Metal-Free Modified Boron Nitride for Enhanced CO2 Capture

Porous boron nitride is a new class of solid adsorbent with applications in CO2 capture. In order to further enhance the adsorption capacities of materials, new strategies such as porosity tuning, element doping and surface modification have been taken into account. In this work, metal-free modification of porous boron nitride (BN) has been prepared by a structure directing agent via simple heat treatment under N2 flow. We have demonstrated that textural properties of BN play a pivotal role in CO2 adsorption behavior. Therefore, addition of a triblock copolymer surfactant (P123) has been adopted to improve the pore ordering and textural properties of porous BN and its influence on the morphological and structural properties of pristine BN has been characterized. The obtained BN-P123 exhibits a high surface area of 476 m2/g, a large pore volume of 0.83 cm3/g with an abundance of micropores. More importantly, after modification with P123 copolymer, the capacity of pure CO2 on porous BN has improved by about 34.5% compared to pristine BN (2.69 mmol/g for BN-P123 vs. 2.00 mmol/g for pristine BN under ambient condition). The unique characteristics of boron nitride opens up new routes for designing porous BN, which could be employed for optimizing CO2 adsorption

Carbon–GO Composites with Preferential Water versus Ethanol Uptake

The elimination of small amounts of water from alcohols is by no means a trivial issue in many practical applications like, for instance, the dehumidification of biocombustibles. The use of carbonaceous materials as sorbents has been far less explored than that of other materials because their hydrophobic character has typically limited their water uptake. Herein, we designed a synthetic process based on the use of eutectic mixtures that allowed the homogeneous dispersion of graphene oxide (GO) in the liquid containing the carbon precursor, e.g., furfuryl alcohol. Thus, after polymerization and a subsequent carbonization process, we were able to obtain porous carbon–GO composites where the combination of pore diameter and surface hydrophilicity provided a remarkable capacity for water uptake but extremely low methanol and ethanol uptake along the entire range of relative pressures evaluated in this work. Both the neat water uptake and the uptake difference between water and either methanol or ethanol of our carbon–GO composites were similar or eventually better than the uptake previously reported for other materials, also exhibiting preferential water-to-alcohol adsorption, e.g., porous coordination polymers, metal–organic frameworks, polyoxometalates, and covalent two-dimensional nanosheets embedded in a polymer matrix. Moreover, water versus alcohol uptake was particularly remarkable at low partial pressures in our carbon–GO composites.This work was supported by MINECO/FEDER (Project Numbers MAT2015-68639-R, MAT2016-80285-P, and RTI2018-097728-B-I00). L.Z.G. acknowledges the Chinese Scholarship Council for a PhD research fellowship (CSC No. 201608330266). C.C.-C. acknowledges UA for a research contract

Synthesis and modification of porous boron nitride materials for application in carbon dioxide capture

Global warming, which is often confused with “climate change”, can cause longlasting, irreversible, catastrophic and far-reaching effects on the earth and the lives of the future generations. There is a unanimous agreement that global warming is mainly due to human activities and above all, burning fossil fuels for industrial applications and emission of CO2 as one of the major contributors of global warming. To mitigate the amount of CO2 emission and to offset its effect, the governments around the world have united to take necessary actions in an effective and efficient way by a variety of policy changes and adoption of technologies such as carbon capture and storage. For instance, the UK government has set out measures to tackle climate change with a plan for the UK to be a pioneering economy in the world towards a zero-emission economy by 2050. Among the technologies used for carbon capture, those derived from solid sorbents for CO2 capture attract growing interest in industrial applications. The popularity of using these technologies is attributed to their lower energy penalty, high selectivity, recyclability and ease of manufacturing. Developments of new materials with low cost is fundamental, even though numerous solid sorbents have been examined for CO2 capture to date. Porous boron nitride (BN) has been recognised as a promising alternative to be used in carbon adsorption process due to its unique advantages including its bond polarity, tuneability and high thermal and chemical stabilities. So far, a systematic understanding of how its distinctive properties (pore structure and chemistry) contributes to capture carbon dioxide is still lacking. To develop a favourable porous BN, further work is required to establish the viability of these materials as cost-effective adsorbents. This research presents synthesis and modification strategies of porous BN and a characterisation of the material for carbon capture application. Various synthesis conditions have been developed to obtain high surface area (>700 m2/g) pristine BN material via template free method. The study pursued two distinct strategies to modify pristine porous BN, aiming to enhance its CO2 adsorption performance. Firstly, a focus on controlling the pure BN porosity has been implemented by tuning with a polymeric surfactant as non-metal modification approach. The capacity of pure CO2 on nonmetal modified porous BN has been enhanced by about 34.5% compared to pristine BN in ambient conditions. The study highlights the significant role of porosity/pore size of BN for CO2 adsorption. Secondly, a novel approach has been implemented for modifying pore structure and surface chemistry of pristine BN by introduction of Ni (II) into BN framework. The pure CO2 capture experiment has been assessed, considering three different temperatures and the results confirmed that the basic sites on porous BN contribute to its ability to adsorb more CO2 relative to pure BN. The method has been validated as a feasible route to improve porous BN performance in CO2 adsorption process even at realistic flue gas temperatures (above 298 K). Finally, the stability and reusability of pristine BN samples with various porosity and chemistry have been examined over the eight adsorption-desorption cycles. Overall, this dissertation demonstrated that porous BN materials possess a combination of desirable properties with flexibility for functionalisation and lower regeneration energy. Thus, it can be considered as an effective adsorbent for future large-scale carbon capture technologies

Hydrogen-bond supramolecular hydrogels as efficient precursors in the preparation of freestanding 3D carbonaceous architectures containing BCNO nanocrystals and exhibiting a high CO2/CH4 adsorption ratio

Oxygen-enriched boron carbonitrides – known as boron carbon oxinitrides, BCNOs – have exhibited remarkable properties with numerous works reporting on their performance as phosphors and some few ones as H2-adsorbents. However, the study of BCNOs capability for CO2 uptaking has yet to be achieved. Herein, we have designed a simple process for preparation of freestanding three-dimensional (3D) BCNO structures via pyrolysis of supramolecular gels formed by H-bonding of melamine, boric acid and glucose. The 3D porous materials obtained by pyrolysis of supramolecular gels containing glucose exhibited a seaweed-like 3D structure formed by BCNO nanocrystals embedded within a carbonaceous matrix with a certain content of amorphous hydrogenated carbon. The particularly narrow porosities exhibited by these samples proved effective for CO2 adsorption with uptakes of up to ca. 1.8 mmol/g at 25 °C. More interestingly, those samples prepared with high concentration of glucose behaved as molecular sieves and exhibited an excellent performance for CO2–CH4 separation, especially at low pressures with kH values of up to 1.04∙103.This work was supported by MINECO/FEDER (Project Numbers MAT2015-68639-R and MAT2016-80285-P). N. López-Salas also acknowledges MINECO/FEDER for a FPI research contract. C. Cuadrado-Collados and J. Gandara-Loe acknowledge UA and GV (GRISOLIAP/2016/089) for their respective research contracts