Assembling Phenothiazine into a Porous Coordination Cage to Improve Its Photocatalytic Efficiency for Organic Transformations.

Photo-catalysis by small-molecules is often limited by catalyst degradation and low electron-transfer efficiency. Herein we report a stable N-phenyl-phenothiazine (PTH)-derived porous coordination cage (PCC) as a highly efficient photocatalyst. By the incorporation of the photocatalytic PTH moiety into a PCC, aggregation-induced quenching (AIQ) was shown to be reduced. An improvement in catalyst stability was discovered, ascribed to the synergistic effects of the PTH moieties. The catalyst, operating through a photolytic single-electron transfer, was utilized for photo-catalyzed dehalogenation and borylation. Evaluation of the catalytic mechanism in the borylation reaction showed that the improved performance results from the more efficient formation of the electron donor-acceptor (EDA) complex with the cage. This discovery provides a potential strategy to improve the photophysical properties and stabilities of small-molecule organic photocatalysts via supramolecular chemistry.

Electrical conductivity through π-π stacking in a two-dimensional porous gallium catecholate metal-organic framework.

Metal-organic frameworks (MOFs) are hybrid materials known for their nanoscale pores, which give them high surface areas but generally lead to poor electrical conductivity. Recently, MOFs with high electrical conductivity were established as promising materials for a variety of applications in energy storage and catalysis. Many recent reports investigating the fundamentals of charge transport in these materials focus on the role of the organic ligands. Less consideration, however, is given to the metal ion forming the MOF, which is almost exclusively a late first-row transition metal. Here, we report a moderately conductive porous MOF based on trivalent gallium and 2,3,6,7,10,11-hexahydroxytriphenylene. Gallium, a metal that has not been featured in electrically conductive MOFs so far, has a closed-shell electronic configuration and is present in its trivalent state-in contrast to most conductive MOFs, which are formed by open-shell, divalent transition metals. Our material, made without using any harmful solvents, displays conductivities on the level of 3 mS/cm and a surface area of 196 m2 /g, comparable to transition metal analogs.

Porous lanthanide metal-organic frameworks with metallic conductivity.

Metallic charge transport and porosity appear almost mutually exclusive. Whereas metals demand large numbers of free carriers and must have minimal impurities and lattice vibrations to avoid charge scattering, the voids in porous materials limit the carrier concentration, provide ample space for impurities, and create more charge-scattering vibrations due to the size and flexibility of the lattice. No microporous material has been conclusively shown to behave as a metal. Here, we demonstrate that single crystals of the porous metal-organic framework Ln1.5(2,3,6,7,10,11-hexaoxytriphenylene) (Ln = La, Nd) are metallic. The materials display the highest room-temperature conductivities of all porous materials, reaching values above 1,000 S/cm. Single crystals of the compounds additionally show clear temperature-deactivated charge transport, a hallmark of a metallic material. Lastly, a structural transition consistent with charge density wave ordering, present only in metals and rare in any materials, provides additional conclusive proof of the metallic nature of the materials. Our results provide an example of a metal with porosity intrinsic to its structure. We anticipate that the combination of porosity and chemical tunability that these materials possess will provide a unique handle toward controlling the unconventional states that lie within them, such as charge density waves that we observed, or perhaps superconductivity.

Challenges in current construction and demolition waste recycling: A China study.

China produced a large amount of construction and demolition (C&D) waste, owing to the rapid development of construction industry. Although a set of policies and regulations are being drafted in China for promoting C&D waste recycling, execution of these policies in practice seems to be far from effective. Currently, approximately 75% of Chinese cities are still surrounded by large volumes of C&D waste. Therefore, identification of challenges in the development of C&D waste management, specially recycling, is essential. This paper employs site visits to 10 recycling plants in 10 Chinese cities (Shanghai, Hangzhou, Suzhou, Chongqing, Chengdu, Xi'an, Changsha, Shenzhen, Nanjing, and Zhoukou) and interviews with 25 industry practitioners for examining the challenges. Eight challenges are identified: (1) unstable source of C&D waste for recycling, (2) absence of subsidies for recycling activities and high cost for land use, (3) insufficient attention paid to design for waste minimisation, (4) absence of regulations on on-site sorting, (5) unregulated landfill activities, (6) a lack of coordination among different government administration departments, (7) a lack of accurate estimation of waste quantity and distribution, and (8) a lack of an effective waste tracing system. Recommendations to address these challenges are presented. The results of this study are expected to aid policy makers in formulation of proper C&D waste management in China and provide a useful reference for researchers who are interested in C&D waste recycling industry.

Soft Mode Metal-Linker Dynamics in Carboxylate MOFs Evidenced by Variable-Temperature Infrared Spectroscopy.

Through comprehensive analysis of carboxylate-based metal-organic frameworks (MOFs), we present general evidence that challenges the common perception of MOF metal-linker bonds being static. Structural dynamics in MOFs, however, typically refers to the "breathing" behavior of cavities, where pores open and close in response to guest molecules, and to the transient binding of guest molecules, but dynamic bonding would explain important MOF phenomena in catalysis, postsynthetic exchange, negative thermal expansion, and crystal growth. Here, we demonstrate, through use of variable-temperature diffuse reflectance infrared Fourier transform spectroscopy (VT-DRIFTS) aided by ab initio plane wave density functional theory, that similar evidence for melting behavior in zeolitic imidazolate frameworks (ZIFs), i.e., reversible metal-linker bonding, driven by specific vibrational modes, can be observed for carboxylate MOFs by monitoring the red-shifts of carboxylate stretches coupled to anharmonic metal-carboxylate oscillators. To demonstrate the generality of these findings, we investigate a wide class of carboxylate MOFs that includes iconic examples with diverse structures and metal-linker chemistry. As the very vibrations invoked in ZIF melting but heretofore unobserved for carboxylate MOFs, these metal-linker dynamics resemble the ubiquitous soft modes that trigger important phase transitions in diverse classes of materials while offering a fundamentally new perspective for the design of next-generation metal-organic materials.

Electronic Structure Modeling of Metal-Organic Frameworks.

Owing to their molecular building blocks, yet highly crystalline nature, metal-organic frameworks (MOFs) sit at the interface between molecule and material. Their diverse structures and compositions enable them to be useful materials as catalysts in heterogeneous reactions, electrical conductors in energy storage and transfer applications, chromophores in photoenabled chemical transformations, and beyond. In all cases, density functional theory (DFT) and higher-level methods for electronic structure determination provide valuable quantitative information about the electronic properties that underpin the functions of these frameworks. However, there are only two general modeling approaches in conventional electronic structure software packages: those that treat materials as extended, periodic solids, and those that treat materials as discrete molecules. Each approach has features and benefits; both have been widely employed to understand the emergent chemistry that arises from the formation of the metal-organic interface. This Review canvases these approaches to date, with emphasis placed on the application of electronic structure theory to explore reactivity and electron transfer using periodic, molecular, and embedded models. This includes (i) computational chemistry considerations such as how functional, k-grid, and other model variables are selected to enable insights into MOF properties, (ii) extended solid models that treat MOFs as materials rather than molecules, (iii) the mechanics of cluster extraction and subsequent chemistry enabled by these molecular models, (iv) catalytic studies using both solids and clusters thereof, and (v) embedded, mixed-method approaches, which simulate a fraction of the material using one level of theory and the remainder of the material using another dissimilar theoretical implementation.

Pressure-induced metallicity and piezoreductive transition of metal-centres in conductive 2-dimensional metal-organic frameworks.

Due to their generally poor conductivity, metal-organic frameworks (MOFs) have been limited in electrical applications. The highest performing materials are two-dimensionally connected Ni3(hexaiminotriphenylene)2 and Ni3(hexaiminobenzene)2; both feature experimental conductivities exceeding 500 S m-1. From theory, both are predicted to be bulk metals but the former is known to be a semiconductor within a single monolayer. In this work we explore structural deformation as a route to augmenting the electronic properties of these two high performing materials. We show that, under hydrostatic negative pressure, metallicity can be installed in the Ni3(hexaiminotriphenylene)2 monolayer. Further, we predict a unique piezoreduction of metal ions and induced-magnetization in Ni3(hexaiminobenzene)2 due to the shift in energy of metal-ligand bonding and antibonding orbitals. These observations aid in our understanding of how MOFs conduct electricity and may also be used as a design principle in future MOF technologies.

Quantifying the effects of general waste reduction on greenhouse-gas emissions at public facilities.

Global municipal solid waste (MSW) amounts to approximately 1.3 billion tons per year and is expected to increase to approximately 2.2 billion tons per year by 2025. The greenhouse gas (GHG) emissions from landfills contribute to global climate change. Emissions from this sector contribute around 3% of total net emissions in Australia. Although responsible for a minor portion of Australia's emissions, the sector provides the opportunity for low-cost sources of abatement. This research study aimed to identify new opportunities for reducing GHG emissions from the landfill waste stream in public facilities in Blacktown City in New South Wales, Australia. For this purpose, two public facilities of different types were selected, a library and an aquatic center. The results of the study show that removing organic food waste from the landfill stream at 10 public facilities of the Council could reduce GHG emissions compared with landfilling the food waste by about 0.805 tCO2e/year. However, separately transporting that waste would emit 7.13 tCO2e/year. Therefore, the separated food waste would need to be processed on-site, for example, through worm farms. Removing coffee cups from the landfill waste stream could reduce the associated landfill GHG emissions by around 0.275 tCO2e/y for the 10 public facilities. The study also recommended separating plastic bags from the landfill waste stream of these facilities to reduce 1.10 tonnes of plastic bags from landfill each year. Implications: Potential opportunities for general waste reduction and GHG emission mitigation in public facilities has been studied in this paper. Removing coffee cups and organics food from the waste stream are the main potential opportunities for reducing general waste with possible GHG emission reduction of 0.275 tCO2e/y and 0.161 tCO2/y respectively for 10 public facilities. Removing plastic bags from the waste stream would offer another solution for waste reduction by jointing with the large program running in Australia and creating a collection point for them with 1.1 tonne/y mitigation in general waste at 10 studied public facilities.

Sorodiplophrys stercorea: Another Novel Lineage of Sorocarpic Multicellularity.

Sorodiplophrys stercorea is a sorocarpic organism that utilizes filose pseudopodia for locomotion and absorptive nutrition. It has traditionally been considered to be a member of the Labyrinthulae based on its morphology. Its closest relatives were thought to be species in the taxon Diplophrys. Since the genus Diplophrys has been shown to be paraphyletic and S. stercorea has pseudopodia similar to some members of Rhizaria, we examined its relationship with other eukaryotes. We obtained four isolates from the dung of cow and horse, brought each into monoeukaryotic culture, and sequenced their SSU rRNA gene for phylogenetic analysis. All our isolates were shown to form a monophyletic group in the Labyrinthulae, nested in the Amphifiloidea clade. Our results demonstrate that Sorodiplophrys is more closely related to species of the genus Amphifila than to Diplophrys and represents an additional independent origin of sorocarpic multicellularity among eukaryotes. This study represents the first confirmed sorocarpic lifestyle in the Stramenopiles.

Cross-cultural comparison of concrete recycling decision-making and implementation in construction industry.

Waste management is pressing very hard with alarming signals in construction industry. Concrete waste constituents major proportions of construction and demolition waste of 81% in Australia. To minimize concrete waste generated from construction activities, recycling concrete waste is one of the best methods to conserve the environment. This paper investigates concrete recycling implementation in construction. Japan is a leading country in recycling concrete waste, which has been implementing 98% recycling and using it for structural concrete applications. Hong Kong is developing concrete recycling programs for high-grade applications. Australia is making relatively slow progress in implementing concrete recycling in construction. Therefore, empirical studies in Australia, Hong Kong, and Japan were selected in this paper. A questionnaire survey and structured interviews were conducted. Power spectrum was used for analysis. It was found that "increasing overall business competitiveness and strategic business opportunities" was considered as the major benefit for concrete recycling from Hong Kong and Japanese respondents, while "rising concrete recycling awareness such as selecting suitable resources, techniques and training and compliance with regulations" was considered as the major benefit from Australian respondents. However, "lack of clients' support", "increase in management cost" and "increase in documentation workload, such as working documents, procedures and tools" were the major difficulties encountered from Australian, Hong Kong, and Japanese respondents, respectively. To improve the existing implementation, "inclusion of concrete recycling evaluation in tender appraisal" and "defining clear legal evaluation of concrete recycling" were major recommendations for Australian and Hong Kong, and Japanese respondents, respectively.

Noise reduction in rhythmic and multitrial biosignals with applications to event-related potentials.

A new noise reduction algorithm is presented for signals displaying repeated patterns or multiple trials. Each pattern is stored in a matrix, forming a set of events, which is termed multievent signal. Each event is considered as an affine transform of a basic template signal that allows for time scaling and shifting. Wavelet transforms, decimated and undecimated, are applied to each event. Noise reduction on the set of coefficients of the transformed events is applied using either wavelet denoising or principal component analysis (PCA) noise reduction methodologies. The method does not require any manual selection of coefficients. Nonstationary multievent synthetic signals are employed to demonstrate the performance of the method using normalized mean square error against classical wavelet and PCA based algorithms. The new method shows a significant improvement in low SNRs (typically 0 dB). On the experimental side, evoked potentials in a visual oddball paradigm are used. The reduced-noise visual oddball event-related potentials reveal gradual changes in morphology from trial to trial (especially for N1-P2 and N2-P3 waves at Fz), which can be hypothetically linked to attention or decision processes. The new noise reduction method is, thus, shown to be particularly suited for recovering single-event features in nonstationary low SNR multievent contexts.

Optimal aggregate testing using Vandermonde polynomials and spectral methods.

Recycled aggregate (RA) has been used in various construction applications around the world mainly as sub-grade, roadwork and unbound materials, but not in higher-grade applications. The major barrier encountered is the variation of quality within RA, which causes lower strength, and poorer quality. This work studies the relationships among six parameters describing the characteristics of RA: (i) particle size distribution, (ii) particle density, (iii) porosity and absorption, (iv) particle shape, (v) strength and toughness, and (vi) chemical composition. Samples of RA from 10 demolition sites were obtained with service life ranging from 10 to 40 years. One additional set of samples was specifically collected from the Tuen Mun Area 38 Recycling Plant. The characteristics of these eleven sets of samples were then compared with normal aggregate samples. A Vandermonde matrix for interpolation polynomial coefficient estimation is used to give detailed mathematical relationships among pairs of samples, which can be used to work out redundant tests. Different orders of interpolation polynomials are used for comparison, hence the best-fit equations with the lowest fitting errors from different orders of polynomials can be found. Fitting error distributions are then studied by using spectral methods such as power spectra and bispectra. From that, the best equations for result estimations can be obtained. This study reveals that there is strong correlation among test parameters, and by measuring two of them: either "particle density" or "porosity and absorption" or "particle shape" or "strength and toughness", and "chemical content", it is sufficient to study RA.