Self-assembling imidazolium-based ionic liquid in rigid nanopores induces anomalous CO2 adsorption at low pressure

An alkylimidazolium-based long-chain ionic liquid (LCIL) was immobilized in silica nanopores via a supramolecular assembly approach. To discuss the characteristic features of LCIL in a confined nanospace, except for the characteristics of the host materials, we have prepared the silica host with monodisperse morphology and a nanostructured system to immobilize LCIL. The nanostructure is composed of three distinct regions: the silica framework, the hydrophobic interior of the alkyl chains, and the organic-inorganic ionic interface. Anomalous CO(2) adsorption sites were found to be well-ordered locations on the ionic interface fabricated by the π-π-stacked imidazolium heads containing inorganic anions and polar silica surfaces.     

Amino functionalised Silica-Aerogels for CO2-adsorption at low partial pressure

Effective adsorption of CO₂ at low partial pressures is required for many technical processes, such as gas purification or CO₂ removal in closed loop environmental control systems. Since the concentration of CO₂ in such applications is rather low, a high adsorption capacity is a required property for the adsorbent. Silica aerogels possessing an open pore structure, a high porosity and a high surface area, have a great potential for utilisation as CO₂ adsorbents. Nonetheless in order to reach high adsorption capacities, silica aerogels should be functionalised, for instance by amino functionalisation. In this work, two different functionalisation methods were applied for the generation of amino functionalised aerogels: co-condensation during the sol-gel process and post-treatment of the gel. The co-condensation functionalisation allows the introduction of up to 1.44 wt.% nitrogen into the aerogel structure with minor reductions in surface area, leading however only to minor increases in the adsorption capacity at low partial pressures. The post functionalisation of the gel causes a greater loss in surface area, but the CO₂ adsorption capacity increases, due to the introduction of higher amounts of amino groups into the aerogel structure (up to 5.2 wt.% nitrogen). Respectively, 0.523 mmol CO₂/g aerogel could be adsorbed at 250 Pa. This value is comparable with the adsorption capacity at this pressure of a standard commercially available adsorbent, Zeolite 13X.     

Selective CO2 adsorption in a robust and water-stable porous coordination polymer with new network topology

A robust and water-stable porous coordination polymer [Cd(NDC)(0.5)(PCA)]·G(x) (1) (H(2)NDC = 2,6-napthalenedicarboxylic acid, HPCA = 4-pyridinecarboxylic acid, G = guest molecules) with new network topology has been synthesized solvothermally. The framework is 3D porous material and forms a 1D channel along the c-axis, with the channel dimensions ~9.48 × 7.83 ?(2). The compound has high selectivity in uptake of CO(2) over other gases (H(2), O(2), Ar, N(2), and CH(4)). The framework is highly stable in presence of water vapor even at 60 °C. The high CO(2) selectivity over other gases and water stability makes the compound promising candidate for industrial postcombustion gas separation application.     

SAXS study of polymer adsorption on porous ZrO2

The small‐angle X‐ray scattering method (SAXS) has been used for the analysis of polymer adsorption on porous ZrO₂. Particular attention has been paid to the adsorption of polyacrylic acid (PAA) and polyacrylamide (PAM) on the surface of porous ZrO₂. It has been established that the SAXS method determines whether the polymer has penetrated the carrier's pores, and that polymers of low molecular weight create a thin transition layer on the surface of ZrO₂ (understood in the context of a change in the electron density). The creation of this layer is clearly reflected in the run of SAXS curves (Porod's plot). Ruland–Vonk's method has been used to determine the thickness of the transition layer. The results are consistent with those obtained when the viscosity method was used. Copyright © 2003 John Wiley & Sons, Ltd.     

多孔材料的二氧化碳吸附与光催化转化研究进展(英文)

太阳能光催化是CO_2转化和利用的新兴技术,直接利用洁净充足的太阳能将自然界富有的"温室气体"CO_2转化成化学燃料,不仅有利于消除大气温室效应,而且能缓解能源短缺问题,因而成为人们研究的一个重要方向.但目前CO_2的吸附和转换效率还很低,这是太阳能光催化CO_2资源化的最大障碍.高性能光催化剂的设计和合成是这项技术的关键.针对CO_2光还原反应的特异性,理想的光催化材料应该具有以下功能:强的CO_2吸附能力和高的光催化活性.将光催化剂与对CO_2具有高吸附性的多孔材料结合,就可以将CO_2吸附并富集在吸附剂周围的光催化剂表面上以进行催化转化,因此基于高效多孔吸附材料构筑光催化体系成为光催化转化CO_2的重要研究方向之一.CO_2的循环利用包括吸附和转化两方面,高吸附量的多孔材料是获得CO_2高转化效率的前提.本文首先以多孔材料结构参数及性能指标为主线,对无机多孔材料、金属有机框架材料及微孔有机聚合物材料的研究进展及应用前景进行了评述.通过对多孔材料的改性和新型多孔材料的开发,CO_2的吸附能力得到一定的提升,但是仅仅依靠多孔材料的吸附分离,不能实现CO_2中的碳资源循环.在此基础上,本文重点评述了多孔光催化材料在CO_2光催化转化中的最新研究进展.采用多孔材料与光催化剂结合,可增加材料的比表面积,在界面处暴露更多的活性位点,有利于光催化CO_2转化的进行;同时,通过孔结构和基团调控,可以调控光催化剂的反应活性和产物选择性.特别是金属有机框架材料与微孔有机聚合物材料,改变构建单元的官能团和制备技术还可以实现光谱响应范围的调控,提高太阳光的利用率.大量文献对比发现,引入较高CO_2吸附效率的多孔材料构建光催化体系,CO_2光催化转化的效率及产物选择性显著提高.最后,本文对多孔材料在CO_2光催化转化领域的研究现状与亟待解决的问题进行了剖析,提出了下一步可能的研究方向:(1)提高多孔材料自身的稳定性如耐水性能与光/热稳定性;(2)发展光催化材料在多孔载体的微观组装方法,不影响CO_2吸附效率的前提下提高光催化活性;(3)深入研究多孔光催化材料内部与表面的CO_2转化机理,为进一步提高吸附与转化效率提供理论指导.     

Silver-anchored porous aromatic framework for efficient conversion of propargylic alcohols with CO2 at ambient pressure

The conversion of propargylic alcohols and carbon dioxide (CO₂) into fine chemicals suffers from issues of harsh reaction conditions and difficult catalyst recovery. To achieve efficient CO₂ activation at low energy consumption, a silver-anchored porous aromatic framework catalyst Ag@PAF-DAB with high active phase density and CO₂ adsorption capacity was proposed. Since Ag@PAF-DAB has the dual functions of CO₂ capture and conversion, propargylic alcohols were completely converted into α-alkylidene cyclic carbonate or α?hydroxy ketone as high value-added product under atmospheric pressure (CO₂, 0.1 MPa) and low silver equivalent (0.5 mol%). Notably, Ag@PAF-DAB exhibited broad substrate diversity, high stability, and excellent reusability. By applying FTIR and GC, the key to green synthetic route of α?hydroxy ketone was confirmed to lie in the further hydration of α-alkylidene cyclic carbonate.     

Understanding the preferential adsorption of CO2 over N2 in a flexible metal-organic framework

The unusual uptake behavior and preferential adsorption of CO(2) over N(2) are investigated in a flexible metal-organic framework system, Zn(2)(bdc)(2)(bpee), where bpdc = 4,4'-biphenyl dicarboxylate and bpee = 1,2-bis(4-pyridyl)ethylene, using Raman and IR spectroscopy. The results indicate that the interaction of CO(2) with the framework induces a twisting of one of its ligands, which is possible because of the type of connectivity of the carboxylate end group of the ligand to the metal center and the specific interaction of CO(2) with the framework. The flexibility of the bpee pillars allows the structure to respond to the twisting, fostering the adsorption of more CO(2). DFT calculations support the qualitative picture derived from the experimental analysis. The adsorption sites at higher loading have been identified using a modified van der Waals-Density Functional Theory method, showing that the more energetically favorable positions for the CO(2) molecules are closer to the C═C bond of the bpee and the C-C bond of the bpdc ligands instead of the benzene and pyridine rings of these ligands. These findings are consistent with changes observed using Raman spectroscopy, which is useful for detecting both specific guest-host interactions and structural changes in the framework.     

Mn(II)-based porous metal-organic framework showing metamagnetic properties and high hydrogen adsorption at low pressure

A Mn(II)-based homometallic porous metal-organic framework, Mn(5)(btac)(4)(μ(3)-OH)(2)(EtOH)(2)·DMF·3EtOH·3H(2)O (1, btac = benzotriazole-5-carboxylate), has been solvothermally synthesized and structurally characterized by elemental analysis, thermogravimetric analysis, and X-ray crystallographic study. 1 is a 3D neutral framework featuring 1D porous channels constructed by {Mn-OH-Mn}(n) chains and btac linkers. Magnetic studies show that 1 is a 3D metamagnet containing 1D {Mn-OH-Mn}(n) ferrimagnetic chains. High-pressure H(2) adsorption measurement at 77 K reveals that activated 1 can absorb 0.99 wt % H(2) at 0.5 atm and reaches a maximum of 1.03 wt % at 5.5 atm. The steep H(2) absorption at lower pressure (98.2% of the storage capacity at 0.5 atm) is higher than the corresponding values of some MOFs (MIL-100 (16.1%), MOF-177 (57.1%), and MOF-5 (22.2%)). Furthermore, activated 1 can adsorb CO(2) at room temperature and 275 K. The adsorption enthalpy is 22.0 kJ mol(-1), which reveals the high binding ability for CO(2). Detailed gas sorption implies that the exposed Mn(II) coordination sites in the activated 1 play an important role to improve its adsorption capacities.     

Understanding CO2 adsorption mechanisms in porous adsorbents: A solid-state NMR survey

Reaching a historic high of 36.3 gigatonnes in 2021, global CO₂ emissions from fossil fuel combustion continue to increase at an alarming rate. CO₂ removal technologies are part of the solution to tackle this crucial environmental challenge. Thus, the development of porous materials for storage and capture of gas molecules (in particular, carbon capture and storage) has attracted great interest both in academic and industrial communities due to its potential in mitigating atmospheric CO₂ concentrations.Atomic-scale studies in porous materials are essential to stimulate progress in the design of better CO₂-adsorbents by elucidating gas-sorption surface mechanisms.Spectroscopic techniques have the potential to shed light on the structural details of distinct materials' surfaces, including the type of chemical species formed upon CO₂ adsorption. Herein, we review the last 5 years of scientific developments wherein solid-state NMR and computational studies have been explored to investigate at the atomic level the structure and molecular dynamics of CO₂ species formed at porous surfaces.     

Dynamic porous coordination polymer based on 2D stacked layers exhibiting high sorption selectivity for CO2

A new dynamic porous coordination polymer (PCP) [Ni(dcpy)(bipy)(0.5)(H(2)O)]·1.5H(2)O (1) was synthesized by assembly of 3-(2',5'-dicarboxylphenyl)pyridine (dcpy), 4,4'-bipyridine (bipy) and NiSO(4)via solvothermal, hydrothermal and microwave methods, displaying a wavelike 2D stacked layer framework. Gas adsorption studies for 1 shows a high selective adsorption of CO(2) over other gases (N(2), CH(4) and CO). The adsorption capacity for N(2) can be moderately altered by different activation temperatures demonstrating the framework flexibility of 1.     

Polyaniline-functionalized porous adsorbent for Sr2+ adsorption

To support the nuclear safeguards particle analysis, a method was developed to produce micrometer-sized uranium oxide microspheres with a known uranium content and isotope ratio, which are intended to be characterized as certified reference material. To simplify handling of the produced particles, the collected particles have been transferred into ethanol suspensions. In addition to a demonstration of the suitability and new capabilities of such particle suspensions, such as the preparation of particle mixtures, the stability of the particles has been investigated and demonstrated with regard to dissolution and isotopic exchange.     

Pre-programmed bicomponent porous networks at the solid-liquid interface: the low concentration regime

The control over the formation of a bicomponent porous network was attained by self-assembly at the solid-liquid interface, exploiting triple H-bonds between melamine and bis-uracyl modules.     

三聚氰胺功能化多孔有机聚合物的合成及其对甲基橙的吸附性能

首先以对三联苯(TP)和对苯二甲酰氯(TC)为单体合成了酮基聚合物前体(TP-TC),而后基于席夫碱反应将三聚氰胺(MA)与之交联得到胺功能化的多孔有机聚合物TP-TC-MA。通过扫描电镜(SEM)、透射电镜(TEM)、傅里叶变换红外光谱(FT-IR)、X射线衍射(XRD)、氮气吸附-脱附(BET)以及零电荷点(pH_pzc)的测定等手段对合成的多孔有机聚合物进行表征。以染料废水中典型的阴离子染料甲基橙为研究对象,研究了TP-TC-MA对其吸附行为,并探讨了吸附机制。利用紫外-可见分光光度计(UV-Vis)得出目标污染物的紫外吸收光谱标准曲线,标准曲线拟合相关系数(R²)为0.999。结果表明,TP-TC-MA由于具有高比表面积(708.5 m²/g)和总孔体积(0.556 cm³/g)以及丰富的含氮基团,对阴离子染料甲基橙表现出优异的吸附性能。TP-TC-MA对水中甲基橙的吸附动力学符合准二级动力学方程,吸附平衡数据可以采用Langmuir等温吸附模型描述。经由Langmuir等温吸附模型计算得到的理论最大吸附容量为156.3 mg/g。选择性实验结果表明,TP-TC-MA对阴离子染料甲基橙具有更强的吸附作用,吸附作用机理可归结为静电相互作用、氢键和π-π相互作用等。在重复使用5次之后,TP-TC-MA对甲基橙仍保持90%以上的去除率,表明材料具有良好的稳定性和重复利用性,在染料废水处理中具有很好的应用前景。     

From interpenetrating polymer networks to hierarchical porous carbons for advanced supercapacitor electrodes

A novel and effective strategy to fabricate hierarchical porous carbons for supercapacitors is developed via in-situ activation of interpenetrating polymer networks obtained from simultaneous polymerization of the monomers for two polymeric networks.     

Amino-functionalized pore-expanded SBA-15 for CO2 adsorption

The adsorption of CO₂ on pore-expanded SBA-15 mesostructured silica functionalized with amino groups was studied. The synthesis of conventional SBA-15 was modified to obtain pore-expanded materials, with pore diameters from 11 to 15 nm. Post-synthesis functionalization treatments were carried out by grafting with diethylenetriamine (DT) and by impregnation with tetraethylenepentamine (TEPA) and polyethyleneimine (PEI). The adsorbents were characterized by X-ray diffraction, N₂ adsorption–desorption at 77 K, elemental analysis and Transmission Electron Microscopy. CO₂ capture was studied by using a volumetric adsorption technique at 45 °C. Consecutive adsorption–desorption experiments were also conducted to check the cyclic behaviour of adsorbents in CO₂ capture. An improvement in CO₂ adsorption capacity and efficiency of amino groups was found for pore-expanded SBA-15 impregnated materials in comparison with their counterparts prepared from conventional SBA-15 with smaller pore size. PEI and TEPA-based adsorbents reached significant CO₂ uptakes at 45 °C and 1 bar (138 and 164 mg CO₂/g, respectively), with high amine efficiencies (0.33 and 0.37 mol CO₂/mol N), due to the positive effect of the larger pore diameter in the diffusion and accessibility of organic groups. Pore-expanded SBA-15 samples grafted with DT and impregnated with PEI showed a good stability after several adsorption–desorption cycles of pure CO₂. PEI-impregnated adsorbent was tested in a fixed bed reactor with a diluted gas mixture containing 15 % CO₂, 5 % O₂, 80 % Ar and water (45 °C, 1 bar). A noteworthy adsorption capacity of 171 mg CO₂/g was obtained in these conditions, which simulate flue gas after the desulphurization step in a thermal power plant.