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A cyanido-bridged Co–W assembly showing a charge transfer–induced phase transition realized room temperature bistability and red-blue drastic color change.

Indoor air humidity plays a vital role in determining occupants’ health and industrial product quality. Removing excess humidity by adsorption dehumidification is still facing a challenge in finding a suitable material with high adsorption capacity and low regeneration temperature. In this study, the theoretical dehumidification capacity of prepared acorn nutshell-based activated carbons was calculated and compared with silica gel type RD and RD-2060. The calculation was based on the outdoor air condition in two Asian capital cities: Jakarta and Tokyo. The theoretical study found that prepared activated carbon has better dehumidification performance under Jakarta conditions using regeneration temperatures of less than 60°C. Under Tokyo conditions, activated carbon shows auspicious performance during the summer season. Compared with silica gels, acorn nutshell-based activated carbon has a better dehumidification capacity to process high humidity ambient air with a lower regeneration temperature.

The demand for dehumidification in tropical regions contributes to a significant portion of the building energy consumption. Desiccant dehumidification can mitigate energy consumption by recovering the exergy potential from the waste heat and renewable energy sources. Material development is the bottleneck in realizing the full potential of desiccant dehumidification systems beyond conventional adsorbents such as silica gel and zeolite. Therefore, it is necessary to develop novel materials that can be regenerated using the heat source under 70°C. In this study, we developed activated carbons (ACs) as the desiccant materials derived from waste biomass. The ability of activated carbon (AC) to remove the moisture was controlled by carefully preparing the material using several conditions to achieve the right operation window for optimum moisture sorption processes. The porous and surface characteristics of the newly-prepared AC were analyzed and compared with those of silica gel. The adsorption isotherm measurements were conducted, and the data were fitted with Henry-Sips and Do-Do isotherm models. The current AC exhibited an excellent water adsorption capacity (up to 0.41 g/g). The efficacy of the ACs for dehumidification applications was assessed using the weather data from several regions of Indonesia, from North Sumatera to Papua. The results revealed that under the studied conditions, the new desiccant material showed a better dehumidification capacity than silica gel. Moreover, the reported AC can be regenerated using temperatures as low as 40°C, which is readily available from waste heat, including the heat rejection from the condenser of any air-conditioning unit.

Self-assembly FeII complexes of phenazine (Phen), quinoxaline (Qxn), and 4,4'-trimethylenedipyridine (Tmp) with tetrahedral building blocks of [HgII(XCN)4]2- (X = S or Se) formed six new high-dimensional frameworks with the general formula of [Fe(L) m ][Hg(XCN)4]·solvents (L = Phen, m/X = 2/S, 1; L = Qxn, m/X = 2/S, 2; L = Qxn, m/X = 1/S, 3; L = Qxn, m/X = 1/Se, 3-Se; L = Tmp, m/X = 1/S, 4; and L = Tmp, m/X = 1/Se, 4-Se). 1, 3, and 3-Se show an intense sub-terahertz (sub-THz) absorbance of around 0.60 THz due to vibrations of the solvent molecules coordinated to the FeII ions and crystallization organic molecules. In addition, crystals of 1, 4, and 4-Se display low-frequency Raman scattering with exceptionally low values of 0.44, 0.51, and 0.53 THz, respectively. These results indicate that heavy metal FeII-HgII systems are promising platforms to construct sub-THz absorbers.

Uncommon lanthanides are used to construct luminescent molecular nanomagnets and a pioneering SMM-based optical thermometer utilizing Sm(iii) centres.

Activated carbon (AC) is produced by a physical or chemical activation process. Physical activation methods are commonly adopted in industry because of their low production costs, but the insufficiency of activating agent diffusibility into core parts of the particles and microdomains of carbon materials causes a lower activation yield and degree of pore development, compared with chemical activation methods. To increase the activating agent diffusibility and corresponding degree of pore development, we propose a novel pressurized physical activation method. Pressurization afforded remarkable increases in specific surface area and total pore volume of the prepared AC, compared with atmospheric pressure. Additionally, in AC prepared by this method, pore size distribution analysis revealed characteristic development of micropores of about 1.6 nm; such micropores did not appear in AC under conventional atmospheric physical activation. Furthermore, observations of particles and their microdomains showed that pressurization increased the activating agent diffusibility in carbon particles, but not at the microdomain level. This innovative pressurized physical activation can produce AC with highly developed pores (specific surface area >2600 m2/g) and a unique pore size distribution due to the improved activating agent diffusibility in carbon particles.

The effect of pore size on the response characteristic of an electric double layer capacitor (EDLC) was closely examined. A series of phenol-resin-based activated carbon (AC) samples was prepared as average pore size from 0.94 to 1.68 nm by KOH activation by varying the activation temperature and KOH/carbonized phenol-resin ratio. The impedance properties of pouch-type EDLC cells prepared using AC samples were evaluated by applying an alternating current at 3 V between 10 mHz and 100 kHz for confirming the response characteristic. The cell based on the AC with a largest pore size (1.68 nm) showed fast response frequency, and had a high dielectric relaxation time constant as calculated from the response frequency value. The AC with the largest pore size, which consisted of both micropores (>1 nm) and mesopores (2–4 nm), was confirmed to facilitate extremely low electrolyte-diffusion resistance during the formation of the electric double layer, implying that the large pores lead to fast and stable response frequency. The presented findings suggest that AC with a largest pore size as the electrode leads to superior capacitance and response frequency characteristics in the alternating current than those of an AC with a smaller pore size.

The green preparation of microporous activated carbon using acorn nutshell with different production conditions was studied. The heating rate and nitrogen flow rate were controlled during preparation. The effect of those conditions on the surface properties and water adsorption performance was observed. According to the results, the total surface area of acorn nutshells-based activated carbon can reach up to 993 m2/g with 90% microporosity and a total pore volume of 0.49 cm3/g. The water adsorption uptake under P/P0 = 0.9 of prepared material is up to 0.39 g/g. This study found that acorn nutshell shows potential performance as a precursor for producing highly microporous activated carbon, which might be suitable for water vapor adsorption.

Molecular vibrations in the solid-state, detectable in the terahertz (THz) region, are the subject of research to further develop THz technologies. To observe such vibrations in terahertz time-domain spectroscopy (THz-TDS) and low-frequency (LF) Raman spectroscopy, two supramolecular assemblies with the formula [NdIII (phen)3 (NCX)3] 0.3EtOH (X = S, 1-S; Se, 1-Se) were designed and prepared. Both compounds show several THz-TDS and LF-Raman peaks in the sub-THz range, with the lowest frequencies of 0.65 and 0.59 THz for 1-S and 1-Se, and 0.75 and 0.61 THz for 1-S and 1-Se, respectively. The peak redshift was observed due to the substitution of SCN− by SeCN−. Additionally, temperature-dependent TDS-THz studies showed a thermal blueshift phenomenon, as the peak position shifted to 0.68 THz for 1-S and 0.62 THz for 1-Se at 10 K. Based on ab initio calculations, sub-THz vibrations were ascribed to the swaying of the three thiocyanate/selenocyanate. Moreover, both samples exhibited near-infrared (NIR) emission from Nd (III), and very good thermometric properties in the 300–150 K range, comparable to neodymium (III) oxide-based thermometers and higher than previously reported complexes. Moreover, the temperature dependence of fluorescence and THz spectroscopy analysis showed that the reduction in anharmonic thermal vibrations leads to a significant increase in the intensity and a reduction in the width of the emission and LF absorption peaks. These studies provide the basis for developing new routes to adjust the LF vibrational absorption.

Coordination complexes of lanthanide(3+) ions can combine Single-Molecule Magnetism (SMM) with thermally modulated luminescence applicable in optical thermometry. We report an innovative approach towards high performance SMM-based optical thermometers which explores tunable anisotropy and the luminescence re-absorption effect of HoIII complexes. Our concept is shown in dinuclear cyanido-bridged molecules, {[HoIII(4-pyridone)4(H2O)2][MIII(CN)6]}·nH2O (M = Co, 1; Rh, 2; Ir, 3) and their magnetically diluted analogues, {[HoIIIxYIII1–x(4-pyridone)4(H2O)2][MIII(CN)6]}·nH2O (M = Co, x = 0.11, 1@Y; Rh, x = 0.12, 2@Y; Ir, x = 0.10, 3@Y). They are built of pentagonal bipyramidal HoIII complexes revealing the zero-dc-field SMM effect. Experimental studies and the ab initio calculations indicate an Orbach magnetic relaxation with energy barriers varying from 89.8 to 86.7 and 78.7 cm−1 K for 1, 2, and 3, respectively. 1–3 also differ in the strength of quantum tunnelling of magnetization which is suppressed by hyperfine interactions, and, further, by the magnetic dilution. The YIII-based dilution governs the optical properties as 1–3 exhibit poor emission due to the dominant re-absorption from HoIII while 1@Y–3@Y show room-temperature blue emission of 4-pyridone. Within ligand emission bands, the sharp re-absorption lines of the HoIII electronic transitions were observed. Their strong thermal variation was used in achieving highly sensitive ratiometric optical thermometers whose good performance ranges, lying between 25 and 205 K, are adjustable by using hexacyanidometallates. This work shows that HoIII complexes are great prerequisites for advanced opto-magnetic systems linking slow magnetic relaxation with unique optical thermometry exploiting a luminescence re-absorption phenomenon., HoIII complexes bearing organic luminophores and inorganic metalloligands are an effective tool for achieving the unique conjunction of single-molecule magnetism and thermometric luminescence re-absorption phenomenon.

Incorporating chiral organic ligands into cyanido-bridged FeII–NbIV assemblies synthesized chiral spin-crossover complexes, FeII2[NbIV(CN)8](L)8·6H2O (L = R-, S-, or rac-1-(3-pyridyl)ethanol: R-FeNb, S-FeNb, or rac-FeNb). Rietveld analyses based on a racemic complex of rac-FeNb indicate that the chiral complexes have a cubic crystal structure in the I213 space group with a three-dimensional cyanido-bridged FeII–NbIV coordination network. All the complexes exhibit spin crossover between the high-spin (HS) and the low-spin (LS) FeII states without thermal hysteresis. Chiral complexes of R-FeNb and S-FeNb show second harmonic generation (SHG) due to their non-centrosymmetric structure. The I213 space group provides second-order susceptibility tensor elements of χxyz, χyzx, and χzxy, which contribute to SHG. The temperature-dependent second harmonic light intensity change is due to spin crossover between FeIIHS and FeIILS.

We show an anomalous change in the phonon frequency at the magnetic phase transition on a cyanide-bridged bimetal assembly, Mn3[W(CN)8]2(pyrimidine)4·6H2O. This compound shows a frequency shift in the CN stretching mode below the magnetic phase transition temperature (TC). First-principles phonon mode calculation and molecular orbital calculation suggest that the frequency shift of the CN stretching mode is due to the competition of the magnetic energy and the elastic energy. This work demonstrates that a specific change in the phonon frequency is induced by long-range magnetic ordering in flexibly structured matter.

Adsorption thermal energy storage plays a vital role in supporting the availability of renewable energy. Activated carbons produced from local waste biomass have been attracting considerable attention in adsorption technology due to their unique properties and sustainability. However, their limitation in water vapor uptake hinders the practical application of this material. In this work, acorn nutshells were utilized as a base material to produce activated carbon. Air oxidation was performed as a versatile and low-cost technique to enhance the material’s properties and water adsorption capacity. By applying air oxidation as a post-treatment during material production, the amount of active functional groups and the water adsorption on activated carbon has been successfully enhanced. From the theoretical calculation, it is found that activated carbon–water working pairs shown promising performance to be used for adsorption thermal energy storage applications. The adsorption of water vapor on the post-treated-activated carbon releases the isosteric heat between 2400 kJ/kg to 2500 kJ/kg. Moreover, this study’s working pair can be driven by a temperature of less than 50 °C. From the results, it is confirmed that by controlling the adsorbent’s surface properties, activated carbon–water working pairs can be a promising way to provide alternative material and reduce the energy demand for driving the system.

This study demonstrates the differences in the capacitive behaviors between the pore structures generated by physical and chemical activation and infiltrated electrolyte ions in the pores. Three pa...

A research on the preparation of Carbon Waste Powder, CWP, was conducted and made from carbon rod waste which was extracted from used zinc-carbon batteries. This research was an effort to overcome environmental problem caused by battery waste by converting into adsorbent for methyl orange (MO) that frequently used by textile industries. The prepared powder was then analyzed to understand its characteristic peaks, crystallinity, and to compare the properties with other carbonaceous forms, i.e. a commercial Carbon Paper (CP), and a commercial meso- carbon micro-beads (MCMB). The analysis found that CWP is dominated by graphitic carbon. An adsorption experiment was then conducted to study their adsorption ability to methyl orange solution. The result found that those three carbonaceous materials have the ability to adsorb methyl orange with different activities. MCMB has the highest adsorption capacity of 0.197 mg.g-1. Meanwhile, CWP and CP show adsorption capacity of 0.066 mg.g-1 and 0.062 mg.g-1, respectively. Methyl orange adsorption on CWP and CP were under second order, which means the adsorption could be four times faster as the MO solution doubled. Moreover, the rate constant of MO adsorption on CWP is 8×10-4 min-1, which was higher than the rate constant of MO adsorption on CP. It confirmed that the CWP can be used as a promising adsorbent for dye waste water. Copyright © 2020 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Spinnable mesophase pitch with high pitch yield of more than 50 wt% was successfully prepared using direct bitumen coal extracted fraction through the three-step process of hydrogenation, N2 blowing heat treatment, and thin-layer evaporation. The prepared mesophase pitch was smoothly spun to the fibrous form and could be converted into mesophase pitch-based carbonized and graphitized fibers through the usual oxidative stabilization, carbonization, and graphitization. The prepared mesophase pitch based carbon fibers showed typical random transversal structures with mechanical performances, tensile strengths of 1.83 GPa and 3.00 GPa, Young’s moduli of 133 GPa and 450 GPa, and elongation properties of 1.37% and 0.68% after heat treatments at 1000 °C for 30 min and 2800 °C for 10 min, respectively. The relatively high-molecular-weight and well-developed polynuclear aromatic molecular structure of hypercoal is the likely reason for the high mesophase pitch yield. The meaning of each preparation processes, hydrogenation, N2 blowing heat treatment and thin layered evaporation, was discussed in detail. We anticipate that the success of high-yield mesophase pitch manufacturing using hypercoal as raw material will be an important key to innovatively reduce the production cost of mesophase pitch-based carbon fiber.

The 18th century industrial revolution dramatically changed people’s lives and allowed for rapid growth of the global economy. However, since that time, the mass consumption of fossil fuels has res...

Activated carbon is a suitable adsorbent for adsorption heat pumps (AHPs) with ethanol refrigerants. Although chemically activated carbon with highly developed pore structures exhibits good ethanol adsorption, the associated high production costs inhibit its practical application as an AHP adsorbent. Moreover, although physical activation can produce inexpensive activated carbon, the limited pore development limits the ethanol uptake. Recently, we developed a pressurized physical activation method that can produce activated carbon with a well-developed pore structure and characteristic pore size distribution. In this study, we investigated the applicability of the pressurized physically activated carbon as an adsorbent in activated carbon-ethanol AHP systems. Because of the large number of pressurization-induced pores of appropriate size, the pressurized physically activated carbon showed effective ethanol uptake comparable with that of chemically activated carbon on a weight basis. Furthermore, on a volume basis, the pressurized physically activated carbon, with a high bulk density, showed much higher effective ethanol uptake than chemically activated carbon. These results confirm the potential of the pressurized physically activated carbon as a relatively inexpensive high-performance adsorbent for AHP systems with ethanol refrigerants.

Urea/nitric acid co-impregnated pitch-based activated carbon fibers (ACFs) were examined as adsorbents for the removal of low-concentration formaldehyde gas from dry and humid atmospheres. Urea, which is a harmless and environmentally friendly primary amine, was selected as an effective reagent to capture formaldehyde and nitric acid was used to promote the oxidation of formaldehyde into formic acid, which inhibits the liberation of formaldehyde even under humid atmospheres. The optimized urea/nitric acid co-impregnated ACF showed a 110-fold (0.72 mg/g to 79.28 mg/g) improvement in its formaldehyde removal capability as compared to that of pristine ACF at 40% humidity. The formaldehyde removal mechanism is proposed based on careful analysis and quantification of the inlet and outlet gases. Further, the optimized sample facilitates complete removal of formaldehyde from ambient air at humidity of 11–88% and temperatures of 3–26.9 °C over 24 h, whereas only 81.5% formaldehyde removal is achieved with pristine ACF under the same conditions.

Better understanding of the changes in composition and molecular structures of atmospheric residue (AR) during hydrotreating is important for improving the hydrotreating performance of AR. Hydrotre...

It is important to understand the interaction of vanadyl complexes in atmospheric residue (AR) with their matrixes at different conditions for demetallization processes of AR and heavy oil. An ESR study in rotational mobility of vanadyl complexes in AR was conducted at a temperature range from 20 to 170 °C with and without 1-methylnaphthalene as solvent. A complete transformation of the ESR spectrum from anisotropy to isotropy was observed at a temperature of 170 °C with decreasing AR concentration in 1-methylnaphthalene from 100 to 20 wt %, which corresponds to a transformation of the vanadyl complexes from a rigid status constrained by the surrounding matrixes to a free status. Both increase in the temperature and decrease in the AR concentration are beneficial to such transformation. The study showed that dependency of the rotational mobility of vanadyl complexes on the temperature and concentration can be classified into three domains: isotropic, transitional, and anisotropic domains. In the anisotrop...

We report a unique synthetic route toward the multistep spin crossover (SCO) effect induced by utilizing the partial ligand transformation during the crystallization process, which leads to the inc...

Self-assembly of lanthanide(III) complexes of 2,2':6',2″-terpyridine (terpy) with dicyanidoargentate(I) and dicyanidoaurate(I) anions in water results in the formation of six isostructural dinuclear systems [Ln

We report a three-dimensional molecule-based magnet, [MnII3(4-pyridone)6][WV(CN)8]2·2H2O. This compound was synthesized in one-pot by evaporation of an aqueous solution in which MnCl2·4H2O, 4-hydroxypyridine and Cs3[W(CN)8]·2H2O were dissolved. The evaporation process causes self-assembly of the building blocks, forming a three-dimensional network structure with unique trimanganese units of [Mn3(4-pyridone)6]6+ bridged by [W(CN)8]3− anions. This compound has two types of short intermetallic bridges, which can exhibit two magnetic interaction pathways (MnII-O-MnII and MnII-NC-WV). The magnetic interactions between WV (S = 1/2) and MnII (S = 5/2) and between MnII and MnII are antiferromagnetic with exchange coupling constants of JMnW = −3.9 cm−1 and JMnMn = −5.9 cm−1, respectively. The present compound exhibits ferrimagnetism with spontaneous magnetization below 20 K.

Atomic vibrations due to stretching or bending modes cause optical phonon modes in the solid phase. These optical phonon modes typically lie in the frequency range of 102 to 104 cm−1. How much can the frequency of optical phonon modes be lowered? Herein we show an extremely low-frequency optical phonon mode of 19 cm−1 (0.58 THz) in a Rb-intercalated two-dimensional cyanide-bridged Co–W bimetal assembly. This ultralow frequency is attributed to a millefeuille-like structure where Rb ions are very softly sandwiched between the two-dimensional metal–organic framework, and the Rb ions slowly vibrate between the layers. Furthermore, we demonstrate temperature-induced and photo-induced switching of this low-frequency phonon mode. Such an external-stimulation-controllable sub-terahertz (sub-THz) phonon crystal, which has not been reported before, should be useful in devices and absorbers for high-speed wireless communications such as beyond 5G or THz communication systems., Extremely low-frequency optical phonon mode in Rb-intercalated two-dimensional cyanide-bridged Co–W bimetal assembly and its temperature- and photo-induced switching effect.