Microporous materials, which refers to the porous materials with pores of less than 2 nm, have been widely used for heterogeneous catalysis, adsorption, separation, gas storage and other numbers of advanced applications. Their high-profile application is mainly focused in the field of energy and environment research, such as the storage and separation of hydrogen, carbon dioxide and methane. According to the compositions and structures, common microporous materials include molecular sieves, porous carbon materials, metal-organic framework compounds (MOF) and microporous organic polymer (MOP). Due to the diversity of element components and structure characteristics, the number of the microporous materials, which can be synthesized in principle, is considerably large. It is impossible to study these materials only by means of experimental methods. With the rapid development of computing power and numerical methods, the theoretical methods used in the studies of microporous materials not only provide the material properties at the molecular level, but also reveal the micro-scale experimental mechanism. Therefore, it is beneficial for establishing the corresponding relationship between the material structures and their properties, leading to promoting the design and development of novel microporous materials. Currently, the accurate theoretical simulations firstly calculate the intermolecular interactions between the key moiety originated from the microporous material and the target molecule through the computational method of quantum chemistry, thereby acquired the potential energy curve of the system. Then the van der Waals interaction parameters of the force field were fitted. Based on the force field, the processes of gas adsorption in the porous materials were simulated by Grand-Canonical Monte-Carlo (GCMC) method. Good agreements between GCMC simulation results and experimental data for adsorption isotherms and heats of adsorption have been observed in many studies. This paper reviews the theoretical methods recently used in the study of the various microporous materials and the latest theoretical research findings. Moreover, the main problems, development prospects and the direction for future research in the study of microporous materials are pointed out.

As it was firstly reported in 2007, conjugated microporous polymer (CMP) has been constructed by a diversity of conjugation building blocks towards a three-dimensional rigid organic framework with the form of insoluble and infusible solid powders. Although CMP has showed the collective characteristics such as exceptional porosity, stable network structure and versatile functionality for potential applications and broad prospects in many fields, the problem of processability concerning this kind of material has not been overcome yet. To take full advantage of their features and break through the application scopes from adsorption and separation to energy and environment such as photoelectric transformation, sensing and catalysis, modulation of growth and formation of CMP in multiple scales is highly anticipated, giving rise to the micro/nanometer-size CMP microspheres and macroscopic CMP films, coatings or gels. Unambiguously, such well-organized forms either have the improved solution properties for further processing, or appear membranes directly assembled into devices. Looking back at the progress of CMP studies in recent years, there are four strategies reported to explore multi-scale CMPs, including (1) soluble CMP-like polymer, (2) solution-dispersible CMP microspheres, (3) CMP-based (composite) film, and (4) CMP-supporting organogel. In these studies, the novel polymerization methods, new catalysts or functional monomers were adopted; the resulting CMPs could be processed, assembled or combined with other materials in solution, and have greatly promoted the performances of optical sensing, photoelectric conversion, energy storage and heterogeneous catalysis on intended devices. It is noted that the reported methodologies have some limitation, but upon the creative ideas and vast explorations, CMP is going to be one important branch of porous materials with promising perspectives.

In this report, a series of N-doped porous carbon materials were successfully prepared from nitrogen-containing porous organic framework JUC-Z2. Compared to original JUC-Z2, the carbonized samples show obviously enhanced gas uptake and isosteric heats of adsorption (Q_st for short). Among the carbonized samples, JUC-Z2-900 shows high CO₂ uptake of 113 cm³·g^-1 at 273 K and 1 bar and H₂ sorption of 246 cm³·g^-1 at 77 K and 1 bar, surpassing most reported porous materials. Especially for CH₄ sorption, a large sorption amount of 60 cm³·g^-1 could be achieved at 273 K and 1 bar. To our best knowledge, this value is comparable to the highest among all the porous materials reported to date. Apart from high gas uptake, the carbon materials also show selective adsorption ability. At 273 K, JUC-Z2-900 shows a high CO₂/N₂ adsorption selectivity of 10 and CO₂/H₂ adsorption selectivity of 66. Raman spectra showed two Raman shifts, the G-band at 1590 cm^-1 is associated with the E_2g mode of graphite, whereas the D-band centered at around 1360 cm^-1 is attributed to the D-band of disordered carbon, corresponding to the defect-induced mode. The intensity of D-band is higher than G-band, indicating a low degree of graphitization. This is also confirmed by powder X-ray diffraction results. X-ray Photoelectron Spectroscopy (XPS) results indicate the nitrogen content is 3.26 wt%, 2.88 wt% and 2.19 wt% for JUC-Z2-700, JUC-Z2-800 and JUC-Z2-900 respectively. Though the nitrogen content decreased after carbonization, the gas sorption increased greatly. This can be attributed to the increased heat of adsorption of the carbonized samples. First, the narrow pore size after carbonization is beneficial for gas storage. Reports indicate that by tuning the pore sizes to around the kinetic diameter of CO₂, it may be possible to increase the number of double or multiple interactions between the adsorbed CO₂ and the pore walls. Second, the all-carbon-scaffold networks also benefit the gas-adsorbent interaction. Last but not the least, the N-doped framework also devote the high gas uptake. Besides the high gas uptake, the carbon materials exhibit high thermal stabilities and could be stable up to 500 ℃. Based on the above results, the carbon materials show great potential in the fields of CO₂ capture and clean energy storage.

Porous polymers have attracted increasing research interest because of their potential to merge the properties of both porous materials and organic polymers. As a novel class of porous polymers, hierarchical porous polymers (HPPs) that simultaneously possess micro-, meso-, and/or macropores are expected to exhibit the advantage of each class of hierarchical pores in a synergistic manner and thus are currently finding wide applications in many fields including energy, environment, catalysis, adsorption, and medicine. However, easy fabrication of well-defined hierarchical porous polymers remains a great challenge. Herein, we successfully developed a facile and effective procedure of reactive-template induced in-situ hypercrosslinking for fabrication of a novel class of hierarchical porous polymer. The key to this procedure is design and employment of SiO₂ nanospheres containing 4-(chloromethyl)phenyl groups as the reactive templates. The 4-(chloromethyl)phenyl groups on the surface of the reactive SiO₂ nanosphere templates can react with the self-crosslinkable monomer 1, 4-dichloro-p-xylol (DCX) to in-situ form a stable covalent bond at their interface. Such a strong covalent interaction facilitates the hypercrosslinking of DCX onto the surface of SiO₂ nanospheres, thus leading to high monodispersion of SiO₂ nanosphere templates and formation of uniform polymeric coating. The as-prepared HPP contains three types of pores: (i) micropores induced by hypercrosslinking of DCX, (ii) meso-/macroporous network formed through the crosslinking of reactive moiety on the periphery of colliding nanospheres with each other in various directions, and (iii) well-defined macropores obtained by removal of sacrificial silica nanospheres. Furthermore, the hypercrosslinked structure characteristic of HPP ensures good carbonization transformation and nanomorphology stability during heating treatment at high temperatures, leading to the formation of hierarchical porous carbon (HPC). New micropores of about 0.6 nm in diameter are generated during carbonization, possibly because of burn-off of noncarbon elements and carbon-containing compounds or disordered packing of microcrystalline carbon sheets and clusters. These HPP and HPC materials could hold considerable promise in applications as advanced adsorbents, catalyst supports, energy-storage materials and others. We hope that the reactive-template induced in-situ hypercrosslinking strategy may open the doors for preparation of various advanced hierarchical porous materials.

Porous covalent organic materials (COM) are a class of multi-dimensional and multi-functional porous materials, which are built via covalent bond of colorful organic building blocks. COM materials possess inherent optimized pore size allowing ion migration, and high specific surface area, providing the possibility of formation of an electrostatic charge-separation layer, a conjugated system resulting in light-harvesting properties and a highly ordered structure, enabling the formation of conductive paths. In this review, we summary the applications on semiconductor, photolysis of water, solar cell, oxygen reduction reaction in fuel cell, lithium-ion/sulfur battery basing on COM materials. Meanwhile, we also propose the design strategy for photoelectronic materials. Although the development of COMs as photoelectronic materials is still in its infancy, COM materials has being attracting ever-increasing attention and open a new window in this field.

Polycarbazole has rigid backbone and conjugated electron rich system, which are beneficial to form permanent porous materials, enhance interactions between adsorbate and adsorbent, and exhibit intrinsic optical and electrical performance. As a novel kind of porous materials, organic porous polycarbazoles possess high specific surface area and permanent porosity, which have drawn great interests owing to the advantages in synthetic diversity, pore size controllability, optical and electrical properties. The preparation of organic porous polycarbazoles has recently been developed rapidly because of their great potential applications in gas storage, separation, vapor adsorption, catalysis, sensing and organic electronics. As for preparative methods of the organic porous polycarbazoles, carbazole-based oxidative coupling polymerization and Friedel-Crafts alkylation are the representative methods. Some other synthetic methods such as nitrile-based trimerization of aromatic nitriles and classic carbon-carbon coupling polymerization. Recently, a facile method for the preparation of hypercrosslinked organic porous polycarbazoles via FeCl₃-promoted one-step oxidative coupling reaction and Friedel-Crafts alkylation in one pot has also been reported. According to the summarized results of porosity and adsorption performance, micro/mesoporous conjugated polycarbazole with high porosity can be obtained via molecular structure tuning. The Brunauer-Emmett-Teller specific surface area of porous polycarbazole is up to 2440 m²·g^-1. The adsorption performance of some organic porous polycarbazoles not only can be comparable with that of the known porous organic polymers with ultrahigh specific surface area, such as PAF-1 and PNN-4, but also can be competitive with the best reported results for porous organic polymers, activated carbons, and metal-organic frameworks under the same conditions. Herein, recent advance such as synthetic methods, properties, and applications in organic porous polycarbazoles has been reviewed.

Covalent organic porous polymers (COPs) are a kind of novel porous polymers formed by covalent bonds linkage between organic building blocks. They feature intrinsic microporous or mesoporous structures and thus exhibit enormous potential applications in energy, chemicals absorption and separation, photovoltaics, gas storage, heterogeneous catalysis, biochemical sensing and so on. Although many reactions and various monomers are available for their synthesis and the resulted frameworks are robust, many challenges still remain. For example, COPs synthesized via traditional methods are usually amorphous and insoluble, their structures are hardly controlled and it is difficult for further processing. To address these issues, many new kinds of methods and strategies are exploited in recent years, it figures out a new direction towards future development of covalent organic porous polymers. Herein, we will give a brief introduction on some recent important progress made in such area.

Conjugated microporous polymers (CMPs) are attracting increasing attention due to their potential applications in areas such as gas adsorption, separation, heterogeneous catalysis and photoelectron. A series of CMPs based on tetraphenylethylene has been synthesized via Pd-catalyzed Sonogashira-Hagihara coupling reaction. During polymerization, all of the polymer networks precipitated from solution as yellow powders that are totally insoluble in common organic solvents tested because of their highly crosslinked structures. Thermogravimetric analysis indicated that all of the polymer networks are thermally stable up to 400 ℃ in nitrogen atmosphere. The high physicochemical and thermal stability could be attributed to the rigid nature of these aromatic polymers, composed solely of strong carbon-carbon and carbon-hydrogen bonds. The absence of the C≡H stretching peaked at around 3280 cm^-1 and the C—Br stretching peaked at around 500 cm^-1 in the FT-IR spectra for the polymer networks demonstrated that most of the ethynyl and bromine functional groups in the starting materials have been consumed by coupling reaction. Powder X-ray diffraction measurements revealed that all of the polymer networks are amorphous in nature. It was found that the homo-coupled polymer network of TPE-CMP1 from 1,1,2,2-tetrakis(4-ethynylphenyl)ethene shows the highest Brunauer-Emmet-Teller specific surface area up to 1096 m²·g^-1 among the resulting polymer networks. TPE-CMP1 exhibits a CO₂ uptake ability of 2.36 mmol·g^-1 at 1.13 bar and 273 K with a H₂ uptake capacity of 1.35 wt% at 1.13 bar and 77.3 K. All of the polymer networks show high CO₂/N₂ selectivity around 30:1 and high isosteric heat of adsorption for CO₂ up to 27.6 kJ·mol^-1. Given the facile preparation strategy, the high physicochemical and thermal stability, the high surface area, and the outstanding CO₂ sorption performances, these polymer networks are promising candidates for potential applications in post-combustion CO₂ capture and sequestration technology.

In recent years the increasing needs of applications have promoted the evolution of porous organic materials (POPs), which can be constructed by copolymerization of organic monomers based on topology chemistry. The advantages of these materials such as excellent physical and chemical stability, low framework density, various structure features, have made them good candidates in gas storage and separation, catalysis, sensors and so on. In this work, a one-pot synthetic strategy has been developed to construct a series of luminescent microporous organic polymers (LMOPs) by the palladium catalyzed Suzuki-Heck cascade coupling reactions of 4-vinylphenylboronic acid with aromatic halides, such as tetrakis(4-bromophenyl)-methane (TBPM), tris(4-iodophenyl)amine (TIPA), 1,1,2,2-tetrakis(4-bromophenyl)ethene (TBPE) and 2,4,6-tris(4-bromophenyl)-1,3,5-triazine (TBPT). Through the optimized conditions, the Pd(OAc)₂/(o-tol)₃P catalyst exhibits the highest efficiency in such a system. The FTIR measurements combined with the solid state ¹³C NMR are employed to confirm the existence of the resultant functional groups, which further proves the success of such polymerization. The resultant materials show porous features with the N₂ adsorption-desorption measurements, with the BET surface areas ranging from 274 to 552 m²·g^-1. Furthermore, with the incorporation of vinyl groups, the polymers exhibit visible luminescent feature from blue to yellow. Considering the emission behaviours of these polymers, the selective quenching toward picric acid is studied with the comparison of other nitroaromatic analytes. The results show that LMOP-11 has the highest sensing ability among these polymers. LMOP-12 shows excellent reusable ability towards picric acid. Such a one-pot method for the preparation of aromatic halides with 4-vinylboronic acid provides a simple and efficient synthetic mean to produce luminescent microporous organic framework that could be used in the selective sensing of explosives.

Up to now, transformation from metal-organic frameworks (MOFs) to covalent-organic-framework cages (COF-Cages) has never been reported. In this report, we demonstrated an organic cage crystal by transformation from a cyclodextrin MOF, via boronate ester formation reaction of the hydroxy groups of γ-CD inside the MOF, followed by removing of the potassium ions. First, CD-MOF was prepared by reacting γ-CD with potassium hydroxide in aqueous solution, followed by vapor diffusion of methanol into the solution according to a previously reported method. The freshly prepared CD-MOF was first washed with ethanol three times to remove the unreacted reactants, and then added to an ethanol saturated solution of benzene-1,4-diboronic acid (BDBA) in a screw top vial, and kept it at 65 ℃ for three days. Finally, the covalent cross-linked CD-MOF (CL-CD-MOF) was obtained by forming boronic esters between the uncoordinated C(2) and C(3) hydroxy groups of contiguous γ-CD sides in the CD-MOF pores and two boronic acid groups of BDBA. Structure and physical properties of Z-Cages were fully characterized by thermogravimetric analysis (TGA), infrared spectroscopy (IR), powder X-ray diffraction (PXRD), solid-state ¹³C and ¹¹B cross polarization/magic angle spining nuclear magnetic resonance (CP/MAS/NMR) spectroscopy and nitrogen adsorption. The obtained zeolite-type organic cage (Z-cage) displayed a targeted sodalite-type crystalline structure and permanent porosity with the surface area of 862 m²·g^-1. A control experiment, the cross-linked polymers (CL-polymer) formed by coupling of γ-CD and BDBA was done by solvothermal method. The CL-polymer was synthesized by the heating of a 4:1 stoichiometric mixture of BDBA and γ-CD at 90 ℃ for three days in dimethylformamide (DMF). PXRD pattern shows the CL-polymer are crystalline, but totally different with Z-cage. This transformation from crystalline inorganic-organic hybrid framework of MOF to crystalline organic framework provides an opportunity for crystal-to-crystal in porous crystalline materials.

Efficient synthesis and the introduction of functional group are the focus of current research on microporous organic polymers (MOPs). In this report, a series of new covalent triazine-based framework polymers (CTFs) based on fluorene with different substituents (FCTF1～FCTF3) has been synthesized using trifluoromethanesulfonic acid (TFMS) catalyzed cyclotrimerization reactions at room temperature. The chemical structures of the polymers were confirmed by FTIR and elemental analysis. In the FTIR spectra, the nearly absence of peaks at around 2220 cm^-1 along with the emergence of strong triazine absorption bands around 1500, 1360 and 800 cm^-1 indicated qualitatively a high degree of polymerization. Thermogravimetric analysis (TGA) under nitrogen atmosphere revealed a high thermal stability with 5% weight loss at temperature up to 364 (FCTF1), 452 (FCTF2) and 238 ℃ (FCTF3). The solid UV-Vis spectra showed that the polymers could all absorb light from UV to visible light region. In the photoluminescence measurement, FCTF1～FCTF3 exhibited bright blue fluorescence with maximum emission wavelengths at 437 nm, 455 nm and 439 nm respectively. The specific surface areas of the polymers changed dramatically according to the substituent attached to the fluorine unit, with BET surface areas changing from nearly nil (FCTF3) to 621 m²/g (FCTF2) when the substituent changed from butyl to ethyl. Pore size distributions were calculated using nonlocal density functional theory (NL-DFT) and porous polymers FCTF1 and FCTF2 showed main pore sizes in the micropore region. CO₂ adsorption capacities of the polymers were also measured and FCTF1 and FCTF2 showed high CO₂ uptake of 1.7 and 1.8 mmol/g respectively at 273 K/1.1 bar. The isosteric heats of adsorption were calculated from the CO₂ isotherms measured at 273 and 298 K. FCTF1 and FCTF2 showed adsorption heats of 26.4 and 22.7 kJ/mol respectively at the zero coverage, indicative strong binding affinity of the polymers with CO₂. To the best of our knowledge, this is the first report on the substituent effect of fluorene-based CTFs and this research can probably enhance the understanding of the structure-property relationship of porous organic polymer materials.

Hypercrosslinked microporous polymers are currently an important class of porous polymer materials and receiving great interest due to their advantages such as high surface area, moderate synthetic conditions and diverse building blocks. According to the difference between the synthetic methods, hypercrosslinked polymers are mainly prepared by the following three strategies: polymer precursor post-crosslinking, one-step self-polycondensation of multifunctional monomers and external crosslinker knitting rigid aromatic compounds. In this review, we introduce the development of hypercrosslinked polymer in detail as well as investigate various synthetic methods and polymer networks with controlled micro-morphology, the broad practical and potential applications including gas storage, adsorption, separation and heterogeneous catalysis were also discussed. In the end, we talk about the disadvantage of hypercrosslinked polymers and challenges in the future as well as predict the further development on synthesis and application.

Porous materials have been intensively applied in fields of ion exchange, adsorption and separation, host-guest chemistry, etc. The development of porous materials has fundamental and practical significance. Based on the component and constructing bond of porous materials, they include zeolite, mesoporous materials, metal-organic frameworks (MOFs) also known as coordination polymers, and porous organic frameworks (POFs). Compared with other porous materials, POFs could be considered as a new star. POFs are constructed by the designable and tunable organic building units (OBUs) via robust covalent bonds. Therefore, POFs display a series of advantages, such as diverse skeletons, high stability, high surface area, tunable pore, etc. The synthesis procedure could be described as the assembly of building units via specific acting force. In this review, we will introduce the synthetic principles, gas storage, catalysis, and other applications of the advanced POFs.

Porous materials have recently drawn much attention owing to their potential applications in gas storage, separations, and heterogeneous catalysis. As a D_3h-symmetric rigid structure, triptycene and its derivatives can be used as suitable building blocks to prepare porous materials with high porosities. Based on the air-stable hexaammoniumtriptycene hexachloride and hexachlorocyclotriphosphazene, porous polymers (TrpPOP-1 and TrpPOP-2) were prepared via one-step polymerization through N-P linkage. The two polymers were characterized at the molecular level by ¹³C NMR and ³¹P NMR as well as IR. The two polymers possess type I nitrogen gas sorption isotherm according to the IUPAC classification. Both TrpPOP-1 and TrpPOP-2 show permanent microporous nature with the Brunauer-Emmett-Teller specific surface area of 790 and 640 m²·g^-1 and exhibit narrow pore size distribution, with dominant pore size locating at 0.59 and 0.63 nm, respectively. Porous polymers with a narrow pore distribution may interact attractively with small gas molecules through improved molecular interaction. Their gas (hydrogen and carbon dioxide) adsorption capacities were measured based on the obtained gas physisorption isotherms. The hydrogen uptake of TrpPOP-1 is 1.30 wt% at 77 K and 1.0 bar, and the carbon dioxide uptake is up to 16.2 wt% at 273 K and 1.0 bar. The higher carbon dioxide loading capacity of TrpPOP-1 may be attributed to its higher charge density at the nitrogen sites of networks that can facilitate local-dipole/quadrupole interactions with carbon dioxide. Meanwhile, the adsorption capacity of the obtained materials for poisonous and harmful organic vapors such as formaldehyde was also investigated. TrpPOP-2 shows a better formaldehyde uptake, which is 5.5 mg·g^-1 at 298 K. Formaldehyde, as a volatile organic compound, is a major air pollutant indoor, therefore, the uptake performance of TrpPOP-2 for formaldehyde would be very promising to remove harmful indoor air pollutant in the environment.

A novel covalent-linked pH-responsive porous polymer (CPP) was prepared successfully using the tetrahedron tetrakis(4-vinylbenzyl)silane and brominated distyrylpyridine (Br-DSP) as the building blocks via the Heck coupling reaction. The structure of the resulting material was characterized by FTIR, solid-state ²⁹Si MAS NMR, ¹³C CP/MAS NMR and elemental analysis. The material possessed good porosity, the porosity parameters were evaluated by nitrogen adsorption and desorption measurement, thereinto, pore-size distribution (PSD) was characterized by nonlocal density functional theory (NL-DFT). The Brunauer-Emmett-Tellerspecific surface area of CPP was 467 m²·g^-1 and total pore volume of 0.41 cm³·g^-1 by t-plot method, the material also exhibited good CO₂ uptake of 2.96 wt% at 273 K/760 mmHg. The powder X-ray diffraction (PXRD), field emission scanning electron microscopy (FE-SEM) and high-resolution transmission electron microscopy (HRTEM) measurements were used to investigate the porous polymer. CPP exhibited high thermal stability with decomposition temperature at 462 ℃ (10 wt%) by thermogravimetric analysis (TGA). By the introduction of the conjugated structures of distyrylpyridine groups, the porous polymer showed luminescence with the maximum emission at ca. 526 nm in the solid state. Additionally, CPP exhibited an excellent pH-responsive property due to the protonated nitrogen centers of pyridine groups in the porous structure, a linear relation was established between the maximum luminescent emission wavelengths (λ_em) of the porous polymer in buffer solutions and the corresponding pH values in the pH range from 1.00 to 4.50, the correlation coefficient of the straight line was 0.992. Therefore, this porous material can be utilized as an promising fluorescent probe in the rapid test systems.

Porous organic polymers (POPs) have become one of a frontier of the research in recent years. POPs including amorphous (e.g. CMP, HCP, PIM, etc.) and crystalline (e.g. COF) porous organic polymers. Due to their inherent porosity, large specific surface area, light weight and easy functionalization at the molecular level, POPs have recently received significant attention for potential applications in gas storage/separation, organic photoelectric, sensoring and heterogeneous catalysis. Here, this review focus on recent developments of POPs in heterogeneous catalysis. Currently, the research on the application of POPs for heterogeneous catalysis is classified into three sections: (a) “bottom-up” embedding metal-ligand catalyst into POPs for heterogeneous catalysis; (b) the encapsulation of metal nanoparticles into POPs for heterogeneous catalysis; (c) “bottom-up” embedding organocatalyst into POPs for heterogeneous organocatalysis. Benefiting from its structural superiority, these functional POPs exhibit excellent catalytic activity. Reference to the development of homogeneous catalysis, the application of functional POPs for heterogeneous catalysis will also have more room for development.

This article summarizes the recent advance for the construction of supramolecular organic frameworks (SOFs) in aqueous media from rationally designed rigid preorganized building blocks. We first introduce the research background on the design of multitopic molecular monomers for the self-assembly of discrete supramolecular aggregates and polymers. We then describe the formation of less ordered supramolecular polymers from tritopic molecular monomers. In the following section, we show that conjugated rigid triangular building blocks have been successfully applied for the construction of two-dimensional (2D) one-layer SOFs in water. Following this, we further present the design of tetratopic building blocks for the formation of three-dimensional (3D) supramolecular networks in aqueous and organic solvents. Finally, we demonstrate that a 3D porous SOF can be assembled from a preorganized tetrahedral building block in water. For the formation of both 2D and 3D SOFs, the hydrophobically driven encapsulation of the stacked dimer of 4-phenylpyridinium unit in the cavity of cucurbit[8]uril in water plays a key role, and the dimerization of viologen radical cation has also been utilized as driving force for generating a 2D SOF. We also briefly introduce the analytical methods for the characterization of SOFs in solution. In the conclusion section, we make a perspective for the construction of SOFs in solution and their potential applications in guest adsorption and release.