Carbon dioxide (CO2), as the primary greenhouse gas in the atmosphere, triggers a series of environmental and energy related problems in the world. Therefore, there is an urgent need to develop ...multiple methods to capture and convert CO2 into useful chemical products, which can significantly improve the environment and promote sustainable development. Over the past several decades, metal‐organic frameworks (MOFs) have shown outstanding heterogeneous catalytic activity due in part to their high internal surface area and chemical functionalities. These properties and the ability to synthesize MOF platforms allow experiments to test structure‐function relationships for transforming CO2 into useful chemicals. Herein, recent developments are highlighted for MOFs participating as catalysts for the chemical fixation and photochemical reduction of CO2. Finally, opportunities and challenges facing MOF catalysts are discussed in this ongoing research area.
CO2 triggers a series of environmental and energy problems as the primary greenhouse gas in our daily life. MOFs (metal‐organic frameworks) are applied as outstanding heterogeneous catalysts for CO2 chemical transformations. A systematic overview of the development of MOF‐based catalysts for CO2 chemical transformations are reviewed, from the first example to the most recent publication.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
A majority of metal–organic frameworks (MOFs) fail to preserve their physical and chemical properties after exposure to acidic, neutral, or alkaline aqueous solutions, therefore limiting their ...practical applications in many areas. The strategy demonstrated herein is the design and synthesis of an organic ligand that behaves as a buffer to drastically boost the aqueous stability of a porous MOF (JUC‐1000), which maintains its structural integrity at low and high pH values. The local buffer environment resulting from the weak acid–base pairs of the custom‐designed organic ligand also greatly facilitates the performance of JUC‐1000 in the chemical fixation of carbon dioxide under ambient conditions, outperforming a series of benchmark catalysts.
A buffer strategy boosts the aqueous stability of a MOF over a broad range of pH values. The local buffer environment resulting from the weak acid–base pairs (green/blue bars on right of picture) of the custom‐designed organic ligand also greatly facilitates the performance of MOF in chemical fixation of carbon dioxide under ambient conditions.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
A versatile microporous zinc(II) MOF (1) with plentiful Lewis basic sites and open metal sites synchronously has been synthesized successfully. The resultant microporous material displays excellent ...selectivity adsorption for small gases. The IAST selectivity values for CO2/CH4, C2H6/CH4, CO2/N2, and C3H8/CH4 are 7, 21, 38, and 125 at 101 kPa and 298 K, respectively. 1 exhibits remarkably heterogeneous catalytic performance for acid–base one-pot reactions. Furthermore, 1 exhibits recyclable selective detectability for TNP. The results illustrate that 1 is a versatile material for selective gas adsorption, cooperative catalysis, and luminescent sensing.
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IJS, KILJ, NUK, PNG, UL, UM
Metal-organic frameworks (MOFs) are a rapidly growing class of hybrid materials with many multifunctional properties. The permanent porosity plays a central role in the functional properties. In ...particular, the luminescent MOFs with a permanent porosity have wide applications in guest species recognition and adsorption. In this contribution, we aim to develop tunable colors and white-light luminescence materials by the encapsulation of Ln(3+) species in microporous luminescent MOFs. A semi-rigid trivalent carboxylic acid 1,3,5-tri(4-carboxyphenoxy)benzene (H3TCPB) was selected as the organic building block, not only because it is suitable to construct microporous frameworks, but also by reason of its blue luminescent emission. Under solvothermal reactions, a microporous MOF material, Zn3(TCPB)2(H2O)2·2H2O·4DMF (JUC-113, JUC = Jilin University, China), was synthesized, which has a permanent porosity and emits blue light. According to three-primary colors, the guest luminescent species should be Tb(3+) and Eu(3+) owing to their distinctive colors (Tb(3+), green; Eu(3+), red). In addition, the luminescent properties of JUC-113 can be easily tuned by different combinations of the encapsulation amount of Tb(3+) and Eu(3+), obtaining white-light emission materials.
•Quantitative reconstruction of soil erosion, sediment transport and delta deposition.•Soil erosion intensity was weak before the late Holocene, and increased afterwards.•The sediment deposition and ...soil erosion intensity were synchronous.•Soil erosion was dominated by climate as natural process before the middle Holocene.•Soil erosion was accelerated by human activities in the late Holocene.
The Yellow River Basin is ideal for studying fluvial landscape evolution under climate change and human activities. Quantitative reconstruction of soil erosion, sediment transport, and delta deposition in the basin enhances understanding of the dynamic mechanisms of fluvial surface processes. This study reconstructs the spatial and temporal distribution of precipitation and vegetation cover based on geological profile records, paleoclimatic datasets, and historical documentation in the Yellow River basin during the Holocene. A landscape evolution model (Landlab) is introduced to simulate soil erosion and sediment deposition processes. Modeling results show that soil erosion intensity in the middle reaches of the Yellow River was weak during the early and middle Holocene. Since the late Holocene, soil erosion has increased due to vegetation degradation, as the climate became drier, but with more fluctuations. Since 2.0 ka (1 ka = 1,000 calibrated a B.P.), and especially since 1.0 ka, soil erosion in the middle reaches of the Yellow River increased rapidly due to strong human activity, with the intensity-six times higher than the average level before the late Holocene. Average sediment deposition thickness in the lower reach of the Yellow River (North China Plain) was about 2.4 m, and sediment volume was about 3.6 × 1011 m3. The deposition rate and soil erosion intensity showed synchronous changes during the Holocene. Since 2.0 ka, the sediment load and deposition rate have increased rapidly, to 6–10 times higher than in the early and middle Holocene. On this basis, the effects of climate change and human activities on the evolution of the fluvial landscape are discussed.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPUK, ZAGLJ, ZRSKP
Soil erosion, sediment transport, and delta deposition are of great importance to the evolution of fluvial landforms. In this study, we carry out a quantitative and comprehensive analysis to identify ...dynamic processes and mechanisms of soil erosion, fluvial plain deposition, and river delta formation in response to Holocene environmental changes over the past 10,000 years. In this investigation, the following results are achieved. First, spatial variations of the monsoon border (400 mm isohyet) resulted in dynamic changes in soil erosion on the Loess Plateau, sediment transportation downstream, and fluvial deposition on the plains and delta during the Holocene. Climate change and human activities played essential roles in variations of the plateau-plain-delta system during different periods. In the early Holocene, the number and scale of Neolithic cultural sites in the Yellow River basin increased. In the past 3000 years, human activities have strongly influenced and dominated environmental evolution in this region. Second, soil erosion was the critical contributor to the construction of the North China Plain. The Yellow River Delta provided the preliminary living environment where historical civilization in the Yellow River basin formed and developed, giving birth to the Yellow River civilization. Sediment discharge in the Loess Plateau was the primary source for river channel development and shaping of the river delta.
•To identify processes and mechanisms of the Holocene soil erosion, fluvial plain deposition, and river delta formation in the middle and lower reaches of the Yellow River.•Spatial variations of the monsoon border resulted in dynamic changes in soil erosion on the Loess Plateau, sediment transportation downstream, and fluvial deposition on the plains and delta during the Holocene.•Climate change and human activities played essential roles in variations of the plateau-plain-delta system during different periods.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPUK, ZAGLJ, ZRSKP
A bifunctional MOF (JUC-199) featuring dual functionality, open metal sites (Zn2+) and Lewis basic sites (-NH2), has been successfully synthesized using a custom-designed ligand. JUC-199 demonstrated ...good selective gas sorption behaviours with IAST selectivity values of 9, 30, 37 and 64 at 298 K and 101 kPa for CO2/CH4, CO2/N2, C2H6/CH4 and C2H4/CH4 respectively; surpassing those of most MOFs reported thus far. Moreover, JUC-199 can serve as a heterogeneous cascade catalyst to efficiently catalyse the tandem one-pot deacatalization-Knoevenagel condensation reaction.
The sophisticated control of surface wettability for target-specific applications has attracted widespread interest for use in a plethora of applications. Despite the recent advances in modification ...of non-porous materials, surface wettability control of porous materials, particularly single crystalline, remains undeveloped. Here we contribute a general method to impart amphiphobicity on single-crystalline porous materials as demonstrated by chemically coating the exterior of metal-organic framework (MOF) crystals with an amphiphobic surface. As amphiphobic porous materials, the resultant MOF crystals exhibit both superhydrophobicity and oleophobicity in addition to retaining high crystallinity and intact porosity. The chemical shielding effect resulting from the amphiphobicity of the MOFs is illustrated by their performances in water/organic vapour adsorption, as well as long-term ultrastability under highly humidified CO
environments and exceptional chemical stability in acid/base aqueous solutions. Our work thereby pioneers a perspective to protect crystalline porous materials under various chemical environments for numerous applications.
An azo-functionalized porous organic framework (denoted as JJU-1) was synthesized via FeCl3-promoted oxidative coupling polymerization. By virtue of a porous skeleton and a light/heat responsive azo ...functional group, this task-specific JJU-1 displays a reversible stimuli-responsive adsorption property triggered by UV irradiation and heat treatment. The initial Brunauer–Emmet–Teller (BET) surface area of this porous material is 467 m2 g–1. The CO2 sorption isotherms exhibit a slight decrease after UV irradiation because of the trans to cis conversion of the azo functional skeleton. It is worth mentioning that the responsive CO2 adsorption performance can be recycled for three cycles via alternating external stimuli, confirming the excellently reversible switchability of trans-to-cis isomerization and controllable CO2 adsorption.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Different proxies have been used to investigate Quaternary paleoclimate change. Here, we used weathering of calcium nodules in paleosols on China's Loess Plateau as a proxy for Quaternary ...paleoclimate changes to provide an alternative indicator of these changes. Paleosol and carbonate nodules were collected from Luochuan and Lantian counties in Shaanxi Province, China. We found that this approach allowed quantitative reconstruction of temperature, rainfall, soil mineral composition, and the effects of weathering and leaching. The changes in carbonate content in the loess and paleosol sequences were controlled by alternating dry and wet climatic conditions. Nodule formation conditions were directly affected by the leaching and migration of elements. The loess and paleosol sequences developed calcium nodules, and their formation was closely related to the rainfall and leaching characteristics of the paleoclimate. The paleoclimate and soil minerals affected the vegetation types and directly influenced changes in the soil. During formation of the calcium nodules, the surface vegetation evolved slowly, and the number of species and quantity of vegetation both decreased.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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