Materials Data on Rh(CO)3 by Materials Project
Rh(CO)3 crystallizes in the monoclinic P2_1/c space group. The structure is zero-dimensional and consists of forty-eight formaldehyde molecules and sixteen rhodium molecules.
36 MATERIALS SCIENCE↗
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A Principle for Highly Active Metal Oxide Catalysts via NaCl-Based Solid Solution
Toward the preparation of industrial metal oxide catalysts, sacrificial organic templates, excessive solvents, complex impregnation, and drying steps are generally required. Here, we report a versatile rule for the simple synthesis of highly porous metal oxides with well-dispersed noble metal species. Porous metal oxides (Co 3 O 4 , Fe x O y , and Cr 2 O 3 ) are obtained with some surface areas (e.g., Cr 2 O3: 224 m 2 ·g -1 ) beyond the record value. Surprisingly, small noble metal nanoparticles (e.g., Pd: 3.1 and Pt: 3.2 nm) could be incorporated by this solid-state process simultaneously. Corresponding Rh-Co 3 O 4 , Pd-Fe x O y , and Pt-Cr 2 O 3 exhibit excellent performance: CH 4 combustion (T90 = ~360°C and thermal stability: >100 h at 680°C), hydrogenation of nitrobenzene and derivatives (turnover number [TON] = 2.49 × 104, 300 mmol per run), and reversed water gas shift (RWGS) reaction (44% CO 2 conversion with ~98% CO selectivity and thermal stability: >100 h at 500°C), respectively. Therefore, current principle via a NaCl-based solid solution could provide a solid-state, fast, and efficient route for processing metal oxide catalysts.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Synthesis Of Ir(1-x-y)Rh(x)Co(y)Sb(3) Semiconductors
Ir(1-x-y)Rh(x)Co(y)Sb(3) semiconductors synthesized by gradient-freeze and sintering techniques. Sintering techniques used for variety of compositions; gradient-freeze technique used for RhSb(3) and CoSb(3).
Caillat, Thierry↗
Visible Light Photolysis at Single Atom Sites in Semiconductor Perovskite Oxides
Designing catalysts with well-defined active sites with chemical functionality responsive to visible light has significant potential for overcoming scaling relations limiting chemical reactions over heterogeneous catalyst surfaces. Visible light can be leveraged to facilitate the removal of strongly bound species from well-defined single cationic sites (Rh) under mild conditions (323 K) when they are incorporated within a photoactive perovskite oxide (Rh-doped SrTiO 3 ). CO, a key intermediate in many chemistries, forms stable geminal dicarbonyl Rh complexes (Rh + (CO) 2 ), that could act as site blockers or poisons during a catalytic cycle. For the first time, we demonstrate that CO removal can occur at mild temperatures (323 K) under low-energy red light (635 nm) irradiation, which is not possible for supported isolated-site Rh catalysts (0.2 wt % Rh/γ-Al 2 O 3 ). Photolysis of supported Rh + (CO) 2 complexes (e.g., 0.2 wt % Rh/γ-Al 2 O 3 ) has been demonstrated but is limited to high energy UV photons. Rigorous kinetic experiments elucidate disparate mechanisms for CO photodepletion from Rh-doped SrTiO 3 and supported isolated site Rh/γ-Al 2 O 3 . CO photodepletion from supported isolated site Rh/γ-Al 2 O 3 involves a direct metal to ligand charge transfer mechanism, whereas Rh-doped SrTiO 3 is governed by electron–hole pair formation in the perovskite. In this work, we show that under visible, low-energy red light, surface Rh species in Rh-doped SrTiO 3 introduce midgap energy states above the valence band that facilitate electronic excitations leading to surface CO removal. Isolated Rh sites in Rh-doped SrTiO 3 also exhibit exceptional stability under multiple CO photodepletion cycles. Overall, incorporating single sites into photoactive perovskite oxides is an effective strategy to influence surface chemistries with visible light.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Controlling Reaction Pathways of Ethylene Hydroformylation Using Isolated Bimetallic Rhodium–Cobalt Sites
Designing efficient ligand-free heterogeneous catalysts for ethylene hydroformylation to produce C 3 oxygenates is of importance for both fundamental research and practical applications, but it is often hindered by insufficient catalytic activity and selectivity. Here, this work designs isolated rhodium–cobalt (Rh–Co) sites confined within a ZSM-5 zeolite to enhance ethylene hydroformylation rates and selectivity while maintaining catalyst stability. By adjusting the Co/Al ratio in Co-ZSM-5, different sizes of Co are formed; subsequent Rh introduction produces isolated Rh 1 Co x clusters with different Rh–Co coordination numbers (CNs). In-situ characterizations and density functional theory calculations reveal that a Rh–Co CN of 3, corresponding to an isolated Rh 1 Co 3 site, provides optimal bindings to reaction intermediates and thus achieves the highest hydroformylation rates among supported Rh-based catalysts. This study demonstrates the role of coordination-tuning via a secondary metal in effectively controlling the reaction pathway over single Rh atom catalysts.
03 NATURAL GAS↗
Materials Data on H3Ru3Rh(CO)12 by Materials Project
Rh(RuH(CO)3)3(CO)3 crystallizes in the triclinic P-1 space group. The structure is zero-dimensional and consists of six formaldehyde molecules, two rhodium molecules, and two RuH(CO)3 clusters. In each RuH(CO)3 cluster, there are three inequivalent Ru+3.33+ sites. In the first Ru+3.33+ site, Ru+3.33+ is bonded in a 5-coordinate geometry to three C+0.67+ and two H1+ atoms. There is one shorter (1.90 Å) and two longer (1.91 Å) Ru–C bond length. There is one shorter (1.79 Å) and one longer (1.83 Å) Ru–H bond length. In the second Ru+3.33+ site, Ru+3.33+ is bonded in a 5-coordinate geometry to three C+0.67+ and two H1+ atoms. All Ru–C bond lengths are 1.91 Å. Both Ru–H bond lengths are 1.80 Å. In the third Ru+3.33+ site, Ru+3.33+ is bonded in a 5-coordinate geometry to three C+0.67+ and two H1+ atoms. All Ru–C bond lengths are 1.91 Å. There is one shorter (1.79 Å) and one longer (1.80 Å) Ru–H bond length. There are nine inequivalent C+0.67+ sites. In the first C+0.67+ site, C+0.67+ is bonded in a single-bond geometry to one Ru+3.33+ and one O2- atom. The C–O bond length is 1.16 Å. In the second C+0.67+ site, C+0.67+ is bonded in a single-bond geometry to one Ru+3.33+ and one O2- atom. The C–O bond length is 1.16 Å. In the third C+0.67+ site, C+0.67+ is bonded in a single-bond geometry to one Ru+3.33+ and one O2- atom. The C–O bond length is 1.16 Å. In the fourth C+0.67+ site, C+0.67+ is bonded in a single-bond geometry to one Ru+3.33+ and one O2- atom. The C–O bond length is 1.16 Å. In the fifth C+0.67+ site, C+0.67+ is bonded in a single-bond geometry to one Ru+3.33+ and one O2- atom. The C–O bond length is 1.16 Å. In the sixth C+0.67+ site, C+0.67+ is bonded in a single-bond geometry to one Ru+3.33+ and one O2- atom. The C–O bond length is 1.16 Å. In the seventh C+0.67+ site, C+0.67+ is bonded in a single-bond geometry to one Ru+3.33+ and one O2- atom. The C–O bond length is 1.16 Å. In the eighth C+0.67+ site, C+0.67+ is bonded in a single-bond geometry to one Ru+3.33+ and one O2- atom. The C–O bond length is 1.16 Å. In the ninth C+0.67+ site, C+0.67+ is bonded in a single-bond geometry to one Ru+3.33+ and one O2- atom. The C–O bond length is 1.16 Å. There are three inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a water-like geometry to two Ru+3.33+ atoms. In the second H1+ site, H1+ is bonded in a water-like geometry to two Ru+3.33+ atoms. In the third H1+ site, H1+ is bonded in a water-like geometry to two Ru+3.33+ atoms. There are nine inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to one C+0.67+ atom. In the second O2- site, O2- is bonded in a single-bond geometry to one C+0.67+ atom. In the third O2- site, O2- is bonded in a single-bond geometry to one C+0.67+ atom. In the fourth O2- site, O2- is bonded in a single-bond geometry to one C+0.67+ atom. In the fifth O2- site, O2- is bonded in a single-bond geometry to one C+0.67+ atom. In the sixth O2- site, O2- is bonded in a single-bond geometry to one C+0.67+ atom. In the seventh O2- site, O2- is bonded in a single-bond geometry to one C+0.67+ atom. In the eighth O2- site, O2- is bonded in a single-bond geometry to one C+0.67+ atom. In the ninth O2- site, O2- is bonded in a single-bond geometry to one C+0.67+ atom.
36 MATERIALS SCIENCE↗
Performance of a CO 2 sorbent for indoor air cleaning applications: Effects of environmental conditions, sorbent aging, and adsorption of co-occurring formaldehyde
Indoor air cleaning systems that incorporate CO 2 sorbent materials enable HVAC load shifting and efficiency improvements. This study developed a bench-scale experimental system to evaluate the performance of a sorbent under controlled operation conditions. A thermostatic holder containing 3.15 g sorbent was connected to a manifold that delivered CO 2 -enriched air at a known temperature and relative humidity (RH). The air stream was also enriched with 0.8-2.1 ppm formaldehyde. The CO 2 concentration was monitored in real-time upstream and downstream of the sorbent, and integrated formaldehyde samples were collected at different times using DNPH-coated silica cartridges. Sorbent regeneration was carried out by circulating clean air in countercurrent. Almost 200 loading/regeneration cycles were performed in the span of 17 months, from which 104 were carried out at reference test conditions defined by loading with air at 25°C, 38% RH, and 1000 ppm CO 2 , and regenerating with air at 80°C, 3% RH and 400 ppm CO 2 . The working capacity decreased slightly from 43-44 mg CO 2 per g sorbent to 39-40 mg per g over the 17 months. The capacity increased with lower loading temperature (in the range 15-35°C) and higher regeneration temperature, between 40 and 80°C. The CO 2 capacity was not sensitive to the moisture content in the range 6-9 g/m 3 , and decreased slightly when dry air was used. Loading isothermal breakthrough curves were fitted to three simple adsorption models, verifying that pseudo-first-order kinetics appropriately describes the adsorption process. The model predicted that equilibrium capacities decreased with increasing temperature from 15 to 35°C, while adsorption rate constants slightly increased. The formaldehyde adsorption efficiency was 80%-99% in different cycles, corresponding to an average capacity of 86 ± 36 µg/g. Formaldehyde was not quantitatively released during regeneration, but its accumulation on the sorbent did not affect CO 2 adsorption.
32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
Investigation of Rh–titanate (ATiO 3 ) interactions on high-surface-area perovskite thin films prepared by atomic layer deposition
Thin, ~1 nm films of CaTiO 3 , SrTiO 3 , and BaTiO 3 were deposited onto MgAl 2 O 4 by Atomic Layer Deposition (ALD) and studied as catalyst supports for Rh. Scanning Transmission Electron Microcopy (STEM) and X-Ray Diffraction (XRD) demonstrated that the films had the perovskite structure and formed uniform coatings stable up to 1073 K. Rh, added by ALD, interacted strongly with CaTiO 3 and somewhat less strongly with SrTiO 3 , while Rh on BaTiO 3 was similar to Rh on unmodified MgAl 2 O 4 . STEM measurements of Rh on CaTiO 3 films showed Rh remained well dispersed after repeated oxidations and reductions at 1073 K; however, the Rh was inactive for CO-oxidation. Rh formed small particles on SrTiO 3 films and was active for CO oxidation after reduction at 1073 K. The reducibility and catalytic activity of Rh/BaTiO 3 /MgAl 2 O 4 were similar to that of Rh/MgAl 2 O 4 . Evidence from CO-TPR, FTIR, and XPS all indicated that the degree of interaction between Rh and the three perovskite films can be ranked in the following order: Rh/CaTiO 3 /MgAl 2 O 4 > Rh/SrTiO 3 /MgAl 2 O 4 > Rh/BaTiO 3 /MgAl 2 O 4 . Here, bulk ex-solution catalysts, synthesized by reduction of ATi 0.98 Rh 0.02 O 3 (A = Ca, Sr, and Ba), were also examined for comparison.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Materials Data on Co(BRh2)3 by Materials Project
Co(Rh2B)3 crystallizes in the monoclinic Cm space group. The structure is three-dimensional. there are nine inequivalent Rh sites. In the first Rh site, Rh is bonded in a 3-coordinate geometry to three B atoms. There are one shorter (2.09 Å) and two longer (2.19 Å) Rh–B bond lengths. In the second Rh site, Rh is bonded in a 3-coordinate geometry to three B atoms. There are a spread of Rh–B bond distances ranging from 2.10–2.24 Å. In the third Rh site, Rh is bonded in a 3-coordinate geometry to three B atoms. There are one shorter (2.15 Å) and two longer (2.21 Å) Rh–B bond lengths. In the fourth Rh site, Rh is bonded in a 3-coordinate geometry to three B atoms. There are a spread of Rh–B bond distances ranging from 2.12–2.23 Å. In the fifth Rh site, Rh is bonded in a 3-coordinate geometry to three B atoms. There are one shorter (2.18 Å) and two longer (2.19 Å) Rh–B bond lengths. In the sixth Rh site, Rh is bonded in a 3-coordinate geometry to three B atoms. There are one shorter (2.15 Å) and two longer (2.16 Å) Rh–B bond lengths. In the seventh Rh site, Rh is bonded in a distorted water-like geometry to two equivalent B atoms. Both Rh–B bond lengths are 2.12 Å. In the eighth Rh site, Rh is bonded in a 2-coordinate geometry to two B atoms. There are one shorter (2.15 Å) and one longer (2.16 Å) Rh–B bond lengths. In the ninth Rh site, Rh is bonded in a distorted water-like geometry to two equivalent B atoms. Both Rh–B bond lengths are 2.12 Å. Co is bonded in a 2-coordinate geometry to two B atoms. There are one shorter (2.10 Å) and one longer (2.13 Å) Co–B bond lengths. There are four inequivalent B sites. In the first B site, B is bonded in a 6-coordinate geometry to four Rh and two equivalent Co atoms. In the second B site, B is bonded in a 6-coordinate geometry to five Rh and one Co atom. In the third B site, B is bonded in a 6-coordinate geometry to six Rh atoms. In the fourth B site, B is bonded in a 6-coordinate geometry to six Rh atoms.
36 MATERIALS SCIENCE↗
Environment of Metal–O–Fe Bonds Enabling High Activity in CO 2 Reduction on Single Metal Atoms and on Supported Nanoparticles
Single-atom catalysts are often reported to have catalytic properties that surpass those of nanoparticles, while a direct comparison of sites common and different for both is lacking. In this work, we show that single atoms of the Pt-group embedded into the surface of Fe 3 O 4 have a greatly enhanced interaction strength with CO 2 compared with Fe 3 O 4 surface. The strong CO 2 adsorption on single Rh atoms and corresponding low activation energies lead to two-orders-of-magnitude higher conversion rates of CO 2 compared to Rh nanoparticles. This high activity of single atoms stems from the partially oxidic state imposed by their coordination to the support. Fe 3 O 4 -supported Rh nanoparticles follow the behavior of single atoms for CO 2 interaction and reduction, which is attributed to the dominating role of partially oxidic sites at the Fe 3 O 4 -Rh interface. Thus, we show a likely common catalytic chemistry for two kinds of materials thought to be different, and we show that single atoms of Pt-group metals on Fe 3 O 4 are an especially successful material for catalyzed reactions that depend primarily upon sites with the metal-O-Fe environment.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Quantum critical behavior of the hyperkagome magnet Mn 3 CoSi
β -Mn-type family alloys Mn 3 T X ( T = Co , Rh, and Ir; X = Si and Ge) have a three-dimensional antiferromagnetic (AF) corner-shared triangular network, i.e., the hyperkagome lattice. The antiferromagnet Mn 3 RhSi shows magnetic short-range order over a wide temperature range of approximately 500 K above the Néel temperature T N of 190 K. In this family of compounds, as the lattice parameter decreases, the long-range magnetic ordering temperature decreases. Mn 3 CoSi has the smallest lattice parameter and the lowest T N in the family. The quantum critical point (QCP) from AF to the quantum paramagnetic state is expected near a cubic lattice parameter of 6.15 Å . Although the Néel temperature of Mn 3 CoSi is only 140 K, the emergence of the quantum critical behavior in Mn 3 CoSi is discussed. We study how the magnetic short-range order appears in Mn 3 CoSi by using neutron scattering, μ SR , and bulk characterization such as specific heat capacity. According to the results, the neutron scattering intensity of the magnetic short-range order in Mn 3 CoSi does not change much at low temperatures from that of Mn 3 RhSi , although the μ SR short-range order temperature of Mn 3 CoSi is largely suppressed to 240 K from that of Mn 3 RhSi . Correspondingly, the volume fraction of the magnetic short-range order regions, as shown by the initial asymmetry drop ratio of μ SR above T N , also becomes small. Instead, the electronic-specific heat coefficient γ of Mn 3 CoSi is the largest in this Mn 3 T Si system, possibly due to the low-energy spin fluctuation near the quantum critical point. Published by the American Physical Society 2024
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
Beyond Thermal Limits: Manipulating Reactive Intermediate Coverages and Turnover Rates via Visible Photon-Mediated Catalysis on Rh-Doped Perovskite Oxides
Catalyst behavior depends on surface adsorbate energetics that are constrained by scaling relationships on metal surfaces. External stimuli (e.g., photons), however, can disrupt these limitations by modulating key intermediate coverages via non-thermal reaction pathways. Here, low-energy visible photon fluxes are utilized to selectively control coverages of strongly bound intermediates on isolated Rh active sites doped within a semiconductor perovskite oxide host (SrTiO 3 ). Red light (632 nm) facilitates selective photolytic CO desorption from rhodium gem-dicarbonyl (Rh(CO) 2 ) species that are ubiquitous reaction intermediates, including for the probe reaction studied herein CO oxidation to CO 2 . Thermochemical CO 2 formation rates (408 K) on Rh-doped SrTiO 3 are limited by adsorbed CO, exhibiting a negative apparent CO rate order (−0.6) and a positive O 2 rate order (+0.4). Arrhenius analyses, anaerobic CO oxidation measurements, and in situ spectroscopies assert that, thermochemically, lattice oxygens from the doped perovskite contribute to CO 2 formation rates. Notably, under red light illumination (0.76–2.02 W cm –2 ), the apparent CO rate order shifts to positive (+1). This, combined with decreasing apparent activation energies and CO coverages (wavelength-agnostic) with increasing photon flux, indicates that photons act selectively toward driving Rh(CO) 2 photolysis, even within complex reaction networks, thereby enhancing Rh accessibility, O 2 dissociation, and consequent rates. Finally, low-energy red light enables more stoichiometric feeds, leading to 650% higher CO 2 rates than those achieved thermally. Overall, this work elucidates how low-energy light can be leveraged, not just to improve reaction rates, but to selectively affect rates of individual elementary steps and key intermediate coverages, thereby breaking conventional scaling relationships that limit thermal catalyst performance.
catalysts↗
Electrochemistry in the Large Tunnels of Lithium Postspinel Compounds
Lithium spinels (Li MM 'O 4 ) are an important class of mixed-cation materials that have found uses in batteries, catalysis, and optics. Postspinels are a series of related framework structures with the AMM 'O 4 host composition that are formed with larger A -site cations, typically under high pressure. Postspinels have one-dimensional tunnel structures with pores that are larger than those in spinel and triangular in cross-section, but they are relatively unexplored as intercalation electrodes. While lithium postspinels have been previously found to be thermodynamically stable only at high pressures, we have identified a synthetic pathway that produces the lithium-containing materials at ambient pressure using an ion-exchange process from the corresponding sodium postspinels. Here, in this work, we report the synthesis and a survey of the electrochemical properties of 10 new lithium CaFe 2 O 4 -type postspinel compounds where M = Mn 3+ , V 3+ , Cr 3+ , Rh 3+ , Fe 2+ , Mg 2+ , Co 2+ and M ' = Ti 4+ and/or Sn 4+ . Although complete delithiation is not achieved during electrochemical cycling, many of the lithium postspinels have substantial charge storage capacity in Li battery cells owing to the ability of the large framework tunnels to accommodate more than one lithium ion per formula unit. Multiple redox couples are accessed for LiMnSnO 4 , Li 0.96 Mn 0.96 Sn 1.04-x Ti x O 4 , Li 0.96 V 0.96 Ti 1.04 O 4 , Li 0.96 Cr 0.96 Ti 1.04 O 4 , and LiFe 0.5 Ti 1.5 O 4 . Compositions with moderate or poor lithium cyclability are also discussed for comparison. Redox mechanisms and trends are identified by comparing this new redox-active framework to related spinels, ramsdellites, and 'Na 0.44 MnO 2 ' structures, and from density functional theory (DFT) electronic structures. Operando diffraction shows complex structural responses to lithium insertion and extraction in this postspinel framework. A DFT framework was proposed to identify promising lithium postspinel phases that could be accessed metastably under ambient pressure conditions and to assess their stability to lithium insertion and extraction. This work suggests that CaFe 2 O 4 -type hosts are a promising new class of lithium-ion energy storage materials.
25 ENERGY STORAGE↗
Ultrasound-driven fabrication of high-entropy alloy nanocatalysts promoted by alcoholic ionic liquids
High-entropy alloy nanoparticles (HEA-NPs) are highly underutilized in heterogeneous catalysis due to the absence of a reliable, sustainable, and facile synthetic method. Herein, we report a facile synthesis of HEA nanocatalysts realized via an ultrasound-driven wet chemistry method promoted by alcoholic ionic liquids (AILs). Owing to the intrinsic reducing ability of the hydroxyl group, AILs were synthesized and utilized as environmentally friendly alternatives to conventional reducing agents and volatile organic solvents in the synthetic process. Under high-intensity ultrasound irradiation, Au 3+ , Pd 2+ , Pt 2+ , Rh 3+ , and Ru 3+ ions were co-reduced and transformed into single-phase HEA (AuPdPtRhRu) nanocrystals without calcination. Characterization results reveal that the as-synthesized nanocrystals are composed of elements of Au, Pd, Pt, Rh, and Ru as expected. Compared to the monometallic counterparts such as Pd-NPs, the carbon-supported HEA nanocatalysts show superior catalytic performance for selective hydrogenation of phenol to cyclohexanone in terms of yield and selectivity. Our synthetic strategy provides an improved and facile methodology for the sustainable synthesis of multicomponent alloys for catalysis and other applications.
36 MATERIALS SCIENCE↗
Preparation and Characterization of Model Homotopic Catalysts: Rh Adatoms, Nanoparticles, and Mixed Oxide Surfaces on Fe 3 O 4 (001)
The atomic-level characterization of active sites is essential to understanding the mechanisms behind catalytic reactions. In this study, using scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS), we follow the morphological changes of a model Rh catalysts supported on Fe 3 O 4 (001) as a function of temperature and Rh coverage. Here, we identify the preparation conditions leading to model catalysts containing homotopic or nearly homotopic Rh species bound as adatoms, small clusters, substitutional within the Fe 3 O 4 (001), and nanoparticles. Adsorbates such as CO and CO 2 are further subsequently used to characterize the properties of different Rh sites. Using temperature programmed desorption (TPD), we demonstrate that adatoms, clusters, and nanoparticles exhibit high-temperature CO desorption (250-600 K). Strong binding on such sites further allows for CO oxidation to CO 2 via the Mars-van-Krevelen mechanism. In contrast, CO 2 was found to interact weakly with all Rh sites. Differences in desorption temperature enable the use of CO and CO 2 as titration methods for nanoparticles and Fe 3 O 4 (001), respectively. A small quantity of CO 2 was found to be reduced to CO on Rh adatoms and clusters.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Effects of de-fluorination on hydrophobicity and on CO 2 and CH 4 adsorption under high humidity in MeMOFs, methylated analogues of FMOFs
Superhydrophobicity of MeMOFs, methylated analogues of FMOFs (CF 3 → CH 3 ) is predicted by GCMC simulations (high-RH CO 2 or CH 4 adsorption in MeMOFs > FMOFs) validated experimentally (H 2 O contact angle ∼172° for MeMOF@plastic dry-coated substrates).
Yasmeen, Rashida [Department of Materials Science ↗
Quantum oscillation studies of the nodal line semimetal Ni 3 In 2 S 2-x Se x
Ternary shandite compounds with the general formula T 3 M 2 X 2 (T = Ni, Co, Rh or Pd; M = Sn, In, or Pb; and X = S or Se) have emerged as a large pool of topological semimetals. This family of compounds hosts different topological phases for various combinations of T, M and X. This paper reports the observation of quantum oscillations under the high magnetic fields in Ni 3 In 2 S 2-x Se x single crystals. Angular dependence of oscillation frequency suggests an evolution of the Fermi surface from three-dimensional to two-dimensional on Se substitution for S in Ni 3 In 2 S 2 . Here, the effective mass obtained for each composition by fitting the oscillation amplitude with the Lifshitz-Kosevich formula, shows no significant change, suggesting that the topological phase might be relatively robust against enhanced spin-orbit coupling upon Se doping in Ni 3 In 2 S 2 .
36 MATERIALS SCIENCE↗
Influence of support on Rh-Co bimetallic catalysts for ethylene hydroformylation
Bimetallic Rh- and Co-based catalysts are promising materials for the heterogenous ethylene hydroformylation reaction. Here, in this study, the influence of a mesoporous silica (SBA-15) support on Rh and Co bimetallic interactions was investigated through a comparison with silica gel and alumina supports. The bimetallic catalyst supported on mesoporous silica (RhCo 3 /SBA-15) showed the best C 3 oxygenate yield among the three bimetallic catalysts. In-situ vibrational studies suggested moderate binding of the gem-dicarbonyl and Rh(CO)(C 2 H 4 ) intermediates due to this bimetallic interaction that led to improved hydroformylation performance. Kinetic studies revealed a lower hydroformylation barrier for the bimetallic compared to a Rh monometallic catalyst, and in-situ X-ray absorption spectroscopy investigations showed clear Rh-Co alloy formation on RhCo 3 /SBA-15. The bimetallic enhancement effect from the interaction with the mesoporous silica support shown here can be further optimized to design olefin hydroformylation catalysts.
58 GEOSCIENCES↗