Abstract Electrochemically reducing CO 2 to more reduced chemical species is a promising way that not only enables the conversion of intermittent energy resources to stable fuels, but also helps to build a closed-loop anthropogenic carbon cycle. Among various electrocatalysts for electrochemical CO 2 reduction, multifunctional metal–organic frameworks (MOFs) have been employed as highly efficient and selective heterogeneous electrocatalysts due to their ultrahigh porosity and topologically diverse structures. Up to now, great progress has been achieved in the design and synthesis of highly active and selective MOF-related catalysts for electrochemical CO 2 reduction reaction (CO 2 RR), and their corresponding reaction mechanisms have been thoroughly studied. In this review, we summarize the recent progress of applying MOFs and their derivatives in CO 2 RR, with a focus on the design strategies for electrocatalysts and electrolyzers. We first discussed the reaction mechanisms for different CO 2 RR products and introduced the commonly applied electrolyzer configurations in the current CO 2 RR system. Then, an overview of several categories of products (CO, HCOOH, CH 4 , CH 3 OH, and multi-carbon chemicals) generated from MOFs or their derivatives via CO 2 RR was discussed. Finally, we offer some insights and perspectives for the future development of MOFs and their derivatives in electrochemical CO 2 reduction. We aim to provide new insights into this field and further guide future research for large-scale applications.
In the last two decades, organic field-effect transistors (OFETs) have garnered increasing attention from the scientific and industrial communities. The performance of OFETs can be evaluated based on three factors: the charge transport mobility (μ), threshold voltage (Vth), and current on/off ratio (Ion/off). To enhance μ, numerous studies have concentrated on optimizing charge transport within the semiconductor layer. These efforts include: (i) extending π-conjugation, enhancing molecular planarity, and optimizing donor–acceptor structures to improve charge transport within individual molecules; and (ii) promoting strong aggregation, achieving well-ordered structures, and reducing molecular distances to enhance charge transport between molecules. In order to obtain a high charge transport mobility, the charge injection from the electrodes into the semiconductor layer is also important. Since a suitable frontier molecular orbitals’ level could align with the work function of the electrodes, in turn forming an Ohmic contact at the interface. OFETs are classified into p-type (hole transport), n-type (electron transport), and ambipolar-type (both hole and electron transport) based on their charge transport characteristics. As of now, the majority of reported conjugated materials are of the p-type semiconductor category, with research on n-type or ambipolar conjugated materials lagging significantly behind. This review introduces the molecular design concept for enhancing charge carrier mobility, addressing both within the semiconductor layer and charge injection aspects. Additionally, the process of designing or converting the semiconductor type is summarized. Lastly, this review discusses potential trends in evolution and challenges and provides an outlook; the ultimate objective is to outline a theoretical framework for designing high-performance organic semiconductors that can advance the development of OFET applications.
CH4–CO2 replacement technology has broad application prospects in reducing CO2 emission and developing natural gas hydrate (NGH) resources. It is of great significance to study the mechanism of CH4–CO2 replacement. In this paper, the effect of H2O on CH4–CO2 displacement behavior is studied by molecular dynamics (MD) simulation and quantum mechanics calculation. The interactions between the host and guest in cages of CH4 hydrate are calculated using the symmetry-adapted perturbation theory method. The contribution of physical components of binding energy can be determined. The result indicates that the electrostatic interaction of H2O–H2O and H2O–gas is a key factor of the CH4–CO2 replacement mechanism. Additionally, the microconfigurations and microstructure properties are analyzed by MD simulation in the systems containing a gas layer (CO2 or CH4) and a CH4 hydrate layer. The results showed that the movement and the arrangement of H2O molecules influence the hydrate structure due to the interaction of H2O–gas during the replacement process. The molecular simulation suggests that the change of electrostatic interaction with H2O molecules could improve the CH4–CO2 replacement efficiency, which can be favorable for the investigation of CH4 replacement technology in NGH with CO2 injection.
According to various river functions,water demands for eco-environment are classified into four parts: basic ecological water demand by rivers,water demand of pollution prevention,water demand of river water surface evaporation,water demand of transporting sand.In order to achieve the aim of various river functions,different kinds of calculation methods for water demand of river eco-environment are discussed.Based on this,principles and methods for determining the reasonable amount of river eco-environment and corresponding threshold are proposed,and index and standard of river health assessment are also introduced.It offers a theoretical basis for assessment of river health,and it is important to enhance ability of river integrated management.
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