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The exploitation of hierarchical carbon nanocages with superior light-to-heat conversion efficiency, together with their distinct structural, morphological, and electronic properties, in photothermal applications could provide effective solutions to long-standing challenges in diverse areas. Here, we demonstrate the discovery of pristine and nitrogen-doped hierarchical carbon nanocages as superior supports for highly loaded, small-sized Ru particles toward enhanced photothermal CO 2 catalysis. A record CO production rate of 3.1 mol·g Ru -1 ·h -1 with above 90% selectivity in flow reactors was reached for hierarchical nitrogen-doped carbon-nanocage-supported Ru clusters under 2.4 W·cm -2 illumination without external heating. Detailed studies reveal that the enhanced performance originates from the strong broadband sunlight absorption and efficient light-to-heat conversion of nanocage supports as well as the excellent intrinsic catalytic reactivity of sub-2 nm Ru particles. Our study reveals the great potential of hierarchical carbon nanocages in photothermal catalysis to reduce the fossil fuel consumption of various industrial chemical processes and stimulates interest in their exploitation for other demanding photothermal applications.

Driving metal-cluster-catalyzed high-temperature chemical reactions by sunlight holds promise for the development of negative-carbon-footprint industrial catalysis, which has yet often been hindered by the poor ability of metal clusters to harvest and utilize the full spectrum of solar energy. Here, we report the preparation of Mo 2 TiC 2 MXene-supported Ru clusters (Ru/Mo 2 TiC 2 ) with pronounced broadband sunlight absorption ability and high sintering resistance. Under illumination of focused sunlight, Ru/Mo 2 TiC 2 can catalyze the reverse water-gas shift (RWGS) reaction to produce carbon monoxide from the greenhouse gas carbon dioxide and renewable hydrogen with enhanced activity, selectivity, and stability compared to their nanoparticle counterparts. Notably, the CO production rate of MXene-supported Ru clusters reached 4.0 mol·g Ru -1 ·h -1 , which is among the best reported so far for photothermal RWGS catalysts. Detailed studies suggest that the production of methane is kinetically inhibited by the rapid desorption of CO from the surface of the Ru clusters.

The conversion of CO 2 into fuels and feedstock chemicals via photothermal catalysis holds promise for efficient solar energy utilization to tackle the global energy shortage and climate change. Despite recent advances, it is of emerging interest to explore promising materials with excellent photothermal properties to boost the performance of photothermal CO 2 catalysis. Here, we report the discovery of MXene materials as superior photothermal supports for metal nanoparticles. As a proof-of-concept study, we demonstrate that Nb 2 C and Ti 3 C 2 , two typical MXene materials, can enhance the photothermal effect and thus boost the photothermal catalytic activity of Ni nanoparticles. A record CO 2 conversion rate of 8.50 mol·g Ni -1 ·h -1 is achieved for Nb 2 C-nanosheet-supported Ni nanoparticles under intense illumination. Our study bridges the gap between photothermal MXene materials and photothermal CO 2 catalysis toward more efficient solar-to-chemical energy conversions and stimulates the interest in MXene-supported metal nanoparticles for other heterogeneous catalytic reactions, particularly driven by sunlight.

We have examined the 17 O quadrupole-central-transition (QCT) NMR signal from [ 17 O]nicotinamide (vitamin B3) dissolved in glycerol. Measurements were performed at five magnetic fields ranging from 9.4 to 35.2 T between 243 and 363 K. We found that, in the ultraslow motion regime, cross-correlation between the second-order quadrupole interaction and magnetic shielding anisotropy is an important contributor to the transverse relaxation process for the 17 O QCT signal of [ 17 O]nicotinamide. While such a cross-correlation effect has generally been predicted by relaxation theory, we report here the first experimental evidence for this phenomenon in solution-state NMR for quadrupolar nuclei. We have discussed the various factors that determine the ultimate resolution limit in QCT NMR spectroscopy. The present study also highlights the advantages of performing QCT NMR experiments at very high magnetic fields (e.g., 35.2 T).

We report variable-temperature (VT) (17)O NMR spectra of [5-(17)O]-d-glucose in an aqueous solution and in glycerol at 14.1 and 21.1 T. The VT (17)O NMR data cover a wide range of motion for which the molecular rotational correlation time (τc) of glucose changes more than 5 orders of magnitude. The observed line width of the (17)O NMR signal for [5-(17)O]-d-glucose displays a maximum at ω0τc ≈ 1 and a minimum at ω0τc ≈ 150, where ω0 is the angular Larmor frequency of (17)O. Under the ultraslow motion condition (i.e., ω0τc > 150), the line width of the observed (17)O NMR signal increases drastically with τc, suggesting that the second-order quadrupolar interaction becomes the predominant relaxation mechanism. While this relaxation mechanism has long been predicted by theory, the current study reports the first experimental observation of such a phenomenon. The implications of this new relaxation mechanism on the spectral resolution limit in liquid-state NMR spectroscopy for half-integer spins are discussed.