• Construction of C-C bonds via photoreductive coupling of ketones and aldehydes in the metal-organic-framework MFM-300(Cr)

      Luo, Tian; Li, Lili; Chen, Yinlin; orcid: 0000-0001-7878-2063; An, Jie; email: jie_an@cau.edu.cn; Liu, Chengcheng; Yan, Zheng; Carter, Joseph H.; orcid: 0000-0001-5530-7390; Han, Xue; Sheveleva, Alena M.; Tuna, Floriana; orcid: 0000-0002-5541-1750; et al. (Nature Publishing Group UK, 2021-06-11)
      Abstract: Construction of C-C bonds via reductive coupling of aldehydes and ketones is hindered by the highly negative reduction potential of these carbonyl substrates, particularly ketones, and this renders the formation of ketyl radicals extremely endergonic. Here, we report the efficient activation of carbonyl compounds by the formation of specific host-guest interactions in a hydroxyl-decorated porous photocatalyst. MFM-300(Cr) exhibits a band gap of 1.75 eV and shows excellent catalytic activity and stability towards the photoreductive coupling of 30 different aldehydes and ketones to the corresponding 1,2-diols at room temperature. Synchrotron X-ray diffraction and electron paramagnetic resonance spectroscopy confirm the generation of ketyl radicals via confinement within MFM-300(Cr). This protocol removes simultaneously the need for a precious metal-based photocatalyst or for amine-based sacrificial agents for the photochemical synthesis.
    • Giant magneto-birefringence effect and tuneable colouration of 2D crystal suspensions

      Ding, Baofu; orcid: 0000-0001-6646-7285; Kuang, Wenjun; orcid: 0000-0003-4309-365X; Pan, Yikun; Grigorieva, I. V.; orcid: 0000-0001-5991-7778; Geim, A. K.; orcid: 0000-0003-2861-8331; email: geim@manchester.ac.uk; Liu, Bilu; orcid: 0000-0002-7274-5752; email: bilu.liu@sz.tsinghua.edu.cn; Cheng, Hui-Ming; orcid: 0000-0002-5387-4241; email: hmcheng@sz.tsinghua.edu.cn (Nature Publishing Group UK, 2020-07-24)
      Abstract: One of the long-sought-after goals in light manipulation is tuning of transmitted interference colours. Previous approaches toward this goal include material chirality, strain and electric-field controls. Alternatively, colour control by magnetic field offers contactless, non-invasive and energy-free advantages but has remained elusive due to feeble magneto-birefringence in conventional transparent media. Here we demonstrate an anomalously large magneto-birefringence effect in transparent suspensions of magnetic two-dimensional crystals, which arises from a combination of a large Cotton-Mouton coefficient and relatively high magnetic saturation birefringence. The effect is orders of magnitude stronger than those previously demonstrated for transparent materials. The transmitted colours of the suspension can be continuously tuned over two-wavelength cycles by moderate magnetic fields below 0.8 T. The work opens a new avenue to tune transmitted colours, and can be further extended to other systems with artificially engineered magnetic birefringence.
    • In-situ nanospectroscopic imaging of plasmon-induced two-dimensional [4+4]-cycloaddition polymerization on Au(111)

      Shao, Feng; orcid: 0000-0003-3879-5884; email: feng.shao@manchester.ac.uk; Wang, Wei; Yang, Weimin; Yang, Zhilin; Zhang, Yao; orcid: 0000-0002-6524-0289; Lan, Jinggang; email: jinggang.lan@chem.uzh.ch; Dieter Schlüter, A.; Zenobi, Renato; orcid: 0000-0001-5211-4358; email: zenobi@org.chem.ethz.ch (Nature Publishing Group UK, 2021-07-27)
      Abstract: Plasmon-induced chemical reactions (PICRs) have recently become promising approaches for highly efficient light-chemical energy conversion. However, an in-depth understanding of their mechanisms at the nanoscale still remains challenging. Here, we present an in-situ investigation by tip-enhanced Raman spectroscopy (TERS) imaging of the plasmon-induced [4+4]-cycloaddition polymerization within anthracene-based monomer monolayers physisorbed on Au(111), and complement the experimental results with density functional theory (DFT) calculations. This two-dimensional (2D) polymerization can be flexibly triggered and manipulated by the hot carriers, and be monitored simultaneously by TERS in real time and space. TERS imaging provides direct evidence for covalent bond formation with ca. 3.7 nm spatial resolution under ambient conditions. Combined with DFT calculations, the TERS results demonstrate that the lateral polymerization on Au(111) occurs by a hot electron tunneling mechanism, and crosslinks form via a self-stimulating growth mechanism. We show that TERS is promising to be plasmon-induced nanolithography for organic 2D materials.
    • Laser solid-phase synthesis of single-atom catalysts

      Peng, Yudong; Cao, Jianyun; Sha, Yang; Yang, Wenji; Li, Lin; Liu, Zhu; email: zhu.liu@manchester.ac.uk (Nature Publishing Group UK, 2021-08-18)
      Abstract: Single-atom catalysts (SACs) with atomically dispersed catalytic sites have shown outstanding catalytic performance in a variety of reactions. However, the development of facile and high-yield techniques for the fabrication of SACs remains challenging. In this paper, we report a laser-induced solid-phase strategy for the synthesis of Pt SACs on graphene support. Simply by rapid laser scanning/irradiation of a freeze-dried electrochemical graphene oxide (EGO) film loaded with chloroplatinic acid (H2PtCl6), we enabled simultaneous pyrolysis of H2PtCl6 into SACs and reduction/graphitization of EGO into graphene. The rapid freezing of EGO hydrogel film infused with H2PtCl6 solution in liquid nitrogen and the subsequent ice sublimation by freeze-drying were essential to achieve the atomically dispersed Pt. Nanosecond pulsed infrared (IR; 1064 nm) and picosecond pulsed ultraviolet (UV; 355 nm) lasers were used to investigate the effects of laser wavelength and pulse duration on the SACs formation mechanism. The atomically dispersed Pt on graphene support exhibited a small overpotential of −42.3 mV at −10 mA cm−2 for hydrogen evolution reaction and a mass activity tenfold higher than that of the commercial Pt/C catalyst. This method is simple, fast and potentially versatile, and scalable for the mass production of SACs.
    • Mineral reaction kinetics constrain the length scale of rock matrix diffusion

      Wogelius, R. A.; orcid: 0000-0002-5781-2152; email: roy.wogelius@manchester.ac.uk; Milodowski, A. E.; Field, L. P.; orcid: 0000-0002-8747-9901; Metcalfe, R.; Lowe, T.; van Veelen, A.; orcid: 0000-0002-8176-3645; Carpenter, G.; Norris, S.; Yardley, B. (Nature Publishing Group UK, 2020-05-18)
      Abstract: Mass transport by aqueous fluids is a dynamic process in shallow crustal systems, redistributing nutrients as well as contaminants. Rock matrix diffusion into fractures (void space) within crystalline rock has been postulated to play an important role in the transient storage of solutes. The reacted volume of host rock involved, however, will be controlled by fluid-rock reactions. Here we present the results of a study which focusses on defining the length scale over which rock matrix diffusion operates within crystalline rock over timescales that are relevant to safety assessment of radioactive and other long-lived wastes. Through detailed chemical and structural analysis of natural specimens sampled at depth from an active system (Toki Granite, Japan), we show that, contrary to commonly proposed models, the length scale of rock matrix diffusion may be extremely small, on the order of centimetres, even over timescales of millions of years. This implies that in many cases the importance of rock matrix diffusion will be minimal. Additional analyses of a contrasting crystalline rock system (Carnmenellis Granite, UK) corroborate these results.
    • Mixing between chemically variable primitive basalts creates and modifies crystal cargoes

      Neave, David A.; orcid: 0000-0001-6343-2482; email: david.neave@manchester.ac.uk; Beckmann, Philipp; Behrens, Harald; Holtz, François (Nature Publishing Group UK, 2021-09-17)
      Abstract: Basaltic crystal cargoes often preserve records of mantle-derived chemical variability that have been erased from their carrier liquids by magma mixing. However, the consequences of mixing between similarly primitive but otherwise chemically variable magmas remain poorly understood despite ubiquitous evidence of chemical variability in primary melt compositions and mixing-induced disequilibrium within erupted crystal cargoes. Here we report observations from magma–magma reaction experiments performed on analogues of primitive Icelandic lavas derived from distinct mantle sources to determine how their crystal cargoes respond to mixing-induced chemical disequilibrium. Chemical variability in our experimental products is controlled dominantly by major element diffusion in the melt that alters phase equilibria and triggers plagioclase resorption within regions that were initially plagioclase saturated. Isothermal mixing between chemically variable basaltic magmas may therefore play important but previously underappreciated roles in creating and modifying crystal cargoes by unlocking plagioclase-rich mushes and driving resorption, (re-)crystallisation and solid-state diffusion.
    • Refinement of pore size at sub-angstrom precision in robust metal–organic frameworks for separation of xylenes

      Li, Xiaolin; Wang, Juehua; Bai, Nannan; Zhang, Xinran; orcid: 0000-0002-0734-6173; Han, Xue; da Silva, Ivan; orcid: 0000-0002-4472-9675; Morris, Christopher G.; Xu, Shaojun; orcid: 0000-0002-8026-8714; Wilary, Damian M.; Sun, Yinyong; orcid: 0000-0002-5570-5089; et al. (Nature Publishing Group UK, 2020-08-27)
      Abstract: The demand for xylenes is projected to increase over the coming decades. The separation of xylene isomers, particularly p- and m-xylenes, is vital for the production of numerous polymers and materials. However, current state-of-the-art separation is based upon fractional crystallisation at 220 K which is highly energy intensive. Here, we report the discrimination of xylene isomers via refinement of the pore size in a series of porous metal–organic frameworks, MFM-300, at sub-angstrom precision leading to the optimal kinetic separation of all three xylene isomers at room temperature. The exceptional performance of MFM-300 for xylene separation is confirmed by dynamic ternary breakthrough experiments. In-depth structural and vibrational investigations using synchrotron X-ray diffraction and terahertz spectroscopy define the underlying host–guest interactions that give rise to the observed selectivity (p-xylene < o-xylene < m-xylene) and separation factors of 4.6–18 for p- and m-xylenes.
    • Water friction in nanofluidic channels made from two-dimensional crystals

      Keerthi, Ashok; Goutham, Solleti; You, Yi; Iamprasertkun, Pawin; orcid: 0000-0001-8950-3330; Dryfe, Robert A. W.; orcid: 0000-0002-9335-4451; Geim, Andre K.; orcid: 0000-0003-2861-8331; Radha, Boya; orcid: 0000-0003-1345-7029; email: radha.boya@manchester.ac.uk (Nature Publishing Group UK, 2021-05-25)
      Abstract: Membrane-based applications such as osmotic power generation, desalination and molecular separation would benefit from decreasing water friction in nanoscale channels. However, mechanisms that allow fast water flows are not fully understood yet. Here we report angstrom-scale capillaries made from atomically flat crystals and study the effect of confining walls’ material on water friction. A massive difference is observed between channels made from isostructural graphite and hexagonal boron nitride, which is attributed to different electrostatic and chemical interactions at the solid-liquid interface. Using precision microgravimetry and ion streaming measurements, we evaluate the slip length, a measure of water friction, and investigate its possible links with electrical conductivity, wettability, surface charge and polarity of the confining walls. We also show that water friction can be controlled using hybrid capillaries with different slip lengths at opposing walls. The reported advances extend nanofluidics’ toolkit for designing smart membranes and mimicking manifold machinery of biological channels.