Reducing the anthropogenic CO
2 emissions from fossil resource combustion and human activities has become one of the major challenges we are facing today. Beyond those practical applications for the utilization of CO
2, such as the synthesis of salicylic acid, methanol, urea, NaHCO
3-Na
2CO
3 chemicals and recently developed polycarbonate synthesis, scientists are still seeking new materials and technologies for efficient capture, storage and conversion of CO
2 with consideration into reducing CO
2 emission at a large amount. Until now,
CO2 capture and utilization is not only an academic event but
a social and government guiding project
all over the world. The special issue in
Journal of Energy Chemistry is an
update of recent research works on the topic of
carbon capture storage and utilization (CCUS) which covers the material and technology innovations for CO
2 capture and utilization. Five reviews, two communications and seventeen research articles are included in this special issue. As a first step for limiting the
CO2 emission, efficient capture of CO
2 with a
cost-effective strategy, is likely to rely on new adsorbents and the development of technologies that can reduce energy consumption, especially for the separation of low concentrated
CO2 from coal-fired power plant flue gas and selective capture of CO
2 from
humid gases. CO
2 molecules are often preferred to be adsorbed in porous materials with high surface area and abundant sorption sites. The concept of molecular basket sorbent (MBS) for CO
2 capture has been proposed by Song et al. in this special issue. They use polyethylenimine (PEI) or polyethylene glycol (PEG) to reside in the mesopore structure of SBA-15, TUD-1 and fumed silica HS-5 materials to provide plenty of amine sites for CO
2 adsorption. Zhong et al. synthesize a type of 2D covalent triazine-based framework material (namely, CTF-DCBT) for efficient capture of CO
2. CTF-DCBT contains ultramicropore (6.5 Å) and high heteroatom contents (11.24 wt% of N and 12.61 wt% of S), which is responsible for the highly selective CO
2/N
2 and CO
2/CH
4 preferential adsorption. Porous carbon materials with well-developed heteroatom doped sites are widely examined as CO
2 adsorbents. In the work of Ahn et al., nitrogen-doped carbon materials are synthesized by the carbonization of a low-cost porous covalent triazine polymer, PCTP-3. The textural properties of the porous carbon materials are additionally activated by KOH, to form a narrow micropore size distribution. A type of porous carbon sphere with highly developed ultra-microporosity and uniform pore size is prepared by Zhou and Zhuo et al. These well-designed porous carbon materials on purpose are examined as excellent adsorbents with high CO
2 capture capacity and selectivity. Pfeiffer and co-workers systematically investigate the CO
2 chemisorption process on a series of alkaline pentalithium aluminate (β-Li
5AlO
4) based solid solution. With an addition of alkaline carbonate compound or iron exchange with the aluminum position into β-Li
5AlO
4, the CO
2 chemisorption enhances. CO
2 molecules are more likely to reside on the superficial position of those (modified) alkaline solid solution adsorbents. CO
2 capture by ionic liquids (ILs) has also attracted wide attention. In the contributions of Yu et al. and Sun et al., a series of ILs
monomers and ILs polymers (PILS) and a type of layered hybrids material containing ILs are prepared, respectively. Both the PILs and BMIMCl/LP layered hybrids are identified as efficient adsorbents with high CO
2 capture capacity. Zhang et al. select a series of [CnMIm][Tf
2N] ILs as physical CO
2 adsorbents and the adsorption condition is operated under a wide temperature and pressure range, which is appealing at higher temperature. Kanoh et al. examine the capacity and kinetics of CO
2 capture over K
2CO
3 adsorbent. In this work, a detailed study on the influence of temperature with changed moisture conditions and further insight into the NaHCO
3 formation mechanism has been carried out. Shi et al. employ a combination of WGS reaction and elevated-temperature pressure swing adsorption technology to deeply remove trace CO
2 and CO impurities to harvest high purity H
2 gas. The technology is based on potassium promoted hydrotalcite adsorbents, which can reduce the residual CO
2 concentration to 3.5 ppm after 12 h of temperature swing operation at 450 °C. In the search of highly efficient CO
2 adsorbents under different real working conditions, Wang et al. and Ahn et al. critically review the development of molten salts modified MgO-based adsorbents and Amine-functionalized silica composite materials, respectively. Molten salts-modified MgO-based adsorbents show their advantages in the high adsorption capacity (the highest CO
2 capture capacity of 12.9 mmol g
-1 as reported), low cost, wide availability and suitable for the CO
2 capture at intermediate temperature range (200
–400 °C). Amine-functionalized silica composite materials are promising candidates for post-combustion CO
2 capture from low CO
2 concentrated flue gases. They show the advantages of excellent CO
2 uptake, selectivity, less sensitive to moisture and facile for the regeneration. Besides CO
2 capture, considerations about the recycling and utilization of CO
2 when using CO
2 as the abundant carbon resource are in progress to accomplish the challenging task of
carbon neutral process. Direct catalytic conversion of CO
2 to value added chemicals or fuels has aroused great attention in both academic and commercial fields. Hydrogenation of CO
2 to formic acid and CO and other carbonaceous products in the lower carbon chemical valence state has been widely studied. Jin et al. investigate the auto-catalytic role of Zn/ZnO interface, which is formed in-situ during the reaction, in the transformation of CO
2 to formic acid in the water medium. They also provide an overview of the current advances in research of highly efficient reduction of CO
2 or NaHCO
3 into formic acid/formate by in-situ hydrogen from water dissociation with a metal/metal oxide redox cycle under mild hydrothermal condition. In the review made by Huang et al., the catalytic performance of CO
2-to-CO conversion and recent updates in designing of heterogeneous catalysts with high CO product selectivity and high temperature robustness are
specifically elaborated. In the contribution of Chen et al.,
Ca(OH)2 and 10% Ni/ZrO
2 are introduced in the biomass conversion processes of cellulose. Ca(OH)
2 greatly enhances the H
2 production rate with a yield of 36.4%, while the in-situ reforming of light gases and carbon capture processes significantly suppress the CO
2 formation. Ma et al. delicately design a dual active center containing Salen-Cu(II)@MIL-101(Cr) via the “ship in a bottle” approach, which is developed as the active catalyst for the synthesis of propylene carbonate from CO
2 and propylene oxide. The sorption enhanced methane reforming process of CO
2 has been studied by Pfeiffer et al. and Courson et al., by using CaO-NiO mixed oxide and CaO-Ca
12Al
14O
33, respectively. The studied catalyst systems show excellent chemical stability in obtaining syngas (H
2 + CO) with high CH
4 conversion and H
2 yield. Smart conversion processes such as chemical looping and mineral carbonation of CO
2 are capable of utilizing CO
2 at large quantities. Haider et al. describe the use of copper(II) oxides in combination with limestone in the form of a mechanical pelletizer as the oxygen carriers in the chemical looping processes. The oxygen carriers exhibit an enhanced crushing strength with high CO yield. Li et al. report the mineral carbonation processes of blast furnace slag with
intention to reduce substantial CO
2 emission at large quantities. As a recyclable extractant, (NH
4)
2SO
4, is used to extract calcium and magnesium from blast furnace slag by using low-temperature roasting to fix CO
2 through aqueous carbonation. Alternatively, electrochemical reduction of
CO2 provides another promising way in reducing CO
2 emission, which can be delivered in the form of renewable energy. Co-electrolysis of CO
2 and H
2O using high-temperature solid oxide electrolysis cells (SOECs) into valuable chemicals is the topic of contribution made by Wang and Bao et al. The review discusses the so far cathode material development, the alternative cathode materials preparation strategies and the possible cathode reaction mechanism for CO
2/H
2O electrolysis. Different reaction modes of the CO
2/H
2O co-electrolysis in SOECs are summarized to offer new strategies to enhance the CO
2 conversion. Kang et al. report a nitrogen doped tin oxide material with enhanced Faradaic efficiency (90%) for CO
2 electro-reduction to formate, which also shows sulfur tolerance. The combined catalyst structure of partially reduced metallic tin and N-doped tin oxide (Sn/N-SnO
2) is identified as the key for CO
2 to formate electro-reduction. In summary,
all these high quality works provided by the outstanding contributions in this highly attentive research area of CCUS will render this special issue to contribute a broad vision for the future research activities. Finally, we would like to express our sincere thanks to the reviewers and the editors for giving your time and expertise to review the papers and facilitate the publication of this issue.
