability. Currently, much effort is being devoted to further improving its properties through engineering defects or constructing nanocomposites ( e.g. , van der Waals heterostructures). Herein, we report a theoretical investigation on hydrogenation as an alternative surface functionalization approach to effectively manipulate its electronic structures and optical properties. The calculation results suggested that chemisorption of H atoms on the top of N atoms on MoSi 2 N 4 was energetically most favored. Upon H chemisorption, the band gap values gradually decreased from 1.89 eV (for intrinsic MoSi 2 N 4 ) to 0 eV (for MoSi 2 N 4 -16H) and 0.25 eV (for MoSi 2 N 4 -32H), respectively. The results of optical properties studies revealed that a noticeable enhancement in light absorption intensity could be realized in the visible light range after the surface hydrogenation process. Specifically, full-hydrogenated MoSi 2 N 4 (MoSi 2 N 4 -32H) manifested a higher absorption coefficient than that of semi-hydrogenated MoSi 2 N 4 (MoSi 2 N 4 -16H) in the visible light range. This work can provide theoretical guidance for rational engineering of optical and optoelectronic properties of MoSi 2 N 4 monolayer materials via surface hydrogenation towards emerging applications in electronics, optoelectronics, photocatalysis, etc., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

The coherent vibrational dynamics of gold nanoclusters (NCs) provides important information on the coupling between vibrations and electrons as well as their mechanical properties, which is critical for understanding the evolution from a metallic state to a molecular state with diminishing size. Coherent vibrations have been widely explored in small-sized atomically precise gold NCs, while it remains a challenge to observe them in large-sized gold NCs. In this work, we report the coherent vibrational dynamics of atomically precise Au 144 (SR) 60 NCs via temperature-dependent femtosecond transient absorption (TA) spectroscopy. The population dynamics of Au 144 (SR) 60 consists of three relaxation processes: internal conversion, core-shell charge transfer and relaxation to the ground state. After removing the population dynamics from the TA kinetics, fast Fourier transform analysis on the residual oscillation reveals distinct vibrational modes at 1.5 THz (50 cm -1 ) and 2 THz (67 cm -1 ), which arise from the wavepacket motions along the ground-state and excited-state potential energy surfaces (PES), respectively. These results are helpful for understanding the physical properties of gold nanostructures with a threshold size that lies in between those of molecular-like NCs and metallic-state nanoparticles., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Color-tunable ultralong phosphorescence is urgently desired in optoelectronic applications. Herein, we report a new type of full-color-tunable ultralong phosphorescence carbon dots (CDs) without matrix-assistance by a self-doping method under ambient conditions. The phosphorescence color can be rationally tuned from blue to red by changing the excitation wavelength from 310 to 440 nm. The CDs exhibit an ultralong lifetime of up to 1052.23 ms at 484 nm. From the experimental data, we speculate that the excitation-dependent multi-color phosphorescence is attributed to the presence of multiple emitting centers related to carbonyl units. Given the unique color-tunability of CDs, we demonstrate their potential applications in information encryption, light detection ranging from UV to visible light and LED devices. This finding not only takes a step towards the fundamental design of full-color emissive materials, but also provides a broader scope for the applications of phosphorescent materials., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Peroxisome proliferator-activated receptor gamma (PPAR γ ) is an attractive target for chemoprevention of lung carcinoma, however its highly dynamic nature has plagued drug development for decades, with difficulties in receptor modeling for structure-based design. In this work, an integrated receptor-based virtual screening (VS) strategy was applied to identify PPAR γ agonists as chemoprophylactic agents by using extensive docking and conformational sampling methods. Our results showed that the conformational plasticity of PPAR γ , especially the H2 & S245 loop, H2' & Ω loop and AF-2 surface, is markedly affected by binding of full/partial agonists. To fully take the dynamic behavior of PPAR γ into account, the VS approach effectively sorts out five commercial agents with reported antineoplastic properties. Among them, ZINC03775146 (gusperimus) and ZINC14087743 (miltefosine) might be novel PPAR γ agonists with the potential for chemoprophylaxis, that simultaneously take part in a flexible switch of the AF-2 surface and state change of the Ω loop. Furthermore, the dynamic structural coupling between the H2 & S245 and H2' & Ω loops offers enticing hope for PPAR γ -targeted therapeutics, by blocking kinase accessibility to PPAR γ . These results might aid the development of chemopreventive drugs, and the integrated VS strategy could be conducive to drug design for highly flexible biomacromolecules., Competing Interests: The authors have declared that no competing interests exist., (This journal is © The Royal Society of Chemistry.)

The catalytic reduction of NO with NH 3 (NH 3 -SCR) on phosphorus-doped carbon aerogels (P-CAs) was studied in the temperature range of 100-200 °C. The P-CAs were prepared by a one-pot sol-gel method by using phosphoric acid as a phosphorus source followed by carbonization at 600-900 °C. A correlation between catalytic activity and surface P content is observed. The P-CA-800 vac sample obtained via carbonization at 800 °C and vacuum treatment at 380 °C shows the highest NO conversion of 45.6-76.8% at 100-200 °C under a gas hourly space velocity of 500 h -1 for the inlet gas mixture of 500 ppm NO, 500 ppm NH 3 and 5.0 vol% O 2 . The coexistence of NH 3 and O 2 is essential for the high conversion of NO on the P-CA carbon catalysts, which can decrease the spillover of NO 2 and N 2 O. The main Brønsted acid sites derived from P-doping and contributed by the C-OH group at edges of carbon sheets are beneficial for NH 3 adsorption. In addition, the C 3 -P[double bond, length as m-dash]O configuration seems to have the most active sites for favorable adsorption and dissociation of O 2 and facilitates the formation of NO 2 . Therefore, the simultaneous presence of acidic groups for NH 3 adsorption and the C 3 -P[double bond, length as m-dash]O active sites for NO 2 generation due to the activation of O 2 molecules is likely responsible for the significant increase in the NH 3 -SCR activity over the P-CAs. The transformation of C 3 -P[double bond, length as m-dash]O to C-O-P functional groups after the reaction is found, which could be assigned to the oxidation of C 3 -P[double bond, length as m-dash]O by the dissociated O*, resulting in an apparent decrease of catalytic activity for P-CAs. The C-O-P based functional groups are also active in the NH 3 -SCR reaction., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Traps, size and aqueous-dispersibility are the most important parameters that affect the features and applications of persistent luminescent nanoparticles (PLNPs). However, simultaneous controlling of these parameters is rather difficult and has not been reported yet. We present the first exploration on adjusting the traps, size and aqueous-dispersibility of PLNPs via simple ethylenediaminetetraacetate (EDTA) etching. Cr 0.004 3+ :ZnGa 2 O 4 (ZGO) was used as the PLNP model. EDTA etching of the sintered ZGO results in effective reduction of the size and great improvement in the aqueous-dispersibility. In addition, EDTA etching alters the density of mediate traps and generates new deep traps, thus achieving the massive production of (ultra)small ZGO-EDTA with fine aqueous-dispersibility, suitable mediate/deep traps and superlong bright afterglows (51 days). As EDTA can interact with most metals, this simple EDTA etching strategy is prospectively amenable to other PLNPs, and the resulting PLNPs-EDTA have wide applications in both biological field and information storage.

To achieve a high power density of lithium-ion batteries, it is essential to develop anode materials with high capacity and excellent stability. Cobalt oxide (Co 3 O 4 ) is a prospective anode material on account of its high energy density. However, the poor electrical conductivity and volumetric changes of the active material induce a dramatic decrease in capacity during cycling. Herein, a hierarchical porous hybrid nanofiber of ZIF-derived Co 3 O 4 and continuous carbon nanofibers (CNFs) is rationally constructed and utilized as an anode material for lithium-ion batteries. The PAN/ZIF-67 heterostructure composite nanofibers were first synthesized using electrospinning technology followed by the in situ growth method, and then the CNFs/Co 3 O 4 nanofibers were obtained by subsequent multi-step thermal treatment. The continuous porous conductive carbon backbone not only effectively provides a channel to expedite lithium ion diffusion and electrode transfer, but also accommodates volume change of Co 3 O 4 during the charge-discharge cycling process. The electrode exhibits a high discharge capacity of 1352 mA h g -1 after 500 cycles at a constant current density of 0.2 A g -1 . Additionally, the composites deliver a discharge capacity of 661 mA h g -1 with a small capacity decay of 0.078% per cycle at a high current density of 2 A g -1 after 500 cycles. This hierarchical porous structural design presents an effective strategy to develop a hybrid nanofiber for improving lithium ion storage., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Cost-effective and efficient electrocatalysts for the oxygen reduction reaction (ORR) are crucial for fuel cells and metal-air batteries. Herein, we report the facile synthesis of a Co/CoO/Co 3 O 4 heterostructure embedded in a porous carbon matrix by refluxing and annealing. This composite exhibits several structural merits for catalyzing the ORR: (1) the existence of metallic Co and graphitic carbon enhanced the electrical conduction; (2) the porous, loose carbon network facilitated the electrolyte permeation and mass transport; (3) more importantly, the nanosized coherent CoO/Co 3 O 4 heterojunctions with structural defects and oxygen vacancies enhanced the charge transport/separation at the interface and adsorption affinity to O 2 , thus promoting the ORR kinetics and lowering the reaction barrier. Consequently, the composite electrode manifests high electrocatalytic activity, attaining a current density of 6.7 mA cm -2 at -0.8 V ( vs. Ag/AgCl), which is superior to pure CoO nanoparticles (4.7 mA cm -2 ), and has good methanol tolerance. The present strategy based on heterostructure and vacancy engineering may pave the way for the exploration of more advanced, low-cost electrocatalysts for electrochemical reduction and evolution processes., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)