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The preparation of subnanoporous covalent-organic-framework (COF) membranes with high performance for ion/molecule sieving still remains a great challenge. In addition to the difficulties in fabricating large-area COF membranes, the main reason is that the pore size of 2D COFs is much larger than that of most gas molecules and/or ions. It is urgently required to further narrow their pore sizes to meet different separation demands. Herein, we report a simple and scalable way to grow large-area, pliable, free-standing COF membranes via a one-step route at organic–organic interface. The pore sizes of the membranes can be adjusted from >1 nm to sub-nm scale by changing the stacking mode of COF layers from AA to AB stacking. The obtained AB stacking COF membrane composed of highly-ordered nanoflakes is demonstrated to have narrow aperture (∼0.6 nm), uniform pore distribution and shows good potential in organic solvent nanofiltration, water treatment and gas separation. Fabrication of large scale and defect free covalent organic framework (COF) membranes with pores small enough for gas sieving remains challenging. Here, the authors report a scalable fabrication method to grow large area defect free COF membranes and to tune the pore size in the sub-nm region by adjusting the stacking modes of the COF layers.

Covalent organic frameworks show great potential in gas adsorption/separation, biomedicine, device, sensing, and printing arenas. However, covalent organic frameworks are generally not dispersible in common solvents resulting in the poor processability, which severely obstruct their application in practice. In this study, we develop a convenient top-down process for fabricating solution-processable covalent organic frameworks by introducing intermolecular hydrogen bonding and π-π interactions from ionic liquids. The bulk powders of imine-linked, azine-linked, and β -ketoenamine linked covalent organic frameworks can be dispersed homogeneously in optimal ionic liquid 1-methyl-3-octylimidazolium bromide after heat treatment. The resulting high-concentration colloids are utilized to create the covalent organic framework inks that can be directly printed onto the surface. Molecular dynamics simulations and the quantum mechanical calculations suggest that C‒H···π and π-π interaction between ionic liquid cations and covalent organic frameworks may promote the formation of colloidal solution. These findings offer a roadmap for preparing solution-processable covalent organic frameworks, enabling their practical applications. Covalent organic frameworks are generally not dispersible in common solvents resulting in the poor processability which limits their practical application. Here, the authors develop a top-down process to produce solution-processable covalent organic frameworks based on the assistance of ionic liquids by means of intermolecular hydrogen bonding and π-π interactions.

As one of the most attractive methods for the synthesis of ordered hierarchically porous crystalline materials, the soft-template method has not appeared in covalent organic frameworks (COFs) due to the incompatibility of surfactant self-assembly and guided crystallization process of COF precursors in the organic phase. Herein, we connect the soft templates to the COF backbone through ionic bonds, avoiding their crystallization incompatibilities, thus introducing an additional ordered arrangement of soft templates into the anionic microporous COFs. The ion exchange method is used to remove the templates while maintaining the high crystallinity of COFs, resulting in the construction of COFs with ordered hierarchically micropores/mesopores, herein named OHMMCOFs (OHMMCOF-1 and OHMMCOF-2). OHMMCOFs exhibit significantly enhanced functional group accessibility and faster mass transfer rate. The extrinsic porosity can be adjusted by changing the template length, concentration, and ratio. Cationic guanidine-based COFs (OHMMCOF-3) are also constructed using the same method, which verifies the scalability of the soft-template strategy. This work provides a path for constructing ordered and tunable extrinsic porosity in COFs with greatly improved mass transfer efficiency and functional group accessibility. The synthesis of covalent organic frameworks (COFs) by a soft-template methodology is challenging. Here, the authors attach the soft templates to the COFs backbone via ion bonds, avoiding crystallization incompatibilities and allowing subsequent removal of the template by ion exchange for enhanced U(VI)/Th(IV) adsorption performance.

As the radioactive iodine possessed volatility and diffusibility, it needed to be properly disposed in order to prevent environmental and health risks. Recently, nitrogen-rich covalent organic frameworks (COFs) were found to have high iodine adsorption capacity, but the unstable linkages limited their application. In this work, we synthesized an amine-linked COFs with nitrogen-rich melamine unit named TABN-COF. TABN-COF exhibited a strong affinity for iodine, with an adsorption capacity of up to 365 mg/g for I3− in aqueous phase. The ultra-strong stability of TABN-COF enabled it to maintain its crystallinity structure even after treatment with acids, bases, simulated seawater, reducing agents, and oxidizing agents, without compromising the removal rate of I3−. These characteristics made TABN-COF promising for the adsorption of I3− in complex marine systems.

High-rise buildings represent technological, urban, and life-style trends of the modern urban landscape, yet there are limited data regarding their embodied carbon and environmental impacts, particularly when compared to low- or mid-rise buildings. Given that the projected growth of the global urban population by 2050 requires cities with higher density and potentially a greater number of high-rise buildings, it is crucial to develop a clear understanding of the embodied carbon and environmental impacts of high-rise buildings. The primary structural materials used in high-rise buildings are reinforced concrete and structural steel. As of today, over 99% of tall buildings’ structures are built from those two materials. This article utilizes a building information modeling (BIM)-based life cycle assessment (LCA) in Revit and Tally to examine the embodied carbon and environmental impacts of an actual high-rise building structure case study in Chicago that uses a hybrid concrete steel structure. The results show that the embodied carbon and environmental impacts of the high-rise building structure are dominated by the impacts of the product stage in the building’s life cycle and by concrete being the main structural material. Specifically, this study reveals that concrete constitutes a substantial 91% share of the total mass of the building structure, with a 74% contribution to the life cycle global warming potential, 53% to the acidification potential, 74% to the eutrophication potential, 74% to the smog formation potential, and 68% to the non-renewable energy usage. On the other hand, steel accounts for 9% of the building’s structure mass, estimated to constitute 26% of the global warming potential, 47% of the acidification potential, 26% of the eutrophication potential, 26% of the smog formation potential, and 32% of the non-renewable energy usage.

The separation of radionuclides is critical for the sustainable development of nuclear energy. It is urgent to design and prepare functionalized materials for efficient radionuclides separation. Porous materials are considered excellent candidates for the separation of radionuclides under complex conditions due to their high specific surface areas, tunable pore structures and controllable functionalities. In this review, we summarized the design, preparation and functionalization of porous materials and their application for separation of radionuclides in the past five years, discussed the separation performance and analyzed the structure-activity relationship between various radionuclides and porous materials, and systematically clarified their characterization and mechanism of different type porous materials. We also introduced the detection, irradiation and chemical toxicity of different reflective radionuclides.

Today 55 percent of population in the world lives in urban areas which is expected to increase to 68 percent by the year 2050. In the cities, high-rise buildings as symbols of the modern cityscape are dominating the skylines, but the data to demonstrate their embodied energy and environmental impacts are scarce, compared to low- or mid-rise buildings. Reducing the embodied energy and environmental impacts of buildings is critical as about 42 percent of primary energy use and 39 percent of the global greenhouse gas (GHG) emissions come from the building sector. However, it is an overlooked area in embodied energy and environmental impacts of tall buildings. This doctoral research aims to investigate the effects of tall buildings on embodied energy and environmental impacts by using process-based life cycle assessment (LCA) methodology within Building Information Modelling (BIM) environment, which provides construction industry platform to incorporate sustainability information in architectural design. This doctoral research is carried out through a literature review on embodied energy of high-rise buildings. Current LCA methods of buildings are also discussed in the literature review. It then develops a framework for BIM-based assessment of the embodied energy and environmental impacts of tall buildings. To achieve that, a case study of tall reinforced concrete building is applied, by using ISO 14040 and 14044 guidelines with available database, Revit and Tally application in Revit. The author concentrates on embodied energy and environmental impacts of reinforced concrete tall buildings. Finally, the association between design and construction variables with embodied energy and environmental impacts is explored. This research will lead to significant contributions. A comprehensive study on embodied energy and environmental impacts of high-rise building will address a major gap in LCA literature. Researchers and environmental consultants can use the results of this research to create design tools to evaluate environmental impacts of high-rise buildings. Also, architects can use the results of this research to develop insight into the environmental performance of tall buildings in early design stage. Architects and engineers can also use the results to optimize tall building design for low embodied energy and environmental impacts. Finally, the results of this research will enable architects, engineers, planners, and policymakers develop more sustainable built environments.

Water inrush and mud burst disasters pose severe challenges to the safe and efficient construction of underground engineering. Water inflow prediction is closely related to drainage design, disaster prevention and control, and the safety of the surrounding ecological environment. Thus, assessing the water inflow accurately is of importance. This study proposes a Bayesian Optimization-Long Short-Term Memory (BOA-LSTM) recurrent neural network for predicting tunnel water inflow. The model is based on four input parameters, namely tunnel depth (H), groundwater level (h), rock quality designation (RQD), and water-richness (W), with water inflow (WI) as the single-output variable. The model first processes and analyzes the data, quantitatively characterizing the correlations between input parameters. The tunnel water inflow is predicted using the long short-term memory (LSTM) recurrent neural network, and the Bayesian optimization algorithm (BOA) is employed to select the hyperparameters of the LSTM, primarily including the number of hidden layer units, initial learning rate, and L2 regularization coefficient. The modeling process incorporates a five-fold cross-validation strategy for dataset partitioning, which effectively mitigates overfitting risks and enhances the model’s generalization capability. After a comprehensive comparison among a series of machine learning models, including a long short-term memory recurrent neural network (LSTM), random forest (RF), back propagation neural network (BP), extreme learning machine (ELM), radial basis function neural network (RBFNN), least squares support vector machine (LIBSVM), and convolutional neural network (CNN), BOA-LSTM performed excellently. The proposed BOA-LSTM model substantially surpasses the standard LSTM and other comparative models in tunnel water inflow prediction, demonstrating superior performance in both accuracy and generalization. Hence, it provides a reference basis for tunnel engineering water inflow prediction.

Reduction of soluble U(VI) to insoluble U(IV) based on semiconductor photocatalysts is a favored U(VI)-extraction method, because of its simplicity, environmental friendliness, and high efficiency. The key to implement this technology is the development of efficient photocatalysts with high activity and stability for sacrificial agents-free U(VI) photoreduction. Herein, we report a new type of CdS/covalent organic framework (COF) core-shell photocatalysts (CdS@COF-X, X = 5, 10, 15, and 20) with efficient chemisorption, enhanced carrier separation, and antiphotocorrosion ability for U(VI) photoreduction without additional sacrificial agents. The two-dimensional COF, formed by the polycondensation of 2,4,6-triformylphloroglucinol and 1,3,5-tris(4-aminophenyl)triazine, was selected to construct the hybrid materials due to its high chemical stability, matching band gaps and efficient chemisorption for U(VI). Remarkably, CdS@COF-10 realized a record high U(VI) extraction capacity of 1825.6 mg g−1 after 90 min. Moreover, the reduction ratio of uranium was up to 82.5%, and the product was identified as uranium dioxide (UO2) after reaction. Further mechanistic studies indicated that the COF shell not only provided chemisorption sites for U(VI) to decrease the activation energy of U(VI) reduction, but also formed a strong built-in electric field at the interface with the CdS core to promote the carrier separation. More importantly, for all CdS@COF-X, CdS-COF-10 with appropriate COF shell content balanced the crystallinity, interfacial contact integrity, light absorption of CdS core, and number of U(VI) chemisorption sites, achieving the highest carrier separation efficiency and U(VI) photoreduction performance.

Variant Sedum alfredii Hance ( V S. alfredii ) could simultaneously take up U and Th from water with the highest concentrations recorded as 1.84 × 10 4 and 6.72 × 10 3  mg/kg in the roots, respectively. Th stimulated U uptake by V S. alfredii roots at Th 10 (10 μM of Th), however, the opposite was observed at Th 100 (100 μM of Th). A similar result was found in the effect of U on the uptake of Th by V S. alfredii . Subcellular fractionation studies of V S. alfredii indicated that U and Th were mainly stored in cell wall fraction, and much less was found in organelle and soluble fractions. Chemical form examination results showed that water-soluble U and Th were the predominant chemical forms in this plant. Addition of the other radionuclide in aqueous solutions altered the concentration and percentage of U or Th in cell wall fraction and in water-soluble form, resulting in the change of the uptake capacity of U or Th by V S. alfredii roots. Comparing with single U or Th treatment, the plant cells revealed more swollen chloroplasts and enhanced thickening in cell walls under the U 100  + Th 100 treatment, as observed by TEM. Those results collectively displayed that V S. alfredii may be utilized as a potential plant to simultaneously remove U and Th from aqueous solutions (rhizofiltration).