Properties of interfaces between metal–organic frameworks and ionic liquids

<sec><p indent="0mm">Propylene is an important part of the petrochemical industry, and its global market size has exceeded $120 billion. However, the existing propylene production process is frequently observed with the presence of propane. The separation process of propylene and propane is one of the most energy consuming processes in industrial development because of the similar structure and physical and chemical properties between them. Traditional cryogenic rectification techniques are beset with limitations such as inadequate separation efficiency and high energy consumption. Given the carbon peaking and carbon neutrality goals, it is imperative to develop environmentally friendly separation materials for propylene/propane that not only conserve energy but also enhance separation efficiency. Ionic liquids (ILs), with their characteristics of adjustable physical and chemical properties of structure, lower volatility than other organic solvents and rich hydrogen bond network, have wide significant interest in gas separation applications. ILs exhibit a unique absorption ability, which can selectively separate between propylene and propane through strong hydrogen bonding interactions or via π complexation with transition metal salts. ILs have been recognized as a new generation of efficient separation materials for propylene/propane separation, offering significant advantages in propylene absorption capacity, selectivity and cycle stability, and more. </sec><sec> In this work, the current research on propylene/ propane separation processes by using ionic liquids was firstly summarized, focusing on the optimal design of ILs, composite methods involving transition metal salts, and the underlying adsorption mechanisms. Subsequently, the influences of the structure of ILs (including the groups on the cation and anion of ILs, the length of side chain alkyl chain of cation, and the combination with transition metal salts), the properties of ILs (viscosity and cycle stability) and absorption conditions (temperature, pressure, concentration of transition metal salts) on the separation performance were discussed in detail. The results showed that the use of unsaturated groups on cations and anions or the reduction of side chain length both strengthen selective absorption capacity for propylene. Simultaneously, better gas separation performance can be achieved by reducing viscosity, increasing absorption pressure and increasing transition metal content. </sec><sec> Secondly, this article also outlines two methods for researchers to explore ILs-based functional materials for the purpose of making full use of the gas separation performance of ionic liquids and overcoming the influence of viscosity on gas diffusion. The initial strategy is to be combined ILs with porous adsorbents (such as metal-organic frameworks (MOFs)) to enhance their dispersion. For the second approach, ILs is utilized as raw material for membrane preparation to achieve propylene/propane separation. These studies about membrane preparation by using ILs not only investigated the separation properties of different ionic liquid composites, but also revealed the potential mechanism of their application in gas separation processes. </sec><sec> Finally, propylene/propane separation and the feasibility study of industrial applications were reviewed, such as the design and synthesis of ILs, the design and preparation of ILs membrane materials, the development of MOFs material combination, the application research of screening simulation and machine learning technology and so on. Hoping to provide useful reference for propylene/propane separation by using ILs. This work illustrates that the application of ILs shows great potential in the field of propylene/propane separation. The feature research direction of propylene/propane separation materials was proposed. In our opinion, many new ILs materials will be made great breakthrough in propylene/propane separation and industrial application in the future. </sec>

Metal organic frameworks (MOFs) are a class of porous polymeric material composed of metal ions or clusters linked together by organic bridging ligands. Their large surface areas accompanied by uniform pores, open metal sites, and diverse available post-synthesis functionalization routes make MOFs promising candidate materials for gas storage, separation, and heterogeneous catalysis. MOFs are typically synthesized by solvothermal reactions in organic solvents or in water, but have also been prepared in ionic liquids (ILs) recently; examples of the latter include Cu-BTC (BTC: 1,3,5-benzenetricarboxylate), Ln-BTC, Cd-BTC, Zn-BTC, and others. ILs have been attracting increasing attention as a solvent of choice for chemical synthesis, because of their unique integration of various properties such as essentially zero vapor pressure, excellent solvating properties, easy recyclability, and high thermal stability. The majority of the reports dealing with MOF synthesis have focused on ILs derived from 1-alkyl-3-methylimidazolium. However, deep eutectic solvents (DESs), mixtures of two or more compounds that have melting points lower than that of either of their constituents, are known to exhibit solvent properties very similar to those of ILs and have been employed for MOF synthesis. They have advantages over other types of ILs such as ease of preparation as pure phases from easily available components, low prices, and relative unreactivity towards atmospheric moisture. DES can act as both a solvent and a ligand during the MOF synthesis. MOFs can be synthesized by sonochemical method which has exhibited rapid synthesis kinetics, uniform particle morphology, and excellent phase purity in inorganic materials synthesis. The sonochemical method promotes homogeneous nucleation and reduces crystallization time considerably via the creation, growth, and collapse of an acoustic cavity, generating extremely high temperature (5000-25000 K)/pressure as well as fast heating and cooling rates. In the sonochemical synthesis route, in connection with this reaction mechanism, DESs are thought to create cavitation easily at relatively high temperatures due to their low vapor pressures, and thus have good potential as a reaction medium in the sonochemical synthesis of nanomaterials. In this work, we have chosen the widely investigated Cu3(BTC)2 as a representative MOF material for sonochemical synthesis using choline chloride/dimethylurea DES as a solvent (designated as S-CuBTC). To the best of our knowledge, this is the first report of sonochemical synthesis of a MOF structure in a DES. Effects of various synthesis parameters on the crystallization process of Cu3(BTC)2 were examined, and the properties of the sample were compared to those of Cu3(BTC)2 prepared via a conventional ionothermal synthesis route in an oven (designated as C-CuBTC). In order to use MOFs for adsorption, rigorous guest removal from the pores has to be performed so as to achieve the highest possible surface area (and pore volume). This is typically accomplished by solvent washing and vacuum treatment. Since the mixture of choline chloride and 1,3dimethylurea in a molar ratio of 1:2 used in this work has a eutectic temperature of around 70 C, removal of the solvent guest before it solidifies inside the pores is challenging. Thus, an effective activation procedure for Cu3(BTC)2 samples obtained under ionothermal synthesis conditions was briefly examined by conducting repeated sample washing with de-ionized water and ethanol in the manner described in entries I to V in Table 1. No apparent PXRD patterns or morphology changes were observed after washing step II (see Figure S1 and S2). The corresponding SEM images after different washing steps did not reveal any noticeable differences either, except that the DES coated at the external surface in the Cu3(BTC)2 sample was removed. However, repeated washing (200 mL × 2) by de-ionized water and ethanol was necessary to obtain the BET surface area of a high quality Cu3(BTC)2, as shown in Table 1. Elemental analysis of the C-CuBTC sample after washing treatment IV confirmed the virtual elimination of DES; The

The present study focused on CO2 capture, storage, and conversion through the innovative integration of plasma–ionic liquid (IL) technology. For the first time, we employed plasma-IL technology to confront climate change challenges. We utilized 1-Butyl-3-methylimidazolium chloride IL to capture and store CO2 under atmospheric pressure, and subsequently employed plasma to induce the transformation of IL-captured CO2 into CO. Furthermore, we performed computer simulations to enhance our understanding of the CO2 and CO capture processes of water and IL solutions. This comprehensive approach provides valuable insights into the potential of plasma–IL technology as a viable solution for climate change.

금속유기구조체(metal-organic frameworks, MOF)는 넓은 비표면적, 규칙적인 구조 및 높게 분산된 금속 성분 등 뛰어난 물리화학적 특성으로 인해 활발한 연구가 이뤄지고 있는 다공성 물질이며, 특히 가스의 흡착, 분리 매체로서 뛰어난 성능이 보고되고 있다. MOF를 이용한 온실가스 이산화탄소의 흡착 연구는 상온 고압 영역에서 이산화탄소 저장 공정과 상온 저압 영역에서 이산화탄소 흡착 공정의 두 범주로 나눌 수 있으며, MOF의 넓은 비표면적 외에도 (1) MOF의 빈 배위결합 자리, (2) MOF의 기능화, (3) MOF의 상호 침투 효과, 및 (4) 이온 교환 효과를 이용한 연구 결과가 보고되고 있다. MOF 물질들은 비교적 낮은 수분 및 열에 대한 안정성이 문제로 제기되고 있으며, 제올라이트 유사 구조체(zeolitic imidazolate frameworks, ZIF) 또는 유기 골격 구조체(covalent organic frameworks, COF) 물질의 이산화탄소 흡착 특성이 거론되고 있다. 본 소고에서는 MOF를 이용한 이산화탄소 흡착에 대한 최근의 연구 결과를 본 연구실의 실험 결과를 중심으로 간략히 소개하고자 한다. Metal organic frameworks (MOFs) are a class of crystalline organic-inorganic hybrid compounds formed by coordination of metal clusters or ions with organic linkers. MOFs have recently attracted intense research interest due to their permanent porous structures, large surface areas and pore volume, high-dispersed metal species, and potential applications in gas adsorption, separation, and catalysis. <TEX>$CO_2$</TEX> adsorption in MOFs has been investigated in two areas of <TEX>$CO_2$</TEX> storage at high pressures and <TEX>$CO_2$</TEX> adsorption at atmospheric pressure conditions. In this short review, <TEX>$CO_2$</TEX> adsorption/separation results using MOFs conducted in our laboratory was explained in terms of four contributing effects; (1) coordinatively unsaturated open metal sites, (2) functionalization, (3) interpenetration/catenation, and (4) ion-exchange. Zeolitic imidazolate frameworks (ZIFs) and covalent organic frameworks (COFs) were also considered as a candidate material.

Insights into zeolite imidazole frameworks (ZIFs) for CO2 capture and separation: A short review.

Industrial separation processes comprise approximately 10% of the global energy demand, driven largely by the utilization of thermal separation methods (e.g., distillation). Significant energy and cost savings can be realized using advanced separation techniques such as membranes and sorbents. One of the major barriers to acceptance of these techniques remains creating materials that are efficient and productive in the presence of aggressive industrial feeds. One promising class of emerging materials is zeolitic imidazolate frameworks (ZIFs), an important thermally and chemically stable subclass of metal organic frameworks (MOFs). The objectives of this paper are (i) to provide a current understanding of the synthetic methods that enable the immense tunability of ZIFs, (ii) to identify areas of success and areas for improvement when ZIFs are used as adsorbents, (iii) to identify areas of success and areas for improvement in ZIF membranes. A review is given of the state-of-the-art in ZIF synthesis procedures and novel ZIF formation pathways as well as their application in energy efficient separations.

A type-III porous liquid based on zeolitic imidazolate framework-8 (ZIF-8) and an ionic liquid trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl)imide ([THTDP][BTI]) was synthesized and used for the desulfurization of model diesel. The desulfurization effect by ZIF-8/[THTDP][BTI] combined both the adsorptive desulfurization by ZIF-8 and the extraction desulfurization by [THTDP][BTI]. The removal of the three chosen aromatic organic sulfides by the ZIF-8/[THTDP][BTI] porous liquid followed the order of dibenzothiophene (73.1%) > benzothiophene (70.0%) > thiophene (61.5%). It was further found that deep desulfurization could be realized by ZIF-8/[THTDP][BTI] through triple desulfurization cycles and ZIF-8/[THTDP][BTI] can be regenerated readily. The desulfurization mechanism was explored further in detail by conformation search and density functional theory calculations. Calculations supported that the large molecular volume of [THTDP][BTI] excluded itself from the cavities of ZIF-8, making the pores of ZIF-8 in the porous liquid unoccupied and accessible by other guest species, here the studied organic sulfides. These calculations indicate that the van der Waals interactions were the main interactions between ZIF-8/[THTDP][BTI] and specifically benzothiophene. This work supports that the porous liquid ZIF-8/[THTDP][BTI] could potentially be used for desulfurization of diesel in industry.

A comparison of the CO2 capture characteristics of zeolites and metal–organic frameworks

Removal and sequestration of CO2 from flue gas has been proposed as one of the most reliable solutions to mitigate globe greenhouse emissions. Adsorption technology based on porous adsorbent is known to be one of the most efficient processes for the CO2 capture from flue gas. The key issue of this technology is to find the adsorbent with high adsorption capacity and selectivity for CO2. In this chapter, both the experimental and the computer simulation works about the CO2 adsorption behavior on porous materials in our laboratory were introduced. In the experimental works, the mesoporous materials such as MCM-41 and SBA-15 were selected as the fundamental adsorbent. After surface modification by aminosilane, the amine groups became active centers and the CO2 adsorption capacity was obviously increased due to the chemisorption. It is shown that the dual amine groups of AEAPMDS had better effect on CO2 adsorption than the single amine group of APTS. The best CO2 adsorption capacity of MCM-41-AEAPMDS was 2.20 mmol·g-1 at room temperature. Another effective way was incorporation metal Mg into the mesoporous materials. By various impregnating or doping methods, such as the co-condensation, the dispersion with the enhancement of Al3+ or amine, and the ionic exchange, a suitable amount of Mg2+ can be successfully introduced into MCM-41 and SBA-15, which effectively increased the CO2 adsorption capacity. Different pore structures had their corresponding optimized methods, the real reason behind was the highly dispersed MgO state in the channels. The best CO2 adsorption capacities of Mg-Al-SBA-15-D1 and Mg-EDA-MCM-41-D10 were about 1.35 mmol·g-1. In the simulation works, some novel porous materials such as the micro/mesoporous composite, the covalent organic frameworks, the metal organic framework and the zeolitic imidazolate frameworks were selected as the potential adsorbents for the CO2 capture. The CO2 adsorption behavior of the zeoilte of MFI, the mesoporous MCM-41 and the micro/mesoporous composite of MFI/MCM-41 were simulated and compared. It is revealed that the micro/mesoporous composite had better performances on the CO2 adsorption capacity and selectivity at high pressure, as well as the diffusion performance.

Removal of low Sb(V) concentrations from mining wastewater using zeolitic imidazolate framework-8

Improvement of solubility of sparingly water-soluble drug triggered by metal-organic framework

Synthesis of nanoscale zeolitic imidazolate framework-8 (ZIF-8) using reverse micro-emulsion for Congo red adsorption

Recent prospects and trends on zeolitic imidazolate frameworks for microwave absorption and EMI shielding applications

Rising CO2 levels, largely from flue gas emissions, are a significant contributor to global climate change. Adsorption using Metal-Organic Frameworks (MOFs) offers a promising solution for CO2 capture due to their high surface area, tunable porosity, and selectivity. To streamline the discovery of efficient MOFs, we developed a high-throughput virtual screening (HTVS) pipeline by integrating Grand-Canonical Monte Carlo (GCMC) simulations, molecular modeling and machine learning. We screened a filtered subset of the CoREMOF database and a user-defined hypothetical MOF bank to identify candidates with high CO2 adsorption capacity and selectivity. This approach yielded several high-performing MOFs, including five from the CoREMOF dataset and a new structure from the hypothetical bank exceeding the performance of existing MOFs. Our findings highlight the complex relationship between MOF geometries and CO2 capture performance, emphasizing the importance of features like open metal sites and pore geometry. This computational framework accelerates MOF discovery and provides valuable insights for experimental synthesis. Future work will focus on expanding the hypothetical MOF dataset, improving simulation accuracy, and employing advanced optimization techniques to enhance the screening process.

Selective CO2 capture in industrial streams is of paramount importance to decrease actual emissions to the atmosphere, and to minimize the associated environmental concerns. Among the different possibilities to capture CO2, adsorption using nanoporous networks is one of the most promising approaches, provided that the adsorbent can be properly designed in terms of porous structure and surface chemistry. The material has to be designed to achieve a preferential interaction with CO2 versus other competing molecules (e.g., CH4, N2, O2, etc.) also present in the industrial effluents. Promising adsorbents for CO2 capture include activated carbons, zeolites, and metal–organic frameworks (MOFs), among others. This chapter will focus on activated carbon materials and the effect of the porous structure and surface chemistry in the selective adsorption of CO2. Although the chapter will concentrate mainly in physisorption processes, a final section will be introduced devoted to a novel approach for CO2 capture based on natural processes, the so-called solid state storage.