Liquid chromatography of polymer mixtures applying a combination of exclusion and full adsorption mechanisms. 5. Six-component blends of chemically similar polymers

The separation of six-component blends of chemically similar homopolymers utilising the full adsorption-desorption (FAD) process is presented. The main advantage of the FAD approach over other methods represents the successive and independent size- exclusion chromatography (SEC) characterisation of all blend components. The method is based on the full adsorption and retention of all n or n−1 components of the polymer blend from an adsorption promoting liquid (ADSORLI) in a small FAD column. Nonadsorbed macromolecules are forwarded directly into SEC for molecular characterisation. Next, appropriate displacers are successively applied to the FAD column to selectively release preadsorbed blend constituents into the on-line SEC column. Dynamic integral desorption isotherms for single constituents, as well as for polymer blends to be analysed, allow identification of optimal displacer compositions to release just one kind of macromolecule. Model polymer blends containing polystyrene (PS), poly(lauryl methacrylate), poly(butyl methacrylate), poly(ethyl methacrylate), poly(methyl methacrylate) and poly(ethylene oxide) (PEO) or, alternatively, PS, poly(2-ethylhexyl acrylate), poly(butyl acrylate), poly(ethyl acrylate), poly(methyl acrylate) and PEO of similar molar masses can be separated and characterised in one multistep run using nonporous silica FAD packing, toluene as an ADSORLI and its mixtures with a desorption promoting liquid such as ethyl acetate, tetrahydrofuran or dimetylformamide to form displacers with appropriate desorption strength. Received: 9 September 1998 Accepted in revised form: 16 November 1998     

Reconcentration of diluted polymer solutions by full adsorption/desorption procedure: II. Desorption of macromolecules by a narrow pulse of displacer

Diluted polymer solutions can be effectively reconcentrated applying full adsorption/desorption processes. Macromolecules from diluted solutions are quantitatively retained within a bed of appropriate adsorbent. Next, the polymer is released by a high‐strength desorbing liquid that is introduced into the sorbent bed as a narrow pulse. To evaluate the above reconcentration procedure, medium‐polarity polymers, mainly poly(methyl methacrylate)s of various molar mass distributions were chosen as model species. Nonporous silica was used as an adsorbent, toluene and chloroform as adsorbing liquids, and tetrahydrofuran as a desorbing liquid in an HPLC‐like apparatus. The concentration profiles of both the desorbing liquid pulse and desorbed polymer were monitored with the usual LC detectors. On‐line size exclusion chromatography was employed in selected cases to determine molar mass and molar mass distribution of desorbed macromolecules. The effect of some experimental parameters on the reconcentration efficiency was elucidated, viz. the nature of the sample solvent‐adsorbing liquid, flow rate of desorbing liquid, molar mass, molar mass distribution, and nature of reconcentrated polymer, as well as relations among the amount of the polymer to be reconcentrated and the volume of the desorbing liquid pulse. It is shown that very high reconcentration factors can be readily obtained by the full adsorption–desorption procedure if the experimental conditions are carefully optimized. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 267–275, 1999     

Role of adsorption in liquid chromatography of macromolecules and potential of liquid chromatography in assessing adsorption of macromolecules onto solid surfaces

Many liquid chromatographic (LC) separations of macromolecules are influenced or directly based on adsorption of solutes on column packing. In the case of well known size exclusion chromatography (SEC), adsorption effects are usually unwanted and therefore suppressed. Still they appear in many SEC systems and may badly affect precision of results obtained. In other LC methods applicable to high polymers, adsorption is deliberately combined with exclusion. The aim is to discriminate complex polymer systems which exhibit more than one single distribution of their molecular characteristics. The main goals of such combinations include either a controlled increase or a full suppression of separation selectivity according to one molecular characteristics. Most important so far known exclusion-adsorption compensation methods allowing to suppress dependence of LC retention volumes on polymer molar mass are reviewed. The discussion is accomplished with a presentation of newly developed full adsorption - desorption (FAD) method which can be combined with various LC procedures. A very useful combination represents the on-line FAD/SEC procedure which enables also to study adsorption and desorption phenomena in the systems solid surface - solvent - macromolecules.     

Liquid chromatography of polymers under limiting conditions of desorption II. Tandem injection and quantitative molar mass determination

Liquid chromatography under limiting conditions of desorption (LC LCD) is a method which allows molar mass independent elution of various synthetic polymers. A narrow, slowly moving zone of small molecules, which promotes full adsorption of one kind of polymer species within column (an adsorli) acts as an impermeable barrier for the fast moving macromolecules. The latter accumulate on the barrier edge and elute nearly in total volume of liquid within column. At the same time, transport of less adsorptive macromolecules is not hampered so that these are eluted in the size exclusion (SEC) mode. As result, polymers differing in their polarity and adsorptivity can be easily separated without molar mass interference. Three methods of barrier creation are discussed and compared. It is shown that a fraction of sample may elute unretained if the adsorli sample solvent is used as a barrier in connection with a narrow-pore column packing. One part of excluded macromolecules likely breaks-out from the adsorli zone and this results in partial loss of sample and distortion of the LC LCD peaks. This problem can be avoided if the adsorli zone is injected immediately before sample solution. Applicability of the LC LCD method for polymer separation has been demonstrated with a model mixture of poly(methyl methacrylate) (adsorbing polymer) and polystyrene (non adsorbing polymer) using bare silica gel as a column packing with a combination of tetrahydrofuran (a desorption promoting liquid -a desorli) and toluene (adsorli). It has been shown that the LC LCD procedure with tandem injection allows simple and fast discrimination of polymer blend components with good repeatability and high sample recovery. For quantitative determination of molar masses of both LC LCD and SEC eluted polymers, an additional size exclusion chromatographic column can be applied either in a conventional way or in combination with a multi-angle light scattering detector. A single eluent is used in the latter column, which separates the mixed mobile phase, system peaks and the desorli zone from the polymer peaks so that measurements are free from disturbances caused by the changing eluent composition. The resulting LC LCD x SEC procedure has been successfully applied to poly(methyl methacrylate) samples.     

Evaluation of high-performance liquid chromatography column retentivity using macromolecular probes. II. Silanophilic interactivity traced by highly polar polymers

A new method of HPLC column retentivity testing utilizes polymeric probes instead of conventional sets of low molar mass substances. The procedure allows at least semiquantitative, separate and independent evaluation of adsorption and partition properties of column packings. In this present work, the method is applied for comparison of the polar interactivities of selected silica gel C18 HPLC columns. It is shown that free silanols which remained on the surface of the end-capped silica C18 column packings are accessible for interaction with highly polar macromolecules. High molar mass polymeric test probes are adsorbed on the surface silanols and their retention volumes increase. As result, deviations from regular size-exclusion chromatographic (SEC) behavior are observed. The extent of retention volume changes depends on both the nature of polymer probes and on column packing type. Adsorption of macromolecules can be suppressed by addition of a highly polar substance to the mobile phase. The amount of polar additive which is needed to attain regular SEC elution of the polymer probe depends on the column packing type and can be used as a characteristic of silanophilic column interactivity. Courses of dependences of retention volumes on sizes of macromolecules indicate the presence of "U-turn" adsorption which allows two and more silanols situated among C18 groups to be occupied simultaneously with the same macromolecule.     

Non-equilibrium adsorption at solid/liquid interfaces from polyelectrolyte solutions

The poly(2-vinylpyridine) layer was established at the Pyrex glass/water interface with periodic phases of adsorption/desorption runs observed over several days. This was evidenced by determining the concentration of radio-labelled molecules in the solution equilibrating the glass beads as a function of time (the effluent) while the same radio-labelled polymer was slowly supplied by injecting the polymer solution into the reactor containing the adsorbent at a controlled extremely slow rate. Although the adsorption (or the desorption) steps seemed to present some periodic character, they were better correlated with the successive bulk concentration thresholds that were established with time when the initial surface was free of polymer at time zero. Even when the adsorbent was coated at different degrees, desorption steps were correlated to the overstepping of decreasing concentration thresholds. Adsorption and desorption runs were attributed to the existence of different typical interfacial conformations of the adsorbed macromolecules that only can be stabilised in the adsorbed state when the layer was equilibrated with the polymer solution of a certain concentration. Macromolecule were definitely adsorbed when the reconformation process led to a flat conformation (trains). Macromolecules adsorbed with a conformation close to their solution conformation may be desorbed as a result of the reconformation process affecting previously adsorbed neighbour molecules (in the case of partially coated surfaces at time zero of injection). Macromolecules with loops and tails were retained on the surface when the polymer concentration in the bulk was progressively increased (for uncoated surfaces at time zero of injection). All these effect were attributed to the combined influence of topological effects on adsorption and reconformation of adsorbed macromolecules that characterise the non-equilibrium adsorption processes.     

Studies on high-performance size-exclusion chromatography of synthetic polymers. I. Volume of silica gel column packing pores reduced by retained macromolecules

Macromolecules, which stay adsorbed within the active size-exclusion chromatography (SEC) column packings may strongly reduce effective volume of the separation pores. This brings about a decrease of retention volumes of the non-retained polymer samples and results in the increased apparent molar mass values. The phenomenon has been demonstrated with a series of poly(methyl methacrylate)s (PMMA) and a polyethylenoxide (PEO) fully retained by adsorption within macroporous silica gel SEC column from toluene or tetrahydrofuran, respectively. The non-retained probes were polystyrenes (PS) in toluene and both PS and PMMA in THF eluents. The errors in the peak molar mass values determined for the non-retained polymer species using a column saturated with adsorbed macromolecules and considering calibration curves monitored for the original "bare" column packing assumed up to several hundreds of percent. Errors may appear also in the weight and number averages of molar masses calculated from calibration dependences obtained with columns saturated with adsorbed macromolecules. Moreover, the SEC peaks of species eluted from the polymer saturated columns were broadened and in some cases even split. These results demonstrate a necessity not only to periodically re-calibrate the SEC columns but also to remove macromolecules adsorbed within packing in the course of analyses.     

Dynamic alterations of fibronectin layers on copolymer substrates with graded physicochemical characteristics

Desorption and exchange of preadsorbed fibronectin layers in pure buffer solution and solutions of human serum albumin or fibronectin, respectively, were studied in dependence on the physicochemical characteristics of maleic acid copolymer films used as substrates. Although the preadsorbed amount of fibronectin differed only slightly, the protein was found to exhibit a significantly enhanced anchorage at the more hydrophobic polymer surface as compared to the more hydrophilic and more negatively charged polymer surface. The preadsorbed fibronectin layer was most efficiently exchanged by fibronectin (i.e., in the homodisplacement process) while pure buffer solution and human serum albumin solutions induced desorption or exchange of fibronectin to lower and similar degrees. An increase of the total adsorbed amount of protein due to additional adsorption of fibronectin or human serum albumin accompanied the partial exchange of the preadsorbed fibronectin in the displacement experiments. Evaluation of the kinetics of desorption and exchange of fibronectin at any of the substrates revealed two kinds of surface-attached protein populations--a fast desorbing species and a species with a slow desorption and exchange rate. By a multivariate regression analysis the surface characteristics of the polymer substrate were confirmed to determine the degree of protein desorption and exchange while the dynamics of the layer alteration was found to solely depend on the diffusion behavior of the proteins.     

Liquid chromatography of synthetic polymers under critical conditions of enthalpic interactions 4: Sample recovery

Reduced sample recovery is a frequent feature of LC of macromolecules under critical conditions of enthalpic interactions (LC CC). Several methods of assessment of LC CC sample recovery are compared. A novel approach is based on an online combination of the. The LC CC column with a noninteractive SEC column. It provides not only the amount but also the molar mass of the eluted/withheld polymer. The procedure was tested with poly(methyl methacrylate), bare silica gel column packings, and “critical eluent” tetrahydrofuran/toluene. It was shown that macromolecules with higher molar masses were preferentially trapped within the LC CC column packing so that the eluted part of the sample was no longer representative. The incomplete polymer elution can make the LC CC polymer analyses susceptible to significant experimental errors.     

Strategies in two‐dimensional liquid chromatographic separation of complex polymer systems

Complex synthetic polymer systems as for example copolymers exhibit distributions in at least two of the three basic molecular characteristics which are molar mass, chemical structure/composition and molecular architecture. Size exclusion chromatography (SEC) separates macromolecules according to their size in solution which simultaneously depends on all molecular characteristics. Therefore, multi‐dimensional liquid chromatographic techniques are to be applied to independently assess all different distributions present in the sample. So far, two‐dimensional separations have been attempted. In the first dimension separation column, selected liquid chromatographic mechanisms are intentionally combined to suppress effects of all but one molecular characteristic. Consequently, polymer species are separated exclusively or at least predominantly according to one single parameter. In the second dimension separation column, macromolecules are separated according to another molecular characteristic. In this contribution the methods are briefly reviewed in which effect of polymer molar mass on polymer retention is suppressed. The resulting ”one parameter separation systems” can be on‐line or off‐line connected to another separation system such as SEC to provide more detailed characterization of complex polymers. Besides, selected procedures for the re‐concentration of diluted polymer solutions are concisely treated. These may be utilized for increasing the concentration of sample(s) leaving the first dimension separation column. Eventually, some arrangements for controlled sample re‐introduction into the second dimension separation column are outlined.     

Enthalpy assisted size exclusion chromatography. Part 2. Adsorption retention mechanism

A novel high performance liquid chromatographic method for separation of synthetic polymers has been tested. It involves combination of the enthalpic and entropic retention mechanisms, resulting in increased selectivity of separation within a specific molar mass range. In this present case, the enthalpic retention mechanism is adsorption of macromolecules on a bare silica gel column packing. Under critical conditions of enthalpic interactions, homopolymers are known to elute irrespective of their molar mass. However, in the vicinity of critical conditions, a situation can be identified when retention volumes (V(R)) rapidly decrease with increasing molar mass. Typically, this happens for polymer species close to or above their exclusion limit observed with the same column in the absence of enthalpic interactions between macromolecules and packing, that is near "ideal SEC" conditions. The dependence of polymer retention volume on molar mass closely resembles size exclusion conditions. However, the witnessed rate of change in V(R )with polymer molar mass is more pronounced, thus indicating increased selectivity of separation. This situation not only offers the benefit of more selective separation according to molar mass but efficient discrimination of macromolecules possessing different nature and interactivity with the column packing can be accomplished as well.     

Liquid chromatography of macromolecules at the critical adsorption point. II. Role of column packing: Bare silica gel

Liquid chromatography of macromolecules at the critical adsorption point (LC CAP) presents a potentially very powerful method for molecular characterization of complex polymers. However, LC CAP applicability is limited due to various experimental problems. The pore sizes and surface chemistry of the column packings belong to the most important weak points of the method. The LC CAP behavior of poly(methyl methacrylate)s was investigated using bare silica gels of 6, 12, and 100 nm pore sizes and with various amounts of surface silanols. Tetrahydrofuran as the adsorption suppressing liquid and toluene as the adsorption promoting liquid were mixed to form the “nearly critical” eluents. Both pore size and surface chemistry of silica were found to strongly influence the retentive characteristics of the system in the critical adsorption area. Macromolecules that were large enough to be excluded from the packing pores hardly followed the LC CAP rules: their retention volumes changed irregularly with the polymer molar mass and their recovery dropped sharply. The narrow pore silica gel-packed column governed the elution patterns of the whole column set composed of silica gels with different pore sizes. This makes the conventional LC CAP characterization of common polymers with broader molar mass distribution impractical and even not feasible. A hybrid column system was proposed containing narrow pore nonadsorptive column added in series to the meso- and macroporous LC CAP silica gels. This narrow pore column would allow separation of gas, impurities, and system peaks from the polymer peaks. The possible successive changes of the surface of silica gel, e.g., due to formation of silanols by hydrolysis or due to irreversible adsorption of some admixtures from the sample or eluent may make the LC CAP irrepeatable. Pronounced peak broadening was observed in the critical adsorption area and this effect increased strongly with the polymer molar mass. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1363–1371, 1998     

Adsorption of monoclonal IgG on polystyrene microspheres

In this paper the adsorption of a monoclonal antibody IgG-1 isotype against HBsAg onto positively and negatively charged polystyrene beads has been studied. To determine the role played by electrostatic forces in the adsorption process different pH values were used. It was confirmed that the affinity of adsorption isotherms depends on the electrostatic interaction between protein and polymer surface. The maximum adsorption amount is located around the i.e.p. of the dissolved protein, and decreases markedly as pH moves away. Thus, the major driving force for adsorption of monoclonal antibodies on polystyrene beads comes from the hydrophobic interaction between the antibody molecules and the adsorbent surface. Desorption of preadsorbed IgG molecules by increasing ionic strength has shown that the positively charged polystyrene is also more hydrophobic in character than the negatively charged one. Finally, electrokinetic experiments have determined that the electric double layer (e.d.l.) of monoclonal antibody changes as the consequence of adsorbing on charged polymer surfaces.     

Liquid chromatography of polymers under limiting conditions of adsorption. IV. Sample recovery

The high performance liquid chromatography of polymers under limiting conditions of adsorption (LC LCA) separates macromolecules, either according to their chemical structure or physical architecture, while molar mass effect is suppressed. A polymer sample is injected into an adsorption-active column flushed with an adsorption promoting eluent. The sample solvent is a strong solvent which prevents sample adsorption. As a result, macromolecules of sample elute within the zone of their original solvent to be discriminated from other, non-adsorbing polymer species, which elute in the exclusion mode. LC LCA sample recovery has been studied in detail for poly (methyl methacrylate)s using a bare silica gel column and an eluent comprised toluene (adsorli) and tetrahydrofuran (desorli). Sample solvent was tetrahydrofuran. It was found that a large part of injected sample may be fully retained within the LC LCA columns. The amount of retained polymer increases with decreasing packing pore size and with higher sample molar masses and, likely, also with the column diameter. The extent of full retention of sample does not depend of sample volume. An additional portion of the injected desorli sample solvent (a tandem injection) does not fully eliminate full retention of the sample fraction and the reduced recovery associated with it. The injected sample is retained along the entire LC LCA column. The reduced sample recovery restricts applicability of many LC LCA systems to oligomers and to discrimination of the non-adsorbing minor macromolecular components of complex polymer mixtures from the adsorbing major component(s). The full retention of sample molecules within columns may also complicate the application of other liquid chromatographic methods, which combine entropic and enthalpic retention mechanisms for separation of macromolecules.     

Removal of dyes from water by conducting polymeric adsorbent

Chemically synthesized conducting polyaniline (PANI) was investigated as adsorbent for its possible application in the removal of organic dyes, such as methylene blue (MB) and procion red (PR) from their aqueous solution. PANI adsorbent behaves as a charged surface upon post‐synthesis treatment of the polymer with acid and base. The adsorbent thus treated shows a high selectivity for the removal of dyes in the adsorption process. The Langmuir adsorption isotherm was used to represent the experimental adsorption data. The cationic dye, MB can be preferentially removed by the base‐treated PANI while the anionic dye, PR is predominately removed by the acid‐treated one. These observations were further evidenced from the measurements of molar conductance and pH of the dye solutions employed for adsorption. The finding can be explained considering the electrostatic nature of adsorption coupled with the morphology of the PANI surface thus treated. Copyright © 2004 John Wiley & Sons, Ltd.     

基于金属有机框架水凝胶的一步式快速富集检测养殖水体中孔雀石绿北大核心CSCD

孔雀石绿是一种三苯甲烷类化合物,在水产品饲养中对疾病的防治有着不错的疗效,但因对人体健康有危害而被列为禁用药。由于实际样品中成分复杂,对于此类染料的检测方法难以同时兼具富集性好、灵敏度高且方便快速的优点。该工作制备了金属有机框架材料(MOF),采用MOF纳米材料掺杂的水凝胶(PAAM-SA/MOF)对养殖水体中的孔雀石绿进行吸附研究。采用一系列表征手段对MOF、PAAM-SA和PAAM-SA/MOF的微观形貌进行分析,结果表明吸附材料已成功合成。通过优化水凝胶吸附剂用量、吸附时间、孔雀石绿溶液pH、吸附温度、孔雀石绿溶液初始浓度等吸附萃取条件,使溶液中的孔雀石绿基本完全吸附在水凝胶中,在最优条件下,吸附效率最高可达97%。此外,采用不同极性的有机溶剂对吸附的孔雀石绿进行洗脱,通过优化洗脱液体积,脱附率最高达99%。在最佳条件下,该方法在高、中、低3个水平下的样品加标回收试验中回收率达到84.8%~118.1%,相对标准偏差小于5.1%,方法的检出限为0.083μg/L(S/N=3),定量限为0.25μg/L(S/N=10)。该方法简化了前处理过程,结合了MOF和水凝胶这二者各自的优点,添加的MOF材料可以在水凝胶体系中发挥其良好的吸附性,既解决了传统的MOF材料因粒径太小而回收率低的难题,便于吸附后直接提取,同时也解决了纯水凝胶吸附效率较低的问题,整体上提高了吸附效率和可回收性。实际样品测试表明该新型水凝胶吸附材料可用于养殖水体中孔雀石绿的快速萃取和检测,在食品检测领域具有很大潜力。     

Reconformation of polyvinylamine adsorbed on glass fibers

Surface area exclusion chromatography was used to investigate the reconformation of fully hydrolyzed polyvinylamine. The polymer is adsorbed on stacked glass fiber filters constituting the stationary phase while the polymer solution is injected at the inlet of the chromatography column. From numerical simulation and experimental chromatograms of nonreconforming polyelectrolytes, the amount of polymer adsorbed per filter represented as a function of the filter position along the column (the histogram) was determined to be continuously decreasing and not to depend on the rate of elution. For polyvinylamine, the histograms are peaked and the height of the peak was determined to depend greatly on the rate of polymer supply to the column that was controlled by monitoring the polymer concentration and/or the rate of elution (mass-transfer-controlled adsorption). Modifications in the adsorption on the successive filters were converted into changes in the interfacial area of adsorbed molecules taking into account model histograms as well as experimental adsorption histograms of non reconforming systems. Macromolecule concentration in the mobile phase and contact time between solute and adsorbed molecules were determined to be the two parameters controlling the extent of polymer desorption. The unusual shape of the histogram thus was attributed to reconformation of the adsorbed polymer, which was stimulated by interfacial exchange between segments belonging to trains of adsorbed macromolecules and chain segments of solute ones.     

Liquid chromatography of polymers under limiting conditions of adsorption: III. Role of experimental variables

LC of polymers under limiting conditions of adsorption (LC LCA) is a novel method based on different mobility of (pore excluded) macromolecules compared to (pore permeating) solvent molecules. Polymer sample is injected in a solvent preventing its adsorption within the column. Eluent promotes sample adsorption. Under these conditions, macromolecules cannot leave its initial solvent and elute from the column independently of their molar mass. In contrast, a less interactive simultaneously injected polymer leaves its initial solvent zone and is eluted in the size exclusion mode. As a result, chemically different polymer species can be discriminated. The effect of selected experimental conditions was studied on the LC LCA behavior of poly(methyl methacrylate)s eluted from bare silica gel columns. The parameters were packing pore diameter, injected sample volume and concentration, as well as column temperature. The size independent elution was only little affected by the above parameters and LC LCA produced well-focused peaks. The LC LCA mechanism was operative even at a very large sample of both volume and concentration. This makes LC LCA a robust and user-friendly method, likely suitable also for characterization of minor components of polymer mixtures.     

螺吡喃功能化UiO-66光响应吸附剂的制备及其性能

将光响应分子甲基螺吡喃SP-CH₃引入UiO-66的非极性孔笼中,构筑吸附活性位可光控调节的光响应吸附剂。SP-CH₃功能化的吸附剂完好保留了载体UiO-66的骨架和孔道结构。以阴离子染料甲基橙为探针,研究了吸附剂在不同光照条件下的吸附和解吸性能。结果表明,经紫外光照后,吸附剂对甲基橙的吸附量为41.99 mg·g^-1,相较于可见光照后样品的吸附量提升57.56%,吸附作用增强;经可见光照后,甲基橙的脱附量为81.6%。本策略通过光照刺激改变UiO-66孔笼中SP-CH₃的构型及表面电荷性质,即对吸附活性位进行光控调节,在不同光照条件下实现对吸附质的高效吸附和有效脱附。     

螺吡喃功能化UiO-66光响应吸附剂的制备及其性能

将光响应分子甲基螺吡喃SP-CH₃引入UiO-66的非极性孔笼中,构筑吸附活性位可光控调节的光响应吸附剂。SP-CH₃功能化的吸附剂完好保留了载体UiO-66的骨架和孔道结构。以阴离子染料甲基橙为探针,研究了吸附剂在不同光照条件下的吸附和解吸性能。结果表明,经紫外光照后,吸附剂对甲基橙的吸附量为41.99 mg·g^-1,相较于可见光照后样品的吸附量提升57.56%,吸附作用增强;经可见光照后,甲基橙的脱附量为81.6%。本策略通过光照刺激改变UiO-66孔笼中SP-CH₃的构型及表面电荷性质,即对吸附活性位进行光控调节,在不同光照条件下实现对吸附质的高效吸附和有效脱附。