Superior adsorption of 3D nanoporous architectures for Ni(ii) ions adsorption using polyvinyl alcohol as cross-linking agent and adsorption conveyor

In this study, we report a large-scale and low cost approach for the synthesis of three-dimensional (3D) polyvinyl alcohol/carbon nanotubes nanoporous architecture using self-assembly method. Polyvinyl alcohol, serving as a cross-linking agent and adsorption conveyor, could effectively interconnect carbon nanotubes sequentially and also effectively store Ni(ii) ions. An outstanding adsorption of 225.6 mg g⁻¹ was achieved for 3D nanoporous structure, which was 18-fold more than that for carbon nanotube powders and much higher than that for other sorbents reported in literature. In addition, it was found that 3D nanoporous architectures remained intact after adsorption, which could recollect resources and avoid carbon nanotube leakage into water. Therefore, the designed 3D nanoporous architectures have a good potential application in environmental protection.

In this study, we report a large-scale and low cost approach for the synthesis of three-dimensional (3D) polyvinyl alcohol/carbon nanotubes nanoporous architecture using self-assembly method.     

Advantages,limitations, and future suggestions in studying graphene-based desalination membranes

The potential of novel 2D carbon materials such as nanoporous single-layer graphene and multilayer graphene oxide membranes is based on their possible advantages such as high water permeability, high selectivity capable of rejecting monovalent ions, with high salt rejection, reduced fouling, and high chemical and physical stability. Here we review how the field has advanced in the study of their performances in various desalination approaches such as reverse osmosis, forward osmosis, nanofiltration, membrane distillation, and solar water purification. The research on making high-performance graphene membranes which started with reverse osmosis applications is seemingly evolving towards other directions.

The potential advantages of novel 2D carbon materials are high water permeability, high selectivity capable of rejecting monovalent ions, with high salt rejection, reduced fouling, and high chemical and physical stability.     

Synthesis of polysubstituted arenes through organocatalytic benzannulation

Polysubstituted arenes serve as ubiquitous structural cores of aromatic compounds with significant applications in chemistry, biological science, and materials science. Among all the synthetic approaches toward these highly functionalized arenes, organocatalytic benzannulation represents one of the most efficient and versatile transformations in the assembly of structurally diverse arene architectures under mild conditions with exceptional chemo-, regio- or stereoselectivities. Thus, the development of new benzannulation reactions through organocatalysis has attracted much attention in the past ten years. This review systemically presents recent advances in the organocatalytic benzannulation strategies, categorized as follows: (1) Brønsted acid-catalysis, (2) secondary amine catalysis, (3) primary amine catalysis, (4) tertiary amine catalysis, (5) tertiary phosphine catalysis, and (6) N-heterocyclic carbene catalysis. Each part is further classified into several types according to the number of carbon atoms contributed by different synthons participating in the cyclization reaction. The reaction mechanisms involved in different benzannulation strategies were highlighted.

Organocatalytic benzannulation represents one of the most efficient transformations for assembling polysubstituted arenes, this review presents recent advances in organocatalytic benzannulation strategies to construct functionalized benzenes.     

Bifunctional acid–base mesoporous silica@aqueous miscible organic-layered double hydroxides

A facile method for the synthesis of a series of mesoporous silica nanoporous (MSN) aqueous miscible organic layered double hydroxide core@shell nanocomposites using MCM-41, Al-MCM-41, SBA-15, and MCM-48 as the core is reported. These materials exhibit hierarchical morphologies with high surface areas and good porosity. Chemically, these materials offer controllable bifunctional basicity and acidity.

Core@shell materials which exhibit hierarchical morphology with ultra high surface area and controllable pore size and structure have been synthesised.     

Nitrogen-decorated,porous carbons derived from waste cow manure as efficient catalysts for the selective capture and conversion of CO2

The catalytic conversion of CO₂ is a promising solution to the greenhouse effect and simultaneously recycles the carbon sources to produce high value-added chemicals. Herein, we demonstrated a class of nanoporous carbons, which were synthesized by the direct carbonization of bio-waste cow manure, followed by activation with KOH and NaNH₂. Various characterizations indicate that the resultant nanoporous carbons have abundant nanopores and nitrogen sites. As a result, their performances for the capture and catalytic conversion of CO₂ were investigated. The synthesized nanoporous carbons exhibited superior properties for the selective capture and catalytic cycloaddition of CO₂ to propylene oxide as compared to various solid materials.

Nitrogen-doped, hierarchically porous carbons were prepared by the activation of waste cow manure at 600 °C, which acted as efficient catalysts for the highly selective capture and conversion of CO₂ into valuable chemicals.     

A review of modification of carbon electrode material in capacitive deionization

Capacitive deionization (CDI) technology has attracted wide attention since its advent and is considered as one of the most promising technologies in the field of desalination and ion recycling. It is constructed with an electric field by applying a low voltage of direct-current to make ions migrate directionally in solution to achieve the purpose of ion separation and removal. The performance of CDI is heavily dependent on the electrode material. Carbon is widely used as CDI electrode material because of its lower price and better stability. To enhance the adsorption capacity, extensive research efforts have been made for the modification of carbon material. In this review, we enumerate and analyze four modification methods of carbon material including element doping, metal oxide modification, chemical treatment and surface coating. The influence of each modification method on CDI performance is concluded in the perspective mechanism and some constructive advice is put forward on how to effectively enhance the performance of CDI by the decoration of carbon materials.

The modification methods of carbon material and their effect on the CDI performance were reviewed.     

Hydrophilic polymer-stabilized porous composite membrane for water evaporation and solar desalination

Solar steam generation is considered an effective and sustainable method for addressing freshwater shortages. However, several challenges to developing photothermal materials and improving evaporation performance currently exist. Herein, we designed a hydrophilic evaporator with double-layer structure by combining a hydrophilic polymer with three-dimensional porous carbon nanotube beads on a glass microfiber membrane. Poly(methacrylic acid) acted as a binder to stabilize the carbon-based photothermal layer along with continuously pumped water. The assembled carbon nanotube beads with porous structures not only harvested and converted light to heat but also provided available channels for fast vapor diffusion. An artificial tree evaporation configuration can effectively localize heat on the photothermal layer, which endowed the evaporator with a high evaporation rate of 1.62 kg m⁻² h⁻¹ with a solar-to-vapor energy conversion efficiency of 87% under 1 sun illumination. Meanwhile, excellent desalination performance and stable recycling test made the evaporator have great potential in practical applications.

A polymer-stabilized interfacial evaporator was designed with a porous structure, and exhibited excellent water evaporation and solar desalination performance.     

Facile synthesis of high-surface-area nanoporous carbon from biomass resources and its application in supercapacitors

It is critical for nanoporous carbons to have a large surface area, and low cost and be readily available for challenging energy and environmental issues. The pursuit of all three characteristics, particularly large surface area, is a formidable challenge because traditional methods to produce porous carbon materials with a high surface area are complicated and expensive, frequently resulting in pollution (commonly from the activation process). Here we report a facile method to synthesize nanoporous carbon materials with a high surface area of up to 1234 m² g⁻¹ and an average pore diameter of 0.88 nm through a simple carbonization procedure with carefully selected carbon precursors (biomass material) and carbonization conditions. It is the high surface area that leads to a high capacitance (up to 213 F g⁻¹ at 0.1 A g⁻¹) and a stable cycle performance (6.6% loss over 12 000 cycles) as shown in a three-electrode cell. Furthermore, the high capacitance (107 F g⁻¹ at 0.1 A g⁻¹) can be obtained in a supercapacitor device. This facile approach may open a door for the preparation of high surface area porous carbons for energy storage.

High-surface-area nanoporous carbon is obtained by direct pyrolysis of biomass resources without an activation process. An electrochemical test shows high capacitance.     

Synthesis of oxygen functionalized carbon nanotubes and their application for selective catalytic reduction of NOx with NH3

Oxygen functionalized carbon nanotubes synthesized by surface acid treatment were used to improve the dispersion properties of active materials for catalysis. Carbon nanotubes have gained attention as a support for active materials due to their high specific surface areas (400–700 m² g⁻¹) and chemical stability. However, the lack of surface functionality causes poor dispersion of active materials on carbon nanotube supports. In this study, oxygen functional groups were prepared on the surface of carbon nanotubes as anchoring sites for decoration with catalytic nanoparticles. The oxygen functional groups were prepared through a chemical acid treatment using sulfuric acid and nitric acid, and the amount of functional groups was controlled by the reaction time. Vanadium, tungsten, and titanium oxides as catalytic materials were dispersed using an impregnation method on the synthesized carbon nanotube surfaces. Due to the high density of oxygen functional groups, the catalytic nanoparticles were well dispersed and reduced in size on the surface of the carbon nanotube supports. The selective catalytic reduction catalyst with the oxygen functionalized carbon nanotube support exhibited enhanced NO_x removal efficiency of over 90% at 350–380 °C which is the general operating temperature range of catalysis in power plants.

Oxygen functionalized carbon nanotubes synthesized by surface acid treatment were used to improve the dispersion properties of active materials for catalysis.     

Recent advances in metal-free heteroatom-doped carbon heterogonous catalysts

The development of cost-effective, efficient, and novel catalytic systems is always an important topic for heterogeneous catalysis from academia and industrial points of view. Heteroatom-doped carbon materials have gained more and more attention as effective heterogeneous catalysts to replace metal-based catalysts, because of their excellent physicochemical properties, outstanding structure characteristics, environmental compatibility, low cost, inexhaustible resources, and low energy consumption. Doping of heteroatoms can tailor the properties of carbons for different utilizations of interest. In comparison to pure carbon catalysts, these catalysts demonstrate superior catalytic activity in many organic reactions. This review highlights the most recent progress in synthetic strategies to fabricate metal-free heteroatom-doped carbon catalysts including single and multiple heteroatom-doped carbons and the catalytic applications of these fascinating materials in various organic transformations such as oxidation, hydrogenation, hydrochlorination, dehydrogenation, etc.

Recent advances in metal-free heteroatom-doped carbon heterogeneous catalysts including the preparation methods and their catalytic applications in various organic reactions have been reported.     

Low voltage operation of a silver/silver chloride battery with high desalination capacity in seawater

Technologies for the effective and energy efficient removal of salt from saline media for advanced water remediation are in high demand. Capacitive deionization using carbon electrodes is limited to highly diluted salt water. Our work demonstrates the high desalination performance of the silver/silver chloride conversion reaction by a chloride ion rocking-chair desalination mechanism. Silver nanoparticles are used as positive electrodes while their chlorination into AgCl particles produces the negative electrode in such a combination that enables a very low cell voltage of only Δ200 mV. We used a chloride-ion desalination cell with two flow channels separated by a polymeric cation exchange membrane. The optimized electrode paring between Ag and AgCl achieves a low energy consumption of 2.5 kT per ion when performing treatment with highly saline feed (600 mM NaCl). The cell affords a stable desalination capacity of 115 mg g⁻¹ at a charge efficiency of 98%. This performance aligns with a charge capacity of 110 mA h g⁻¹.

The silver/silver chloride conversion reaction allows for a high desalination capacity of saline media with high molar strength.     

Decoration of silver nanoparticles on nitrogen-doped nanoporous carbon derived from zeolitic imidazole framework-8 (ZIF-8) via in situ auto-reduction

We discovered an in situ auto-reduction method to embed silver nanoparticles onto a nanoporous carbon (NC) derived from the zeolitic imidazole framework-8 (ZIF-8), without any requirement of the reducing agents. The detailed analysis demonstrated the formation of Ag NPs by the replacement of the metallic Zn residue in the NC with Ag ions. The synthesized Ag@NC exhibited a superior catalytic activity toward the reduction reaction of 4-nitrophenol into 4-aminophenol.

Unremoved metal residue and no utilization of reducing agent could be applied for synthesizing metal-supported catalyst.     

Nanoporous foam fabricated by dealloying AgAl thin film through supercritical fluid corrosion

In this research, nanoporous silver foams are fabricated through dealloying Ag₃₅Al₆₅ (as atomic percentage, at%) thin films in supercritical (SC) carbon dioxide. The supercritical CO₂ is mixed with either HCl, water or H₂C₂O₄ aqueous solution as the solute in the reaction chamber. Due to the low tension of the supercritical fluid, under the best operating conditions, the surface area of the as-dealloyed Ag₃₅Al₆₅ can reach 4.6 m² g⁻¹, and the porosity volume fraction value can reach 74%, with a smallest average pore size of around 75 nm. In an optimum supercritical CO₂ environment, a lower chemical concentration can be applied and it can take less time to form a uniform nanoporous structure.

In this research, nanoporous silver foams are fabricated through dealloying Ag₃₅Al₆₅ (as atomic percentage, at%) thin films in supercritical (SC) carbon dioxide.     

Zeolitic imidazolate framework (ZIF)-derived porous carbon materials for supercapacitors: an overview

The present analysis focuses on the synthetic methods used for the application of supercapacitors with various mysterious architectures derived from zeolitic imidazolate frameworks (ZIFs). ZIFs represent an emerging and unique class of metal–organic frameworks with structures similar to conventional aluminosilicate zeolites, consisting of imidazolate linkers and metal ions. Their intrinsic porous properties, robust functionalities, and excellent thermal and chemical stabilities have resulted in a wide range of potential applications for various ZIF materials. In this rapidly expanding area, energetic research activities have emerged in the past few years, ranging from synthesis approaches to attractive applications of ZIFs. In this analysis, the development of high-performance supercapacitor electrodes and recent strategies to produce them, including the synthesis of various heterostructures and nanostructures, are analyzed and summarized. This analysis goes via the ingenuity of modern science when it comes to these nanoarchitecture electrodes. Despite these significant achievements, it is still difficult to accurately monitor the morphologies of materials derived from metal–organic frameworks (MOFs) because the induction force during structural transformations at elevated temperatures is in high demand. It is also desirable to achieve the direct synthesis of highly functionalized nanosized materials derived from zeolitic imidazolate frameworks (ZIFs) and the growth of nanoporous structures based on ZIFs encoded in specific substrates for the construction of active materials with a high surface area suitable for electrochemical applications. The latest improvements in this field of supercapacitors with materials formed from ZIFs as electrodes using ZIFs as templates or precursors are discussed in this review. Also, the possibility of usable materials derived from ZIFs for both existing and emerging energy storage technologies is discussed.

The present analysis focuses on the synthetic methods used for the application of supercapacitors with various mysterious architectures derived from zeolitic imidazolate frameworks (ZIFs).     

A methodological review on material growth and synthesis of solar-driven water splitting photoelectrochemical cells

As a renewable and sustainable energy source and an alternative to fossil fuels, solar-driven water splitting with photoelectrochemical (PEC) cell is a promising approach to obtain hydrogen fuel with its near-zero carbon emission pathway by transforming incident sunlight, the most abundant energy source. Because of its importance and future prospects, a number of architectures with their own features have been formed by various synthesis and growth methods. Because the materials themselves are one of the most dominant components, they determine the solar-to-hydrogen efficiency of the PEC cells. Thus, several representative PEC cells were reviewed by categorizing them as per synthesis and/or growth methods such as physical vapor deposition, chemical vapor deposition, electrochemical deposition, etc. This review provides researchers with an overview and acts as a guide for research on solar-driven water splitting PEC cells.

Solar-driven PEC cell is a promising approach to obtain hydrogen with near-zero carbon emission pathway. In this article, PEC cell was reviewed as per growth/synthesis methods. This review provides an overview and a guide for research on PEC cell.     

Self-template construction of nanoporous carbon nanorods from a metal–organic framework for supercapacitor electrodes

The morphologies and structures of nanostructured carbons generally influence their catalysis, electrochemical performance and adsorption properties. Metal–organic framework (MOF) nanocrystals usually have various morphologies, and can be considered as a template to construct nanostructured carbons with shaped nanocubes, nanorods, and hollow particles by thermal transformation. However, thermal carbonization of MOFs usually leads to collapse of MOF structures. Here, we report shape-preserved carbons (termed as CNRods) by thermal transformation of nickel catecholate framework (Ni-CAT) nanorods. Supercapacitors of CNRods treated at 800 °C were demonstrated to have enhanced performance due to their structural features that facilitate electron conduction and ion transport as well as abundant O content benefiting the wettability of the carbon materials. This may provide a potential way to explore novel carbon materials for supercapacitors with controllable morphologies and high capacitive performance.

The Ni-CAT-derived porous carbon materials at 800 °C remain regular with a rod-like morphology and exhibit enhanced capacitive performance.     

Cheap,facile, and upscalable activated carbon-based photothermal layers for solar steam generation

Solar-to-steam generation characterized by nanostructured photothermal materials and interfacial heating is developed based on various carbon nanostructures such as graphene, reduced graphene oxide, CNT, or their combinations. However, multiple and sophisticated synthetic steps are required to generate macroscopic porosity in photothermal devices for the efficient mass transport of water and generated steam. Additionally, the fabrication of photothermal layers on a practical scale constitutes the main hurdle for real applications toward solar-driven desalination. Herein, we report on the development of highly efficient photothermal layers with a commercially available low-cost material, activated carbon (AC), by using facile filtration and spray coating methods, which lead to the generation of intraparticle porous structure without any additional processing. The AC-based photothermal layers generated 1.17 kg m⁻² h⁻¹ of steam under 1 sun, and 4.7 wt% of polyethyleneimine coating on AC enhanced steam generation by 8.5% under 1 sun, corresponding to 1.27 kg m⁻² h⁻¹ of the water evaporation rate and 85.66% of the photothermal conversion efficiency. This was due to improvements in light absorption and water uptake properties with the additional advantage of mechanical robustness. The outdoor solar-to-steam generation test with the spray-coated A4-sized photothermal layer in conjunction with the desalination test demonstrated the potential for practical desalination application with upscalability.

Highly efficient photothermal layers were developed based on a commercially available low-cost material, activated carbon, which demonstrates the potential for practical desalination application with upscalability.     

Facile synthesis of hierarchically porous carbonaceous materials derived from olefin/aldehyde precursors using silica as templates

Porous carbon is exceptionally useful, but it remains a great challenge to develop a facile route to prepare porous carbon materials with hierarchical structure and enhanced porosity. This work demonstrates a novel synthetic pathway for hierarchical carbonaceous materials (HCM) using isobutene and formaldehyde as carbon precursors via silica templates impregnated with phosphorus. Different from the traditional nanocasting method, the formation of the carbon structure is caused by heavy coke deposits on the solid catalyst in the course of the olefin/aldehyde vapor reaction. The coke-derived carbonaceous materials indicated by transmission electron microscopy (TEM) and nitrogen adsorption–desorption measurement are hierarchically mesoporous structures with a large surface area (971 m² g⁻¹) and pore volume (1.91 cm³ g⁻¹). We have demonstrated for the first time that the olefin/aldehyde reaction may provide a convenient route to develop a porous carbon texture. The newly developed method may lead to porous carbon having scientific and technological importance in adsorption and catalysis applications.

This work presents a novel procedure to synthesize hierarchically porous carbonaceous materials by coke formation.     

Ion-selective asymmetric carbon electrodes for enhanced capacitive deionization

With the development of capacitive deionization technology, charge efficiency and electrosorption capacity have become some of the biggest technical bottlenecks. Asymmetric activated carbon electrodes with ion-selective functional groups inspired by membrane capacitive deionization were developed to conquer these issues. The deionization capacity increased from 11.0 mg g⁻¹ to 23.2 mg g⁻¹, and the charge efficiency increased from 0.54 to 0.84, due to ion-selective functional groups minimizing the co-ion effect. The charge efficiency and electrosorption capacity resulting from better wettability of these electrodes are effectively enhanced by grafting ion-selective functional groups, which are propitious to ion movement. In addition, asymmetric deionization capacitors show better cycling stability and higher desalination rates. These experimental results have demonstrated that the modification of the ion-selective (oxygen-containing) functional groups on the surfaces of activated carbon could greatly minimize the co-ion effects and increase the salt removal from the solution. These results have indicated that the ion-selective asymmetric carbon electrodes can promote well the development of deionization capacitors for practical desalination.

Ion-selective asymmetric carbon electrodes are developed for capacitive deionization to minimize the co-ion effects.     

Electronic and optical properties of BxCyNz hybrid α-graphynes

Hybrid two-dimensional (2D) materials composed of carbon, boron, and nitrogen constitute a hot topic of research, as their flexible composition allows for tunable properties. However, while graphene-like hybrid lattices have been well characterized, systematic investigations are lacking for various 2D materials. Hence, in the present contribution, we employ first-principles calculations to investigate the structural, electronic and optical properties of what we call B_xC_yN_z hybrid α-graphynes. We considered eleven structures with stoichiometry BC₂N and varied atomic arrangements. We calculated the formation energy for each arrangement, and determined that it is low (high) when the number of boron-carbon and nitrogen-carbon bonds is low (high). We found that the formation energy of many our structures compared favorably with a previous literature proposal. Regarding the electronic properties, we found that the investigated structures are semiconducting, with band gaps ranging from 0.02 to 2.00 eV. Moreover, we determined that most of the B_xC_yN_z hybrid α-graphynes proposed here strongly absorb infrared light, and so could potentially find applications in optoelectronic devices such as heat sensors and infrared filters.

Hybrid graphynes composed of boron, carbon, and nitrogen are investigated using DFT calculations. The proposed materials are semiconductors and strongly absorb infrared light.