Presently, excessive carbon dioxide emissions represent a critical environmental challenge. Thus, urgent efforts are required to develop environmentally friendly and low-energy technologies for carbon dioxide treatment. In this case, membrane separation technology stands out as a promising avenue for CO₂ separation, with selective membrane materials of high permeability playing a pivotal role in this process. Herein, we categorize CO₂ separation membranes into three groups: inorganic membranes, organic membranes, and emerging membranes. Moreover, representative high-performance membranes are introduced and their synthesis methods, gas separation performances, and applications are examined. Furthermore, a brief analysis of the challenges encountered by carbon dioxide separation membrane materials is provided together with a discussion on the future research direction. It is expected that this review will provide some potential insights and guidance for the future development of CO₂ separation membranes, which can promote their development.

Cadmium is a heavy metal which exists widely in industrial and agricultural production and can induce a variety of diseases in organisms.

Low-viscosity slickwater fracturing fluids are a crucial technology for the commercial development of shallow shale gas. However, in deep shale gas formations with high pressure, a higher sand concentration is required to support fractures. Linear gel fracturing fluids and crosslinked gel fracturing fluids have a strong sand-carrying capacity, but the drag reduction effect is poor, and it needs to be pre-prepared to decrease the fracturing cost. Slick water fracturing fluids have a strong drag reduction effect and low cost, but their sand-carrying capacity is poor and the fracturing fluid sand ratio is low. The research and development of viscous slick water fracturing fluids solves this problem. It can be switched on-line between a low-viscosity slick water fracturing fluid and high-viscosity weak gel fracturing fluid, which significantly reduces the cost of single-well fracturing. A polyacrylamide drag reducer is the core additive of slick water fracturing fluids. By adjusting its concentration, the control of the on-line viscosity of fracturing fluid can be realized, that is, ‘low viscosity for drag reduction, high viscosity for sand-carrying’. Therefore, this article introduces the research and application status of a linear gel fracturing fluid, crosslinked gel fracturing fluid, and slick water fracturing fluid for deep shale gas reservoirs, and focuses on the research status of a viscous slick water fracturing fluid and viscosity-controllable polyacrylamide drag reducer, with the aim of providing valuable insights for the research on water-based fracturing fluids in the stimulation of deep shale gas reservoirs.

With the gradual depletion of oil resources, it is urgent to vigorously develop unconventional and renewable energy sources. As an unconventional resource with abundant resources, the rational and efficient development of oil shale is of great significance to alleviating the national energy crisis. The main methods of oil shale development are surface dry distillation and in situ transformation. In situ catalytic conversion technology, as an emerging mining method, has the potential to improve efficiency, reduce costs, and environmental impact and is an important direction for future oil shale development. As a key component in the in situ conversion process, catalysts play a crucial role in the rate, selectivity, and product quality of the reaction. However, the research on oil shale pyrolysis catalysts is still in the laboratory stage and is difficult to translate into practical applications. Therefore, this paper reviews recent progress of catalyst research in the in situ catalytic conversion of oil shale, including the types, design principles, and reaction mechanisms of catalysts, and looks forward to the future development direction. It provides a certain reference for the discovery of new catalysts that can improve yield and reduce environmental pollution in the process of oil shale extraction and also provides a valuable technical reference for the green development and utilization of unconventional and strategic alternative energy sources in the world and the transformation and sustainable development of the global energy structure.

Hyperbranched polymer is a kind of polymer with a three-dimensional structure, which contains a highly branched structure and a large number of modified terminal functional groups. The desired properties can be obtained by modifying the active end groups appropriately. Hyperbranched polymers have been successfully used in the development of oilfield chemicals due to their excellent properties of solubility, rheology, temperature resistance, and salt resistance. Therefore, the application of hyperbranched polymer is helpful to the efficient development of oilfields. In this paper, the synthesis methods of hyperbranched polymers are reviewed. The advantages and disadvantages of different synthesis methods are analyzed. Furthermore, the research progress of hyperbranched polymers in oilfield chemistry is systematically described, and the advantages and existing problems of their application in polymer flooding as oil displacement agents, demulsification of crude oil, clay hydration expansion inhibition, and shale inhibition are discussed. Finally, the application prospect of hyperbranched polymer in drilling chemistry, oil recovery chemistry, and gathering and transportation chemistry is forecasted, which is expected to help the popularization and application of hyperbranched polymer in oilfields.