Structuring ZIF-8-based hybrid material with hierarchical pores by in situ synthesis and thermal treatment for enhancement of CO2 uptake

Recent Advances of Carbon Capture in Metal-Organic Frameworks: A Comprehensive Review

The excessive emission of greenhouse gases, which leads to global warming and alarms the world, has triggered a global campaign for carbon neutrality. Carbon capture and sequestration (CCS) technology has aroused wide research interest as a versatile emission mitigation technology. Metal-organic frameworks (MOFs), as a new class of high-performance adsorbents, hold great potential for CO2 capture from large point sources and ambient air due to their ultra-high specific surface area as well as pore structure. In recent years, MOFs have made great progress in the field of CO2 capture and separation, and have published a number of important results, which have greatly promoted the development of MOF materials for practical carbon capture applications. This review summarizes the most recent advanced research on MOF materials for carbon capture in various application scenarios over the past six years. The strategies for enhancing CO2 selective adsorption and separation of MOFs are described in detail, along with the development of MOF-based composites. Moreover, this review also systematically summarizes the highly concerned issues of MOF materials in practical applications of carbon capture. Finally, future research on CO2 capture by MOF materials is prospected.

Efficient CO2 adsorption using chitosan, graphene oxide, and zinc oxide composite

This study was deeply focused on developing a novel CTS/GO/ZnO composite as an efficient adsorbent for CO2 adsorption process. To do so, design of experiment (DOE) was done based on RSM-BBD technique and according to the DOE runs, various CTS/GO/ZnO samples were synthesized with different GO loading (in the range of 0 wt% to 20 wt%) and different ZnO nanoparticle's loading (in the range of 0 wt% to 20 wt%). A volumetric adsorption setup was used to investigate the effect of temperature (in the range of 25-65 °C) and pressure (in the range of 1-9 bar) on the obtained samples CO2 uptake capability. A quadratic model was developed based on the RSM-BBD method to predict the CO2 adsorption capacity of the composite sample within design space. In addition, CO2 adsorption process optimization was conducted and the optimum values of the GO, ZnO, temperature, and pressure were obtained around 23.8 wt%, 18.2 wt%, 30.1 °C, and 8.6 bar, respectively, with the highest CO2 uptake capacity of 470.43 mg/g. Moreover, isotherm and kinetic modeling of the CO2 uptake process were conducted and the Freundlich model (R2 = 0.99) and fractional order model (R2 = 0.99) were obtained as the most appropriate isotherm and kinetic models, respectively. Also, thermodynamic analysis of the adsorption was done and the ∆H°, ∆S°, and ∆G° values were obtained around - 19.121 kJ/mol, - 0.032 kJ/mol K, and - 9.608 kJ/mol, respectively, indicating exothermic, spontaneously, and physically adsorption of the CO2 molecules on the CTS/GO/ZnO composite's surface. Finally, a renewability study was conducted and a minor loss in the CO2 adsorption efficiency of about 4.35% was obtained after ten cycles, demonstrating the resulting adsorbent has good performance and robustness for industrial CO2 capture purposes.

Enhanced Gas Adsorption in HKUST-1@Chitosan Aerogels, Cryogels, and Xerogels: An Evaluation Study

This study investigates the use of chitosan hydrogel microspheres as a template for growing an extended network of MOF-type HKUST-1. Different drying methods (supercritical CO2, freeze-drying, and vacuum drying) were used to generate three-dimensional polysaccharide nanofibrils embedding MOF nanoclusters. The resulting HKUST-1@Chitosan beads exhibit uniform and stable loadings of HKUST-1 and were used for the adsorption of CO2, CH4, Xe, and Kr. The maximum adsorption capacity of CO2 was found to be 1.98 mmol·g-1 at 298 K and 1 bar, which is significantly higher than those of most MOF-based composite materials. Based on Henry's constants, thus-prepared HKUST-1@CS beads also exhibit fair selectivity for CO2 over CH4 and Xe over Kr, making them promising candidates for capture and separation applications.

Continuous Synthesis of Nanodroplet-Templated, N-Doped Microporous Carbon Spheres in Microfluidic System for CO2 Capture

Microporous carbon has been widely known as a probable material to capture greenhouse gases. This work provides a facile synthesis of monodisperse biomass-derived microporous carbon spheres (CSs) for effective CO₂ capture. The spheres were synthesized by a novel continuous microfluidic strategy from oil-in-water-in-oil ((O₁/W₂)/O₂) emulsions. O₁ nanodroplets could be self-assembled into the cores of micelles, which were formed by chitosan and surfactant F127 in the W₂ phase through high-speed liquid-phase shearing. The obtained O₁/W₂ emulsion can be further sheared into a sphere by the O₂ phase. After carbonization, nanodroplet-templated pores shrank to micropores and ultramicropores. The optimal sample showed the developed pore structure with a Brunauer-Emmett-Teller (BET) surface area of 576 m²/g and microporous volume of 0.22 cm³/g. Compared with O₁ free CS, the dynamic adsorption capacity of CO₂ was improved to 1.20 mmol/g from 0.42 mmol/g. The CO₂ capture capacity, cycling stability, isosteric heats, and mass diffusion coefficient of CSs were evaluated as well. The results demonstrate that microporous CSs are promising candidates for CO₂ capture with low cost and a green synthesis route, which was achieved via continuous microfluidic strategy using sustainable biomass chitosan as a carbon precursor and droplets as templates.

Nano-gate opening pressures for the adsorption of isobutane, n-butane, propane, and propylene gases on bimetallic Co–Zn based zeolitic imidazolate frameworks

In this article, zeolitic-imidazolate framework-8 (ZIF-8) and its mixed metal CoZn-ZIF-8 were synthesized via a rapid microwave method. They exhibited a nanogate opening pressure threshold for the adsorption of C₃ and C₄ compounds.

Chitosan grafted graphene oxide aerogel: Synthesis, characterization and carbon dioxide capture study

We have demonstrated a superficial, environmentally friendly and sustainable development of chitosan (CS) grafted graphene oxide aerogels for adsorption of CO₂ gas. The CS is grafted into the carbonaceous materials like graphene oxide, multi-walled carbon nanotubes etc. to provide the large surface area, high porosity and a large number of amine group which facilitates the adsorption of CO₂ gas. CS and carbonaceous materials undergo crosslinking by using cross-linker reagents, and freeze-drying technique to yield CS based aerogels with ordered porous structures. Crosslinking between CS and carbonaceous materials was confirmed by FT-IR. Physical properties of the CS-based aerogels were studied using SEM, TGA, XRD, BET isotherm analysis. The adsorption capacity of CO₂ gas by CS grafted graphene oxide aerogels is around 0.257 mmol g^-1 at 1 bar, that is significantly higher in comparison to the adsorption capacity of pure CS. We believe that this study helps to reduce the cost of adsorbents due to the large availability of marine waste (CS) and thus aims to reduce the anthropogenic CO₂ gas at low cost, favourable temperature and pressure as compared to previously reported.