Sulfonated and Ordered Mesoporous Polymers for Reversible Adsorption of Ammonia: Elucidation of Sequential Pore-Space Diffusion

NH 3 adsorption and separation are pivotal for its safety and e�cient utilization, but most solid adsorbents show either low capacity or unsatis�ed separation performance. Herein, we report sulfonated and ordered mesoporous polymers (SOMPs) synthesized from solvent-free manual-grinding of resorcinol and 1,4-phthalaldehyde with copolymer template, curing at 140~220°C, simultaneous sulfonation and template removal by treating with H 2 SO 4 . The prepared SOMPs possess ordered mesopores with abundant microporosity, large surface areas (~697 m 2 /g), and extremely-high –SO 3 H densities (~4.48 mmol/g). Their NH 3 capacities are as high as 15.09 mmol/g (25°C, 1.0 bar), exhibiting NH 3 breakthrough time and saturated capacity up to 138 min/g and 6.16 mmol/g, respectively (5.0v%NH 3 /23.75v%N 2 /71.25v%H 2 ). Versatile characterizations together with molecular dynamics simulations demonstrate the superior NH 3 adsorption performance originates from strong a�nity of – SO 3 H group with NH 3 in sequential pore-space of SOMPs, which not only enhances the molecular recognition ability, but also effectively promotes NH 3 fast diffusion inside SOMPs.


Introduction
Ammonia (NH 3 ) has constituted the basement for the development of modern agriculture, since it is the essential feedstock for synthesizing various nitrogen fertilizers. 1,2NH 3 is also proposed as the safe medium for storage and transportation of H 2 due to its large hydrogen density (11.8 wt.%) and relatively easy liquidation (b.p. −33.5 ℃). 3 The throughput of NH 3 has reached as high as ~200 million tons per year across the world. 4However, the effective separation and puri cation of NH 3 from the NH 3 synthesis process is still a challenge, and imposes signi cant energy consumption on the whole process.On the other hand, the utilization of NH 3 inevitably leaves a trace of NH 3 in the tail gas of industrial process, which will cause severely environmental issues and signi cant threats to human health. 5Therefore, effective separation and recycling of NH 3 is highly demanded during its synthesis and application in the industry.
To tackle mentioned problems, many materials have been engineered for the selective and reversible capture of NH 3 .For example, ionic liquids (ILs) 6-10 and deep eutectic solvents (DESs) [11][12][13][14][15] with extremely low volatility and tunable properties were investigated for NH 3 absorption.However, the liquid absorption requires continuous transportation of liquid absorbents in the pipelines and towers during the gas absorption process, and the high viscosity of ILs and DESs interferes their practical applications.
Alternatively, zeolites, 16 activated carbons, 17 metal-organic frameworks (MOFs), 5,18 and porous organic polymers (POPs) 19 with permanent nanoporosity and tailorable frameworks are promising candidates for NH 3 adsorption.These solid adsorbents are normally xed into two parallel towers, and operated successively for adsorption and desorption, thus avoiding the transportation issues associated with liquid absorbents.In addition, the solid adsorption features low energy consumption, free from corrosion, and low investment for the facilities in relative to the liquid absorption.
Regarding the solid adsorption for selective and reversible capture of NH 3 , previous works mainly focused on construction of abundant micropores with tunable diameter to improve the physical adsorption of NH 3 , 20,21 and incorporation of active sites with proper a nity to improve the chemical adsorption of NH 3 . 22,23Although micropores are favorable for the condensation of NH 3 due to the capillary effect, the lling capacity of micropores are limited by their low volumes.To date, there are scarce studies noting the importance of mesopores with enhanced pore volumes in the selective adsorption of NH 3 .Particularly, the mesopores with uniform size and long-range orderings can provide not only enlarged space for NH 3 lling, but also the barrier-eliminated channels for NH 3 diffusion.
The actives sites for the chemical adsorption of NH 3 mainly include open metal centers [23][24][25] and acidic groups. 26,27The former ones enable multiple coordination interaction with NH 3 , and the latter ones enhance acid-base interaction with NH 3 .][30][31] It will be very fascinating if the functional materials for NH 3 reversible capture can be synthesized through a sustainable and cost-effective route.
Herein, we report a successful synthesis of highly sulfonated and ordered mesoporous polymers (SOMPs) through a solvent-free self-assembly route.As illustrated in Scheme 1, resorcinol and 1,4phthalaldehyde monomers together with triblock copolymer template were mixed thoroughly by manual grinding at room temperature, followed by curing at 140~220 ℃ to result in pristine ordered hexagonal mesoporous polymers (OMPs), 32,33 which were then treated with concentrated H 2 SO 4 to simultaneously realize high-degree sulfonation and template removal (see Experimental Section for the detailed synthetic procedures).It was found that the synthesized SOMPs enable remarkable adsorption of NH 3 , with the capacities of 11.53~15.09mmol/g for pure NH 3 at 25 ℃ and 1 bar, and as high as 6.16 mmol/g for 5 vol.% of NH 3 at 25 ℃.The adsorption of NH 3 on the SOMPs is also highly selective to those of N 2 and H 2 , and totally reversible without loss of NH 3 capacities after 30th recycling.With the assistance of multiple characterizations and molecular dynamics simulations, it is revealled that the NH 3 molecules prefer to be adsorbed in micropores at low loadings, and then in mesopores at medium to high loadings.This is for the rst time that the sequential pore-space diffusion of NH 3 , and the importance of mesopores in the selective adsorption of NH 3 were systematically elucidated.

Results And Discussion
The synthesized SOMPs were denoted as OMP-SO 3 H-x, where x stands for curing temperature.The porous structure of the synthesized SOMPs was characterized by XRD, N 2 sorption and electron microscopy, as given in Figure 1. Figure 1a shows small-angle XRD patterns of various SOMPs, which display three well-resolved diffraction peaks at around 0.88°, 1.52° and 1.76°.These peaks can be indexed to (100), ( 110) and (200) re ections, suggesting the formation of ordered mesostructure with two-dimensional (2-D) hexagonal symmetry (p6mm) in these samples.However, wide-angle XRD patterns of the SOMPs display only two weak peaks at 17.8° and 42.5° (see Figure S1), suggesting their noncrystalline networks.Figure 1b shows N 2 adsorption-desorption isotherms at −196°C of the SOMPs, which display type IV pro les with H1 hysteresis loops.Such N 2 sorption isotherms indicate the presence of ordered hexagonal mesopores with abundant micropores in the SOMPs.The ordered hexagonal mesopores are undoubtedly formed by the oriented assembly of polymer precursors with F127 micelles. 34,35The micropores are originated from the embedding of some F127 chains in the mesopore walls, 36,37 and the removal of which leaves the voids with sub-nanometer size.Figure 1c shows pore size distributions of the SOMPs, which display trimodal pro les with the pore size of 0.63~0.73,1.17~1.35and 6.34~13.60nm.The textural parameters of the SOMPs calculated from the N 2 adsorption data are summarized in Table 1.It can be seen that the surface areas, micropore volumes and total pore volumes of the SOMPs rstly increase but then decrease with the increase of curing temperatures.Thus, the OMP-SO 3 H-180 exhibits the highest porosity among the SOMPs.However, the pore size of the SOMPs gradually increase with curing temperatures.Thus, the OMP-SO 3 H-220 exhibits the largest pore size among these SOMPs.According to the elemental analysis, the sulfur contents of the SOMPs are 8.96~14.36wt.% (Table 1 and  S1), corresponding to −SO 3 H densities of 2.80~4.48mmol/g.Such concentration of the −SO 3 H group supports the enhanced sulfonation degree of the SOMPs, much higher than those of the sulfonated materials reported yet.It is also noted that the sulfur contents of the SOMPs decrease with the increase of curing temperatures.This might be a result of the more rigid structure of the SOMPs as the curing temperatures increase, so that the −SO 3 H group became more di cult to be grafted onto the frameworks.
Meanwhile, the H + capacity of the SOMPs were up to 4.4 mmol/g, which is a record value among the sulfonated porous solid acids yet.
The chemical structures of the SOMPs were characterized by solid-state NMR, XPS spectra, as shown in groups (150 and 141 ppm), and terminal -CH 3 and −CHO groups attached to benzene rings. 28To study the intrinsic acidity of the SOMPs, reliable and classical 31 P solid-state NMR combining TMPO probe molecule were carried out (see Figure 2b).It can be seen a pronounced and symmetric peak at ~79 ppm, which were ascribed to TMPO adsorbed on the strong acidic −SO 3 H site with uniform distribution. 44High acid density combined with strong and uniform acid strength play crucial roles for their applications in selective capture of alkaline gas such as NH 3 .Figures 2c~d, Figure  40,41 The O1s spectra can be deconvoluted into two peaks at 531.4 and 532.9 eV, ascribing to O−S bond and O−C/O−H bonds. 42The S2p spectra can be deconvoluted into two peaks at 166.5 and 167.8 eV, ascribing to S−C bond and S−O bond. 26,43All these results con rm successful grafting of −SO 3 H group onto OMPs' framework.
As a result, given the high acid density with suitable acid strength, artistic microporosity tandem ordered mesoporosity, the SOMPs are expected to have great potential application in the separation of NH 3 .The performance of the SOMPs for NH 3 selective adsorption was rstly examined, as depicted in Figure 3. capacities than those of the other SOMPs (see Figure S9).Therefore, the strong interaction of SOMPs with NH 3 is originated from the acid-base a nity between grafted −SO 3 H and NH 3 molecules, while −OH group with weak acidity in the SOMPs play relatively low role for the adsorption of NH 3 .It is noted that NH 3 capacities of the SOMPs rstly increase but then decrease with curing temperatures.Thus, the OMP-SO 3 H-180 exhibits the highest NH 3 capacities among the SOMPs.This is well consistent with the variation of porosity for the SOMPs with curing temperatures.Additionally, the NH 3 capacities of the SOMPs decrease with the increase of temperatures, suggesting the exothermic nature of NH 3 adsorption process.The isosteric heats of NH 3 adsorption by OMP-SO 3 H-180 and OMP-SO 3 H-200 were calculated by the Clausius-Clapeyron equation, distributing in the range of −65 ~ −45 kJ/mol (Figure S10). 12,19The magnitude of NH 3 adsorption heats agree well with the non-ideal adsorption of NH 3 by the SOMPs.
Overall, the NH 3 capacities of the SOMPs are very high, with the value of 15.09 mmol/g for the OMP-SO 3 H-180 at 25°C and 1 bar, which is quite competitive in relative to those of other solid adsorbents reported in the literature (Table S2).Owing to the non-ideal adsorption of NH 3 by SOMPs, the NH 3 capacities of them at low pressures are even more signi cant.For example, the OMP-SO 3 H-180 can adsorb 6.6 mmol/g of NH 3 at 25°C and 0.05 bar, being superior to most other solid adsorbents reported in the literature (Table S2).This result is particularly important, because the contents of NH 3 in industrial gas are normally low, and the performance of solid adsorbents for adsorption of NH 3 at low pressures is more concerned. 45,46r the separation of NH 3 , the most important task is to selectively adsorb NH 3 from N 2 and H 2 mixture.
Previous works have illustrated that the adsorption of inert gases on mesopore walls is much weaker than that on micropore walls due to the reduced capillary condensation effect. 28,47However, the adsorption of acidic gases over mesoporous adsorbents can be well maintained by grafting basic sites onto the mesopore walls.Thus, highly e cient and selective adsorption of acidic gases from inert gases can be realized by constructing abundant mesopores and grafting suitable basic sties in solid adsorbents.It is deduced that similar principles can also be applied for selective separation of NH respectively.The values agree well with the NH 3 capacities at 0.05 bar calculated from the NH 3 isotherms (6.28 and 5.03 mmol/g).More importantly, the above penetrated parameters of OMP-SO 3 H-180 are very well maintained even after being treated saturated water vapor at 50°C for 2 h, suggesting the excellent water resistance of SOMPs for NH 3 adsorption (Figure S13).These results con rm that the SOMPs can be used as highly e cient and selective adsorbents for NH 3 from N 2 and H 2 , much better than variously reported adsorbents in the eld. 26,50,51e adsorption/desorption behavior of NH 3 on the SOMPs was then examined, as shown in Figure 4.
Figure 4a shows recycling of the OMP-SO 3 H-180 for NH 3 adsorption at 25°C and 1.0 bar, while desorption was performed at 150°C and 0.001 bar.Noting that the SOMPs are stable enough at such desorption temperature (Figure S14).It can be seen that the NH 3 capacity of the OMP-SO 3 H-180 remains almost unchanged after 30th cycling, giving the attenuation ratio only 1.6%.In contrast, the attenuation ratio on NH 3 capacity over MOFs adsorbents (e.g.Ce-MOF) was as high as 39.1% under identical condition (Figure S15).Therefore, the adsorption of NH 3 on the SOMPs is totally reversible and quite durable.
Figure 4b shows in-situ DRIFTS spectra of the OMP-SO 3 H-180 with 0.05 vol.% of NH 3 purge at 25°C.As exposure time prolongs, four characteristic peaks associated with chemically adsorbed NH 3 gradually appear with increased intensities.For instance, the characteristic bands (1720, 1539, and 1265 cm −1 ) correspond to the asymmetric, and symmetric bending vibrations of NH 4 + , and the band at 1450 cm −1 is assigned to NH 3 interacts with -SO 3 H group. 52,53 Figure 4c shows NH 3 -TPD MS curve of the OMP-SO 3 H-180, exhibiting two NH 3 desorption peaks centered at around 113°C and 188°C.Considering the uniform acid strength of the sample determined by 31 P solid-state NMR spectra, two desorption peaks should be resulted from the -SO 3 H located in different microenvironment of micropores and ordered mesopores.
Similar phenomenon can also be con rmed by controlling NH 3 adsorption behavior, as given in Figure 4d.
Notably, the fresh OMP-SO 3 H-180 has two adsorption steps distributed at 0~0.1 bar and 0.1~1.0bar, which show quadratic function and linear function characteristics respectively.The former was resulted from NH 3 interacts with -SO 3 H in micropores due to capillary condensation effect, the latter was resulted from NH 3 interacts with -SO 3 H in mesopores.After saturated adsorption, controllable desorption of NH 3 in mesopores was performed by treating the sample at suitable temperature (see experimental section for the mesoporous adsorption measurements).The NH 3 isotherm of the degassed sample shows only linear function characteristic, which is consistent with the NH 3 isotherm in mesoporous adsorption part of the fresh OMP-SO 3 H-180.The result con rms novel sequential pore-space diffusion rule of NH 3 in interconnected micropores and ordered mesopores, the diagrammatic sketch was depicted in Figure S16.As a result, the SOMPs show a record integrated performance in selective adsorption and separation of NH 3 , far better than the industrial H-ZSM-5 zeolite with pure micropores and sulfonated mesopores silica of SBA-15-SO 3 H (Figure S17, and Table S3).
Based on the above statement, the sequential pore-space diffusion in interconnected micropores and ordered mesopores plays a key role for their excellent integrated performance in NH 3 selective capture and separation.To better understand the inherent diffusion rule of NH 3 , molecular dynamics simulations were performed as a complement to the experimental approaches, which can re ect the adsorption and diffusion dynamical process of NH 3 in the SOMPs on theoretical level.Figure S18 shows the simulated frameworks of the OMP-SO 3 H-160 and OMP-SO 3 H-180 possess both microporous and mesoporous channels.The two best SOMPs with excellent NH 3 adsorption performance.Noting that OMP-SO 3 H-180 owns more micropores while OMP-SO 3 H-160 owns more mesopores because of their density difference.
Then the adsorption and diffusion of NH 3 molecules in the two SOMPs were studied.Figure 5 shows the snapshot of NH 3 molecules adsorption and diffusion trajectory of one representative NH 3 molecule in the OMP-SO 3 H-180 at low, medium and high loadings.At low loading, due to the strong acid-base interaction between −SO 3 H group and NH 3 molecule as well as the con nement effect of micropores, most of the NH 3 molecules are adsorbed strongly (Figure 5a) and migrated slowly in the microporous channels (Figure 5d).At medium loading, some NH 3 molecules transport from microporous channels to mesoporous channels, and part of NH 3 molecules located in mesopores due to the micropores have already been completely occupied (Figure 5b and 5e).While at high loading, more NH 3 molecules permeate into the mesoporous channels (Figure 5c and 5f).Meanwhile, the diffusion behavior could also be quantitatively analyzed by diffusion radius, 54 and the rapid movement is generally accompanied by large diffusion radius (R d ).At low loading, as most of NH 3 molecules hop between multiple −SO 3 H groups in microporous channel, R d is small as well as diffusion is slow (Figure 5g).Interestingly, with the increase of loading, R d is dramatically increased, and more NH 3 molecules could diffuse from microporous to mesoporous channels (Figure 5h and 5i).The same adsorption and diffusion behavior of NH 3 molecules can also be observed in OMP-SO 3 H-160 (Figure S19).Overall, sequential pore-space adsorption and diffusion mechanism of NH 3 molecules inside microporous and mesoporous channels of the SOMPs has been illustrated, in which micropores preferential adsorption together with ordered mesopore subsequent storage of NH 3 , thus maximally utilizing the volume advantage of micro-and mesoporosity for NH 3 selective capture.Overall, the OMP-SO 3 H-x show much better performance than industrial zeolites applied in NH 3 selective adsorption and separation, offering great opportunities for their wide applications in the eld.Although the NH 3 capacity of the OMP-SO 3 H-x was a little lower than few special MOFs adsorbents, but their low cost, easy preparation, and good corrosion resistance are very favorable for their scalable usage in the industry.

Conclusion
In summary, a class of stable and ordered mesoporous polymers functionalized with ample sulfonic groups were successfully developed by using the scalable and sustainable solvent-free route.The obtained SOMPs have record-high sulfonation degree (4.48 mmol/g), large BET surface areas (697 m 2 /g), highly ordered hexagonal mesopores combined abundantly interconnected micropores, thus possessing advantages of ideal solid adsorbents for alkaline gas capture.As expected, the SOMPs show the record integrated performance in selective adsorption and separation of NH 3 , much higher than those of variously porous solid adsorbents reported previously.The novel inherent mechanism on sequential pore-space diffusion of NH 3 were also proposed based on both experimental results and molecular dynamics simulations.This work ignites research interest on the importance of ordered mesopores interconnected abundant micropores for corrosive gas selective capture and separation, and offers great opportunities for scalable preparation of high-capacity and low-cost porous adsorbents in the industry.

Chemicals and reagents
Resorcinol (99 wt.%), Synthesis of SOMPs 0.44 g of resorcinol, 0.56 g of 1,4-Phthalaldehyde and 2.0 g of F127 were manually ground to achieve a uniform mixture within 5 min.The mixture was transferred to a small Te on beaker (20 ml) and heated at 140, 160, 180, 200 or 220°C for 24 h, and reddish-brown solidi ed product was obtained.Then, the solidi ed product was dispersed in 100 mL of sulfuric acid (80 wt.%) under stirring at 80°C for 24 h, and this step was repeated for the second time.Finally, the resultant solid was ltered and washed thoroughly with hot anhydrous ethanol, and dried under vacuum at 100°C overnight.For comparison, SBA-15-SO 3 H and Ce-MOF were prepared as the literatures. 55,56struments for characterizations X-ray diffraction (XRD) patterns were obtained on an X'Pert3 Powder diffractometer using Cu Kα radiation (λ = 1.5418Å, V = 45 kV and I = 40 mA) at a scanning rate of 1°/min.The N 2 adsorption-desorption isotherms at −196 ℃ were measured on a Micromeritics TriStar II 3020 analyzer, and the samples were degassed under vacuum at 150°C for 6 h prior to measurements.The surface areas were calculated using the adsorption data in the relative pressure range of 0.05~0.30according to the Brunauer-Emmet-Teller (BET) equation.The pore size distributions were calculated using the density functional theory (DFT) method, and the micropore volumes and total pore volumes were also calculated using the same method.The scanning electron microscopy (SEM) images were obtained on a Hitachi S-4800 microscope at an acceleration voltage of 5 kV.The transmission electron microscopy (TEM) images and energydispersive X-ray (EDX) spectroscopy elemental mapping analysis were obtained on a JEOL JEM-2010 electron microscope.The Fourier transform infrared (FT-IR) spectra were obtained on a Nicolet iS50 spectrometer.Elemental analysis (EA) was carried out on a Vario EL III elemental analyzer.The In-situ diffused re ectance infrared Fourier transform spectroscopy (DRIFTS) spectra were obtained on a Nicolet iS50 spectrometer equipped with an in-situ diffuse re ection cell.The spectra were collected with a resolution of 4 cm -1 and scanning of 64 cycles.The sample was pretreated by owing N 2 at 120°C for 1 h before each experiment.During the adsorption process, 0.05 vol.% of NH 3 balanced in N 2 was purged into the in-situ diffuse re ection cell at 30°C and the signal was recorded at different times.The NH 3temperature programmed desorption (TPD) curves were measured on a Micromeritics AutoChem II 2920 analyzer connected to a Hiden HPR-20 R&D mass spectrometer.First, ~100 mg of sample was purged with He at 150°C for 2 h to remove physically adsorbed water.Then, the sample was cooled to 50°C and dosed for 30 min with 5 vol.% of NH 3 balanced in He.After being purged by He gas to eliminate the physically adsorbed NH 3 , the sample was heated to 350°C at 10°C/min, under He ow of 30 mL/min.The tail gas was analyzed online by the mass spectrometer.

Gas adsorption measurements
Prior to measurements, the samples were degassed under vacuum at 150°C for 6 h.The NH 3 adsorption isotherms were measured using a self-made equipment, the accuracy of which has been validated in our previous work. 26,57,58The equipment is mainly composed of two stainless steel chambers connected to two pressure transducers, respectively.The amounts of NH 3 adsorbed can be calculated according to the changes of the pressures in two chambers after the samples getting in contact with NH 3 .The diagram for the equipment and detailed measuring procedures are presented in the Supporting Information (see Scheme S1 and related description).The N 2 and H 2 adsorption isotherms at 25°C were measured on a Micromeritics TriStar II 3020 analyzer mentioned above.
Breakthrough curves for NH 3 /N 2 /H 2 mixed gas adsorption were measured on a Micromeritics AutoChem II 2920 analyzer connected to a Hiden HPR-20 R&D mass spectrometer.All the measurements were conducted using a U-type quartz tube (6 mm inner diameter × 190 mm length).In a typical run, a certain amount of sample (~100 mg) was xed in the quartz tube; the sample was rst purged with He ow (30 mL/min) at 150 ℃ for 3 h to remove any volatile residues; the temperature was then cooled down to the target temperature of 25 or 50 ℃, and the He ow was switched to 5v%NH 3 /23.75v%N 2 /71.25v%H 2 mixed gas ow (20 mL/min) for competitive adsorption.The composition of inlet gas was controlled by mass owmeters.The compositions of outlet gas were measured online by the mass spectrometer.To evaluate the water resistance of OMP-SO 3 H-180, the sample was rstly treated with saturated water vapor at 50°C for 2 h, which was then performed the above breakthrough test.

Figure
Figure 1d and Figure S2 show SEM images of the OMP-SO 3 H-180, exhibiting ample cavities with wellordered features, which are similar to those in other SOMPs (Figures S3~S4).Meanwhile, TEM images of the sample show highly ordered mesopores viewed from (110) direction associated with 2-D hexagonal symmetry (p6mm) and open cylinder shape can be clearly observed in the OMP-SO 3 H-180 (Figure 1e).In addition to the ordered mesopores, starry worm-like holes with sub-nanometer size can be clearly observed in the sample, suggesting they were also rich in microporosity.Figures 1f~i show STEM image with elemental mapping of the OMP-SO 3 H-180.It can be seen that C, O and S atoms are uniformly

Figure 2 .
In comparison with non-sulfonated OMP, the FT-IR spectra of SOMPs displayed additional four characteristic peaks at around 1016, 1040, 1125 and 1171 cm −1 , which are ascribed to the signals of −SO 3 H groups38,39 (FigureS5and FigureS6).Figure2ashows13 C solid-state NMR spectra of the SOMPs, displaying a series of peaks associated with the carbon atoms in different environments, which include the −CH 2 − bridges between benzene rings (20.1 and 40.1 ppm), aromatic carbon atoms without being attached by heteroatoms (128 ppm), aromatic carbon atoms attached by −OH and −O−SO 3 H S7 and Figure S8 show XPS spectra of the SOMPs.The C1s spectra can be deconvoluted into three peaks at 284.4, 285.3 and 286.1 eV, ascribing to C−C/C−H bonds, C−S bond and C−O bond respectively.

Figures
Figures 3a~b show theNH 3 sorption isotherms of the SOMPs at 25 and 50°C, which give obviously nonideal pro les, indicating the strong interaction of the SOMPs with NH 3 .However, the NH 3 adsorption isotherm of non-sulfonated sample OMP-180 exhibits an almost ideal pro le, with much lower NH 3

Table 1
Textural parameters and sulfur contents of the SOMPs.
3fr49 N 2 and H 2 .Since the SOMPs have abundant mesopores and micropores as well as high −SO 3 H density, it is anticipated that the adsorption of inert gases N 2 and H 2 by them is much lower than that of basic gas NH 3 .As expected, the N 2 and H 2 adsorption isotherms of the SOMPs at 25°C (FigureS11~S12) display almost ideal pro les with the N 2 and H 2 capacities being about two magnitudes lower than the NH 3 capacities.Figures 3c~d shows the selectivities of the SOMPs for NH 3 /N 2 and NH 3 /H 2 at 25°C and 1 bar, obtaining from ideal adsorption solution theory.48,49Itcan be seen that when the molar fraction of NH 3 in gas phase is 0.05, the IAST selectivities of NH 3 /N 2 and NH 3 /H 2 for the OMP-SO 3 H-180 reach 453 and 1768.Figures 3e~f show the breakthrough curves for NH 3 /N 2 /H 2 mixed gas over the OMP-SO 3 H-180 at 25 and 50°C.It can be seen that N 2 and H 2 instantly penetrate the xed bed, indicating negligible adsorption of the two gases.Interestingly, the penetration of NH 3 starts at ~138 min/g and completes at ~263 min/g at 25°C.Similarly, the penetration of NH 3 still starts at ~124 min/g and completes at ~255 min/g at 50°C.The accelerated penetration of NH 3 is ascribed to the decreased NH 3 capacities as the temperatures increase.By integrating the breakthrough curves, it is estimated that the OMP-SO 3 H-180 can adsorb 6.16 and 5.53 mmol/g of NH 3 from NH 3 /N 2 /H 2 (5/23.75/71.25 vol.) mixture at 25 and 50°C, 1,4-phthalaldehyde (98 wt.%) and Pluronic F127 (M n =13000) were purchased from Macklin Chemical Reagents Co. Ltd., China.NH 3 (99.99vol.%),N 2 (99.99 vol.%) and H 2 (99.99 vol.%) were purchased from Dalian Special Gas Co. Ltd., China.All the chemicals were directly without further puri cation.H form ZSM-5 zeolite was supplied by Sinopec Co. Ltd.
Larmor frequency of 202.63 MHz, and a 4 mm magic-angle-spinning (MAS) probe operated at a spinning rate of 12 kHz was used.The X-ray photoelectron spectroscopy (XPS) spectra were obtained on a Thermo ESCALAB 250XI spectrometer, and the C 1s peak at 284.8 eV was used as the standard for calibrations.The thermogravimetric analysis (TGA) curves were measured on a Netzsch STA2500 Regulus TG/DTA analyzer by heating the samples from room temperature to 850°C at a ramping rate of 10°C/min under the owing N 2 .
13C solidstate nuclear magnetic resonance (NMR) spectra were collected on a Varian Inova 400 MHz spectrometer.The 31 P solid-state NMR spectra were obtained on a Bruker Avance III 500 MHz spectrometer at a