Integrating Levels of Hierarchical Organization in Porous Organic Molecular Materials

Porous organic molecular materials(POMMs)are an emergent class of molecular-based materials characterized by the formation of extended porous frameworks,mainly held by non-covalent interactions.POMMs represent a variety of chemical families,such as hydrogen-bonded organic frameworks,porous organic salts,porous organic cages,C-H···πmicroporous crystals,supramolecular organic frameworks,π-organic frameworks,halogen-bonded organic framework,and intrinsically porous molecular materials.In some porous materials such as zeolites and metal organic frameworks,the integration of multiscale has been adopted to build materials with multifunctionality and optimized properties.Therefore,considering the significant role of hierarchy in porous materials and the growing importance of POMMs in the realm of synthetic porous materials,we consider it appropriate to dedicate for the first time a critical review covering both topics.Herein,we will provide a summary of literature examples showcasing hierarchical POMMs,with a focus on their main synthetic approaches,applications,and the advantages brought forth by introducing hierarchy.

Enhancing the activity,selectivity,and recyclability of Rh/PPh_(3) system‐catalyzed hydroformylation reactions through the development of a PPh_(3)‐derived quasi‐porous organic cage as a ligand

In contrast to heterogeneous network frameworks(e.g.,covalent organic frameworks and metal‐organic frameworks)and porous organic polymers,porous organic cages(POCs)are soluble molecules in common organic solvents that provide significant potential for homogeneous catalysis.Herein,we report a triphenylphosphine‐derived quasi‐porous organic cage(denoted as POC‐DICP)as an efficient organic molecular cage ligand for Rh/PPh_(3) system‐catalyzed homogeneous hydroformylation reactions.POC‐DICP not only displays enhanced hydroformylation selectivity(aldehyde selectivity as high as 97%and a linear‐to‐branch ratio as high as 1.89)but can also be recovered and reused via a simple precipitation method in homogeneous reaction systems.We speculate that the reason for the high activity and good selectivity is the favorable geometry(cone angle=123.88°)and electronic effect(P site is relatively electron‐deficient)of POC‐DICP,which were also demonstrated by density functional theory calculations and X‐ray absorption fine‐structure characterization.

Highly Stable sp^(2) Carbon-Conjugated Porous Organic Cages

The high-yield synthesis of ultrastable porous organic cages(POCs)by facile methods is highly desirable but challenging.Inspired by highly stable sp^(2) carbon-conjugated(C=C)covalent organic frameworks,we used rational design and synthesized the first family of sp^(2) carbon-linked POCs(sp^(2)c-POCs)with triangular prism shapes by a one-step Knoevenagel reaction that is a high yield[2+3]condensation reaction.The stability of sp^(2)c-POC was demonstrated under strenuous conditions involving for example concentrated HCl or saturated NaOH solution.sp^(2)c-POC was used as a robust adsorbent for efficient separation of CO_(2)/CH_(4) or CO_(2)/N_(2) mixtures.In view of their facile synthesis and unique properties,we expect widespread use of these sp^(2) C=C linkages in the development of POC materials.

A tetraaldehyde-derived porous organic cage and covalent organic frameworks:Syntheses,structures,and iodine vapor capture

Dynamic covalent imine reactions between 2,3-dimethoxy-[1,1:4,1-terphenyl]-3,3,5,5-tetracarbaldehyde(DMTT)and cyclohexanediamine,p-phenylenediamine,and benzidine,respectively,generate a porous organic cage(DMPOC)and two covalent organic frameworks(COFs),USTB-29,and USTB-30.DMPOC shows a[3+6]topological cage-like structure according to single crystal X-ray diffraction result.In contrast,both microcrystalline USTB-29 and USTB-30 exhibit two-dimensional monoporous structures in an eclipsed AA stacking style based on powder X-ray diffraction and theoretical simulations.In addition,DMPOC is capable of efficiently absorbing the iodine vapor with an outstanding uptake of 5.10 g/g,much higher than that of USTB-29(3.07 g/g)and USTB-30(3.16 g/g).Cage to COFs transformations have been realized from DMPOC to USTB-29 and USTB-30 via the imine bond exchange with slightly increased iodine vapor uptake.Mechanism investigations uncover that both nitrogen and oxygen atoms of POC and COFs contribute to iodine vapor capture due to the formation of charge transfer matter,and loose interaction introducing adaptive expanding voids of DMPOC is suggested to capture more iodine vapor than that of COFs with strongπ-πinteractions.

Eco-Friendly Encapsulation of Metal Clusters in Porous Organic Cages for Engineerable Microenvironment and Enhanced Catalysis

Developing artificial catalysts that mimic the functionality of enzymes and adapt to the surrounding microenvironment to achieve specific activity and selectivity is a fascinating research area yet remains a great challenge.In this work,we present a meticulously designed strategy for the successful encapsulation of ultrasmall metal clusters(MCs)within an amine-type porous organic cage(POC)through electrostatic complexation,phase transfer,and alcohol reduction processes.The amine cage showcases an intriguing and customizable feature that allows for the regulation of the surrounding microenvironment of the confined MCs through a feasible postmodifi-cation approach.This functionalization of cage skeleton further facilitates precise adjustment to the surface electronic state of Pd cluster,thereby influencing the adsorption behavior of substrate.Consequently,this controlled regulation leads to modified activity and chemoselectivity in the catalytic hydrogenation of halogenated nitrobenzene.Importantly,the investigation of the correlation between the surrounding microenvironment,substrate adsorption,and catalytic performance in the POC-immobilized MCs system has not been previously reported.We anticipate that our research will provide valuable insights in this field.

Phosphine-Built-In Porous Organic Cage Supported Ultrafine Pd Nanoclusters Enable Highly Efficient and Regioselective Hydrogenation of Epoxides

Selective hydrogenation of epoxides has been regarded as an atom-economical and straightforward method for the synthesis of alcohols.However,it remains a big challenge in the precise control of regioselectivity.To date,the reaction enabled by a reusable and high-performance heterogeneous catalyst with excellent regioselectivity is very scarce.Herein,we develop highly loaded and ultrafine Pd nanoclusters(NCs)encapsulated on a phosphinebuilt-in porous organic cage(FPPOC)for the catalytic hydrogenation of epoxides by molecular hydrogen.Benefiting from the unique characters of uniform dispersion and strong interaction between Pd NCs and FPPOC,the resultant Pd NCs exhibited superior catalytic activity and excellent regioselectivity for the hydrogenation of epoxides under milder conditions.A diverse set of terminal and internal epoxides was efficiently reduced to the corresponding linear or branched alcohols in an extremely regioselective manner,well tolerating diverse functional groups.Remarkably,the catalyst demonstrates high stability and could be reused up to 10 times with marginal decay in activity and regioselectivity.Furthermore,the catalyst is applicable for scale-up synthesis with a record turnover number as high as 16,111,to the best of our knowledge,outperforming those previous state-of-the-art catalysts.Control experiments and characterizations in combination with density functional theory calculations provide insight into the superior activity and excellent regioselectivity.

Robust Giant Octahedral[6+8]Porous Organic Cages for Efficient Ethylene/Ethane Separation

The exploration of ethane(C_(2)H_(6))-selective porous materials for the direct production of polymer-grade ethylene(C_(2)H_(4))from a C_(2)H_(6)/C_(2)H_(4) mixture in a single energy-saving adsorption step is of utmost importance but remains a significant challenge.Thus,developing robust C_(2)H_(6)-selective adsorbents with high C_(2)H_(6) capacity and C_(2)H_(6)/C_(2)H_(4) selectivity is urgently needed for industrial applications.In this study,we have successfully designed and synthesized two novel calix[4]resorcinarene-based porous organic cages(POCs)named CPOC-501 and CPOC-502.The POCs were formed via a Schiff-base reaction involving face-directed[6+8]condensation between a bowlshaped tetratopic tetraformylcalix[4]resorcinarene and triangular tritopic amine synthons.Analysis using single crystal X-ray crystallography revealed that both cages possess large truncated octahedral cavities with a volume of approximately 6500Å3 and 12 accessible rhombic windows with a side length of approximately 10.5Å.Furthermore,the cages exhibited excellent chemical stability under neutral,acidic,and basic conditions and high Brunauer–Emmett–Teller specific surface areas of up to 2175 m^(2) g^(−1) after desolvation.Both POCs demonstrated superior adsorption capabilities for C_(2)H_(6) over C_(2)H_(4).Notably,CPOC-502 exhibited a C_(2)H_(6) capacity and C_(2)H_(6)/C_(2)H_(4) selectivity of 83 cm^(3) g^(−1) and 2.83,respectively,surpassing most of the best-performing C_(2)H_(6)-selective porous organic materials reported to date.Moreover,breakthrough experiments confirmed that both cages efficiently produced polymer-grade C_(2)H_(4)(>99.9%)directly from the C_(2)H_(6)/C_(2)H_(4) mixture,highlighting their outstanding recyclability.

Porous organic cages as a novel platform for second harmonic generation

Second harmonic generation(SHG) is one of the most extensively applied nonlinear optical phenomena. Compared to traditional inorganic SHG materials, organic SHG materials, including non-centrosymmetric small molecular crystals and organic polymers, have been extensively explored for SHG optics due to their advantageous properties, including high light-induced damage threshold, ultrafast response speed, high polarization ratio, wide transparency range, and elevated dielectric constant. However,in organic SHG materials, most small molecular crystals often show poor thermal stability(<200 ℃) due to their low molecular weight, which is an important obstacle for practical application under high temperatures. On the other hand, the difficulty in the growth of large-size crystals as well as the disorderly array of chromospheres on polymer chains associated with organic polymers have hindered their widespread application in SHG due to the requirements of processability and homogeneity.Therefore, it is significantly necessary to develop novel organic SHG material with high thermal stability, large-size crystals,excellent processability, high homogeneity, and a well SHG effect. In the contribution, we developed herein porous organic cages(POCs) as a novel platform for SHG optics. Thanks to its inherent macromolecular composition and zero-dimensional discrete structures, POCs can not only solve the instability problem of small molecule crystals but also overcome the drawbacks in growing large-size crystals for organic polymer. The obtained two POCs with chiral asymmetric centers(CPOC-R-5 and CPOCS-7) display advantageous features for SHG optics including well SHG performance, large-size crystal(5 mm×3 mm×1 mm),high thermal stability(≥250 ℃), wide transparency window(750–2,000 nm) and high polarization ratio(up to 94.5%). This work thus develops POCs as a new platform toward the construction of organic NLO materials with the potential application in sorts of SHG optics.

手性多孔有机笼用作气相色谱固定相分离手性和非手性化合物

多孔有机笼(POCs)是一种新型的多孔分子材料,具有明确的分子内腔结构、丰富的主客体识别能力和良好的溶解性,因而在分子识别、气体吸附、传感、催化、色谱分离等多个领域受到广泛关注。本文由四(4-醛基苯基)乙烯和(R,R)-1,2-环己二胺通过席夫碱缩合反应合成了一种手性多孔有机笼(CPOC),采用静态涂敷法将其涂敷于毛细管柱内表面制备了气相色谱柱,测试了该柱对有机混合物、异构体以及手性化合物的分离能力。结果显示,该柱可以实现4种有机混合物(正构烷烃、芳香烃、正构醇和Grob混合物)中所有组分的基线分离;同时有9种二取代苯位置异构体以及包括结构异构和顺反异构在内的16种有机异构体在该柱上也获得了较好的分离。更重要的是,该柱还具有优秀的手性拆分性能,有12种手性化合物在该柱上得到了拆分,其中5种手性化合物(3-羟基丁酸乙酯、缬氨酸衍生物、谷氨酸衍生物、1,2-丁二醇二乙酸酯和1,2-环氧丁烷)获得了基线分离。将该柱与商品β-DEX 120柱的拆分效果相比,该柱可以拆分β-DEX 120柱不能拆分的3-羟基丁酸乙酯、缬氨酸衍生物、谷氨酸衍生物、1,2-环氧丁烷、环氧氯丙烷和环氧溴丙烷等6种手性化合物,说明其与β-DEX 120柱具有手性拆分互补性。研究表明,CPOC制备的毛细管柱对手性和非手性化合物都具有良好的分离能力。

多孔有机笼配体的合成及催化性能研究

文章通过两步反应简单高效地制备出目标多孔有机笼RCC3,将其作为配体和CuBr_(2)配位构建多孔有机笼配合物RCC3@Cu。采用X-射线衍射(X-ray diffraction,XRD)和电喷雾电离质谱(electrospray ionization mass spectrometry,ESI-MS)表征RCC3@Cu的结构与组成,结果表明,RCC3@Cu配位稳定,有望用于介导原子转移自由基聚合(atom transfer radical polymerization,ATRP)。采用RCC3配体介导甲基丙烯酸甲酯(MMA)的ATRP,2 h其转化率达到80%,聚合物分散性指数(polymer dispersity index,PDI)为1.15;最终转化率为98.5%,PDI为1.16。聚合动力学显示RCC3介导的ATRP为近似一级反应动力学,符合活性聚合特征。该文研究RCC3配体介导不同类型单体的聚合,验证了RCC3配体具有单体泛用性。研究结果表明,RCC3体可有效应用于ATRP催化,有进一步研究价值。

多孔有机笼的制备及其用作毛细管电色谱手性固定相

多孔有机笼(POCs)是具有一类内在的、客体可及的空腔的离散分子,是一类独特的微孔材料。本文根据席夫碱反应原理,用(1 R,2R)-二氨基环己烷和3,3′,5,5′-四醛基-4,4′-联苯二酚缩合成一种孔径均匀、高比表面积、热化学稳定性良好的棱柱形手性多孔有机笼(POCs)。采用核磁共振氢谱仪、红外光谱、热重分析和扫描电子显微镜对该材料进行表征。将该材料溶解在二氯甲烷中,用动态涂覆法将溶液均匀地涂覆在石英毛细管内壁上,制成毛细管电色谱柱。结果表明,该手性电色谱柱不仅能拆分氧氟沙星、特罗格尔碱、2-氨基-1-丁醇和1-苯基-1-戊醇4种手性药物,还能拆分o,m,p-甲苯胺和o,m,p-氯苯胺2种位置异构体,说明该手性柱具有良好的手性分离能力。通过研究氧氟沙星、特罗格尔碱、2-氨基-1-丁醇和1-苯基-1-戊醇的最佳拆分条件,得出电压、缓冲溶液浓度和pH值对组分分离度有显著影响,其中,氧氟沙星、特罗格尔碱、2-氨基-1-丁醇的最优分离电压均为15 kV,1-苯基-1-戊醇的最佳分离电压为17 kV;氧氟沙星、特罗格尔碱、2-氨基-1-丁醇、1-苯基-1-戊醇的最佳缓冲液浓度均为0.100 mol/L,pH为7.5。在最佳的分离条件下,该电色谱柱拆分氧氟沙星、特罗格尔碱、2-氨基-1-丁醇和1-苯基-1-戊醇的分离度分别为1.80、3.33、1.69、1.18,都获得了较好的分离效果。可见,POCs是一种良好的手性毛细管电色谱固定相,有一定的手性拆分能力,在色谱分离中具有良好的应用前景。

Post-synthetic metalation of organic cage for enhanced porosity and catalytic performance

Porous organic cages(POCs)have shown great potential in many applications,and post-synthetic modification(PSM)has been confirmed to be an effective strategy to tailor their structures and related functionalities.However,it is extremely challenging to develop a general platform for simple-to-make functional POCs for advanced applications by PSM method.Herein,we reported that octahedral calix[4]resorcinarene-based hydrazone-linked porous organic cage(HPOC-401)provides an excellent platform for post-synthetic metalation by various transition metal(TM)ions under mild conditions due to the abundance of coordination sites in its skeleton.Such metalated products(HPOC-401-TM)exhibit Brunauer-Emmett-Teller(BET)surface area up to1,456 m^(2)g^(-1),much higher than that of the pristine HPOC-401,which has a BET value of 474 m^(2)g^(-1).Moreover,the metalation and porosity increases further influence their gas capture,separation,as well as catalytic performance.For instance,HPOC-401-TM products exhibit higher CO_(2),H_(2),and C2 hydrocarbon gas uptake,as well as higher C_(2)H_(6)/C_(2)H_(4) selectivity than HPOC-401.Moreover,the HPOC-401-TM also shows better catalytic performance in the cycloaddition of CO_(2) with epoxides compared to HPOC-401.These findings uncover a simple yet effective approach for modifying the porosity characteristics of organic cages,which will undoubtedly expand their future implementations.

Assembling ionic liquid into porous molecular filler of mixed matrix membrane to trigger high gas permeability,selectivity,and stability for CO_(2)/CH_(4) separation

As an emerging zero-dimensional nano crystalline porous material,porous organic cages(POCs)with soluble properties in organic solvents,are promising candidates as molecular fillers in mixed matrix membranes(MMMs).The pore structure of POCs should be adjusted to trigger efficient gas separation performance,and the interaction between filler and matrix should be optimized.In this work,ionic liquid(IL)was introduced into the molecular fillers of CC3,to construct the IL@CC3/PIM-1 membrane to effectively separate CO_(2) from CH_(4).The advantages of doping IL include:(1)narrowing the cavity size of POCs from 4.4 to 3.9Åto enhance the diffusion selectivity,(2)strengthening the CO_(2) solubility to heighten the gas permeability,and(3)improving the compatibility between filler and matrix to upgrade membrane stability.After the optimization of the membrane composite,the IL@CC3/PIM-1-10%membrane possesses the CO_(2) permeability of 7868 Barrer and the CO_(2)/CH_(4) selectivity of 73.4,which compared to the CC3/PIM-1-10%membrane,improved by 15.9%and 106.2%,respectively.Furthermore,the membrane has maintained a stable separation performance at varied temperatures and pressures during the long-term test.The proposed method offers an efficient way to improve the performance of POCs-based MMMs in gas separation.

An Allochroic Molecular Cage Switch for Sensing and Capturing Organic Pollutants

The adsorption method is considered to be one of the most promising organic pollutants emission reduction strategies.The design and synthesis of high-performance porous adsorbents are one of the most important but challenging works.In this work,we constructed a new class of porous molecular cage switches by a simple reaction using phenolphthalein as the raw material.The molecular cage switches displayed interesting on-off behavior towards organic guests,which is highly responding to organic pollutants with rapid color change and is also able to adsorb these organic pollutants through an open-to-close pathway.This molecular cage switch also has excellent regenerative cycling properties and water resistance,which is expected to be employed in the handling of organic pollutants in the future.

Dimeric Calix[4]resorcinarene-based Porous Organic Cages for CO_(2)/CH_(4) Separation

Investigating gas separation by emerging porous organic cage(POC) solids is still on its initial stage. In this work, two novel [2+4] organic cages with distinguished structures have been prepared based on the Schiff-based condensation reaction between tetraformyl-functionalized calix[4]resorcinarene building blocks and xylylenediamine(XDA) isomers. Specifically, the use of para-position XDA affords lantern-shaped cage(CPOC-105) with a medium cavity of ca. 0.526 nm^(3), while the meta-position produces peanut-shaped structure(CPOC-106) with two small cavities of ca. 0.181 nm^(3). Both CPOC-105 and CPOC-106 exhibit high selectivity capture of CO_(2) over CH4 with calculated selectivity coefficients of 4.5 and 3.1, respectively, under ambient conditions, and are capable of separating CO_(2)/CH_(4) mixtures by fixed-bed column breakthrough experiments.

Porous Pyrene Organic Cage with Unusual Absorption Bathochromic-Shift Enables Visible Light Photocatalysis

We have constructed a novel porous pyrene-based organic cage,PyTC1,through the condensation reaction of cyclohexanediamine with 5,5′-(pyrene-1,6-diyl)diisophthalaldehyde.Single-crystal X-ray diffraction analysis reveals the effective intercage C–H...πinteraction between cyclohexanediimine and pyrene segments.Such a soft intercage C–H...πinteraction,rather than a classic J-aggregate with slippedπ–π-stacking configuration,induced an unusual bathochromic shift of pyrene-based chromophore absorption from an ultraviolet region of PyTC1 in solution to the visible light region of PyTC1 in solid-state.

水稳定的多孔有机分子笼

近十几年来,多孔有机分子笼(POCs)发展迅速,其在有机溶剂中具有良好的溶解性,被广泛应用于主客体的包封、分子分离、催化和气体吸附等方面.但通常POCs结构在水溶液中不稳定,限制了其在水环境中应用.因此,了解POCs在水环境中不稳定的原因以及构建水稳定的POCs是拓展其应用范围的关键.文章综述了构建水稳定POCs的5种方法及其应用,为以后其在水环境中的研究创造了更广阔的应用前景.

多孔有机笼毛细管电色谱手性柱的制备及应用

多孔有机笼(POCs)是一种新型的具有稳定有序三维空腔结构的多孔材料。通过2-羟基-1,3,5-均苯三甲醛与1R,2R-1,2-二苯基乙二胺发生席夫碱的缩合反应,合成了一种具有羟基功能基团的单一手性POCs材料;将其均匀涂敷在毛细管壁上制成色谱柱,利用电色谱柱成功拆分了二氢黄酮、吡喹酮、萘普生和3,5-二硝基-N-(1-苯乙基)苯甲酰胺4种手性化合物。探究了分离电压、缓冲溶液浓度及其pH值等因素对手性拆分的影响,获得了4种手性物质在POCs色谱柱上的最佳拆分条件。实验研究表明,二氢黄酮、吡喹酮、萘普生和3,5-二硝基-N-(1-苯乙基)苯甲酰胺获得优化分离效果所需的工作电压分别为13、14、14和12 kV;二氢黄酮适宜Tris-H_(3)PO_(4)缓冲溶液浓度为0.075 mol/L,吡喹酮、萘普生和3,5-二硝基-N-(1-苯乙基)苯甲酰胺适宜Tris-H_(3)PO_(4)缓冲溶液浓度为0.100 mol/L;4种手性物质得到最佳分离效果时的pH值均为3.51。二氢黄酮、吡喹酮、萘普生和3,5-二硝基-N-(1-苯乙基)苯甲酰胺均达到基线分离,分离度分别为2.99、2.10、2.58和3.59。该POCs色谱柱还成功拆分了o,m,p-碘苯胺、o,m,p-硝基苯胺两种位置异构体。该研究表明POCs手性电色谱柱具有良好的手性识别能力,是一种优秀的手性分离材料,具有很大的电色谱手性分离应用前景。