Pore Space Partition in Rigid Metal-Organic Frameworks Containing Organic Vertices for Trace Benzene Adsorption

Pore Space Partition in Rigid Metal-Organic Frameworks Containing Organic Vertices for Trace Benzene Adsorption | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Pore Space Partition in Rigid Metal-Organic Frameworks Containing Organic Vertices for Trace Benzene Adsorption Huajun Yang, Yingying Zhang, Chaozhuang Xue, Zhi Fang, Yexin Huang, and 6 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4530984/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted You are reading this latest preprint version Abstract The physical adsorbents have shown great promise for the removal of volatile organic compounds (VOCs) such as benzene but they still suffer from low uptake and poor selectivity especially when VOCs are present at trace concentrations. In this work, we demonstrate the successful implementation of pore-space-partition ( PSP ) strategy on rigid NU-1500-type metal-organic frameworks (MOFs) containing organic vertices, which has led to a series of MOFs with near-organic backbones (metal mass fraction as low as 5%) and record trace benzene adsorption. The PSP on rigid acs MOFs here relies on precise size match and symmetry match between the partitioning ligands and the frameworks. NNM-750-Fe, a structure constructed by partitioning NU-1500 with large π-conjugated hexaazaphenalene-based ligand, exhibits significantly enhanced low-pressure benzene capture than NU-1500-Fe, which far exceeds previous records (42%-69% higher) at a wide pressure range (P/P 0 from 0.003 to 0.01). DFT calculations reveal that the hexaazaphenalene core has a higher benzene affinity than the open metal sites in pristine NU-1500. Physical sciences/Chemistry/Coordination chemistry Physical sciences/Engineering/Chemical engineering Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Introduction Metal-organic frameworks (MOFs) are built by connecting metal-containing secondary building units (SBUs) with organic ligands 1 . In general, the inorganic SBUs is treated as vertex and the organic ligands is treated as linkers in simplifying the MOF structures 2-6 . However, the high-connected organic linkers have made the line between such structural roles of inorganic components and organic components blurred and sometimes the roles were even reversed 7-9 . For example, MOF-688 had a dia topology with 4-connected tetrahedral tetrakis(4-formylphenyl)methane organic building units as vertices and 2-connected polyoxometalate cluster as linkers 10 . Compared to MOFs built on inorganic vertices, a potential advantage of MOFs with part or all organic vertices is the lightweight framework, which is beneficial for high guest uptake in adsorption applications. An excellent example is the series of NU-1500 structures with an acs topology, which is built on trivalent trinuclear metal (Fe 3+ , Cr 3+ , Al 3+ and Sc 3+ ) clusters and trigonal prismatic ligands 11,12 . A main difference of NU-1500 from prototypical acs (MOF-235/MIL-88) is half of the 6-connected inorganic node is substituted by 6-connected organic vertices, resulting a rigid framework 13-15 . NU-1500-Cr showed an impressive water uptake and NU-1501-Al with high porosity and surface area yielded a methane storage capacity over U.S. Department of Energy target 11,12 . With the lightweight frameworks, however, the pore size of NU-1500 structures is too large to enable a strong host-guest interaction to confine the small molecules for adsorption/separation applications at ambient conditions. Pore-space-partition ( PSP ) strategy, which refers to the division of large pores into small segments, is a fruitful approach to increase the density of binding sites and has achieved great experimental success 16-20 . Of potential relevance to NU-1500 structures is that PSP has been proved to be incredibly successful in acs topology by introducing a symmetry-matched pore-partitioning agent into the flexible acs framework 13,14 . The partitioned acs ( pacs ) platform rank among the best MOFs in a range of properties such as high gas up-take and high chemical stability 21 . We are thus intrigued by the prospect that the implementation of PSP on lightweight NU-1500 structures may set new adsorption record. The aromatic guest would be of particular interest due to introduction of π-conjugated partitioning ligand. The application of the PSP strategy on NU-1500 frameworks faces an extra hurdle because the directional nature of covalent bond in organic vertex has led to a rigid acs framework (Fig. 1) 11 . This is different from the case in previously reported flexible acs phases based on ditopic carboxylate ligands. Due to the nondirectional nature of metal-carboxylate bonds, they showed large size tolerance toward pore-partitioning agent 20 . As a consequence, in addition to symmetry match, strict size match between the partitioning agent and the framework is required for PSP on NU-1500 frameworks. With the above considerations in mind, in this work, we were able to make eight MOFs with four ligand pairs and two trivalent metals (Fe 3+ , Cr 3+ ). The NNM MOFs (NNM stands for Nanjing Normal University Materials) reported here integrated ultralow metal density, high porosity, and high structural stability. Cr based NNMs show ultrastability which can withstand extreme pH conditions from concentrated hydrochloric acid to 1 M NaOH solution. NNMs with high porosity exhibit top-level adsorption performance toward volatile organic compound of benzene due to the introduction of conjugated partitioning ligand. Especially for NNM-750 structures, which show record capture capacity at ambient temperature and a wide range of relative pressure. PSP on rigid acs and structural analysis. A main issue for PSP in NU-1500 frameworks based on the trigonal prismatic linkers is the rigidity of the framework inherited from rigid organic nodes. A closer look at the structure showed that the motion of metal carboxylate bond at the cluster is restricted by the directional C-C bonding at the linkers, leading to a rigid acs framework (Fig. 1). As such, the implementation of PSP strategy here requires an extra size match between the partitioning ligand ( P ) and trigonal prismatic ligand ( L ) in addition to symmetry match in prototypical flexible acs . (Supplementary Fig. 1). Based on the geometry of the framework, a linear equation was derived to determine the relation between the size of trigonal prismatic linkers and the partitioning ligands. d L is defined as the length of L projected onto c plane where the length of L is the length from the center of L to the center of two terminal carboxylate oxygens. The P -related size ( d P ) is the distance from the center to terminal nitrogen atom on pyridine. The relation between d L and d P is finally determined to be d P = d L – 1.8 Å (Supplementary Fig. 2). It could be deduced that four pairs of ligands match well for the implementation of PSP strategy (L1-P1 for NNM-750, L2-P2 for NNM-751, L2-P3 for NNM-752, and L3-P1 for NNM-753, Fig. 2a and Supplementary Fig. 3). The crystal size of all the Fe MOFs were suitable for single crystal X-ray diffraction (SCXRD) measurement (Supplementary Fig. 4). The detailed crystallographic information is shown in Supplementary Table 1-4. The experimental PXRD patterns of Fe phases matched well with simulated ones from single-crystal data, suggesting the phase purity of as-synthesized samples (Supplementary Fig. 5). SCXRD analysis suggests that the NNMs have lower symmetry compared with their parent structures. In particular, the partitioned NU-1500 (NNM-750) has a lowest space group of P 3, in comparison with P -6 m 2 of NU-1500. Detailed structural analysis shows that the distances from 6- c ligand to the trimers in NNM-750 are not consistent, with three shorter ones on one side and three longer ones on the other (Supplementary Fig. 6). Such a distortion is probably due to the subtle size mismatch between the framework and the ligands. The extra-framework volume for the NNMs were calculated to be 66.0 % (NNM-750), 77.1 % (NNM-751), 76.9 % (NNM-752) and 70.8 % (NNM-753) by using PLATON program, lower than their corresponding nonpartitioned structures due to the insertion of P ligands. An evidence for the size match is that the unit cells have remained essentially unchanged after PSP . For example, the a -axis for NU-1500-Fe and NU-1501-Fe are 19.57 Å and 24.96 Å, while for PSP resulted NNM-750-Fe and NNM-751-Fe are 19.31 Å and 24.69 Å respectively, with the size difference smaller than 3 percent (Supplementary Fig. 7). The deviation is attributed to slight bending of the long branch of L ligands, and the size tolerance for partitioning ligand is expected to marginally increase with the length of the branch. Further controlled experiments were carried out to certify the rigorous size match for PSP. We have tried to use tripyridyl ligands with different size to partition the rigid NU-1500 and NU-1501, e.g., smaller P ligand of tpt ( d P = 5.55 Å) or bigger P ligand of tpbtc ( d P = 7.88 Å) to partition NU-1500; a slight bigger P of tpapa ( d P = 10.60 Å) to partition NU-1501, but only got non-partitioned acs structures. For reference, d p for P1, P2, and P3 is 6.93 Å, 10.02 Å, 9.91 Å respectively. Compared with NNM-750-752 based on trigonal prismatic ligands with stereo iptycene core 22-24 , the discovery of NNM-753 is special because it is predicted and synthesized by only considering the size relation of P1 and L3 with no parent acs structure reported before (Supplementary Fig. 8 and Fig. 9). In L3, the introduction of three steric methyl groups on the centered benzene twists the ligand conformation from planar to trigonal prism 25,26 . In fact, we have tried but failed to obtain its corresponding non-partitioned acs structure, indicative of the power of PSP strategy to direct the assembly of the partitioned framework. Another interesting point here is the use of anionic P1 ligand in NNM-750 and NNM-753. The anionic feature of P1 ligand comes from the acidic central N-rich hexaazaphenalene ring with the presence of six nitrogens to resonance-stabilize the anionic site 27-30 . The large aromatic plane enables a strong π–π interaction and the six nitrogens in the hexaazaphenalene core can be involved in multiple H-bonds, which could be beneficial for the adsorption of aromatic guest such as benzene as discussed below. In addition, the combination of cationic metal trimers of [M 3 O(COOR) 6 ] + and anionic ligand P1 - in NNM-750 and -753 with 1 : 1 ratio leads to a neutral framework. In comparison, NNM-751 and -752 are cationic. The PSP on prototypical flexible acs and rigid acs frameworks share some common features. The connectivity of metal trimer increases from 6 to 9, accompanied with the annihilation of all the open metal after incorporating the tritopic P ligands (Fig. 2b and Supplementary Fig. 10). The consecutive hexagonal channel along c direction is partitioned into infinite number of small segments (Fig. 2c,d). The differences between rigid acs and prototypical flexible acs framework set off a chain reaction in the partitioned frameworks. Compared with prototypical acs , the loss of half metal trimers in NU-1500 structures has led to the loss of half partitioned ligands in NNM MOFs. As such, the distance between adjacent partitioned ligands is just equal to cell length of c axis in NNM MOFs while it is equal to c /2 in partitioned flexible acs . The stacking of the partition ligands also changed from ABAB stacking with a rotation degree of 60 o to an eclipsed stacking fashion, which results in a more open channel along c direction (Fig. 2c and Supplementary Fig. 11). In addition, the original pacs structures has a (3, 9)-c nia-d topology, while NNM MOFs here have a (3, 6, 9)-c 3-nodal net with a new topology (detailed topological analysis in Page 45 of SI). All the Cr phases were prepared in the polycrystalline form with the size around hundreds of nanometers with in-situ one-pot reactions (Supplementary Fig. 12-15). The isomorphic structures of Cr MOFs and Fe MOFs were identified by comparing their powder diffraction patterns and FTIR spectra (Supplementary Fig. 16 and Fig. 17). In particular, the NNM MOFs exhibit a strong diffraction peak that belongs to (001) lattice plane caused by the partitioning ligand, dramatically different from those non-partitioned structures (Supplementary Fig. 18). Rietveld refinements were also carried out on Cr phase. The resulted refined patterns fit well with experimental ones with low residual values, further verified their structures (Supplementary Fig. 19 and Table 5-8). The use of trigonal prismatic ligands as organic vertices in NU-1500 MOFs has led to a low metal density and the introduction of P ligands here made it even lower. Supplementary Table 9 shows the theoretical metal-site densities of some highly porous MOFs 31 . Highly porous DUT-6 has a metal density of 3.73 mmol g -1 . NU-1500(Cr) has a low metal density of 2.52 mmol g -1 . NNM MOFs here has much lower metal density, from 1.39 to 1.94 mmol g -1 . In particular, NNM-752-Fe has a metal density of 1.39 mmol g -1 , resulting in a near-organic backbone with metal mass fraction as low as 5%. Such lightweight frameworks of NNM-MOFs are beneficial for high guest uptake. Porosity and chemical stability. The permanent porosity of eight NNMs, after thermal activation from dichloromethane-exchanged samples, was analyzed through N 2 adsorption at 77 K. Among them, NNM-750 and NNM-753 show reversible type-I isotherms, while the isotherms for NNM-751 and NNM-752 are slightly different due to the existence of larger pores. The pore-size distribution based on a density functional theory (DFT) model reveal that NNM-750 have pore size ranging from 0.5 nm to 1.2 nm, NNM-751/752 ranging from 0.5 nm to 2.0 nm, and NNM-753 ranging from 0.6 nm to 1.2 nm (Supplementary Fig. 20). The Brunauer-Emmett-Teller (BET) surface areas of NNM-750~753(Fe) were calculated to be 2387, 3514, 4084 and 2845 m 2 g -1 , while NNM-750~753(Cr) are 2388, 2083, 2714 and 2097 m 2 g -1 , after satisfying all four BET consistency criteria with BETSI software (Fig. 3a and Supplementary Fig. 21-28) 32,33 . The coordinating saturation of metal sites in combination with the rigid backbone contributed to high structural stability. Thermogravimetric analysis (TGA) curves for NNMs show only slight weight losses (< 8%, corresponding to the release of adsorbed solvents) before 400 o C, suggesting their good thermostability (Fig. 3b). Due to the highest inertness of Cr (III) among all the metal cations used in MOFs, the chemical stability of Cr based NNMs were studied 34,35 . NNM-750-Cr and NNM-752-Cr were chosen to evaluate the chemical stability. After immersing into boiling water, concentrated hydrochloric acid (12 M), and 1 M sodium hydroxide solution for 24 h, both of two structures retained high crystallinity, as suggested by PXRD patterns (Fig. 3c,e). N 2 adsorption isotherms further confirmed the high stability under harsh conditions (Fig. 3d,f). Improved N 2 uptake after boiling water or acid treatments is likely due to the additional activation effect. A small decrease of N 2 uptake can be observed with the treatment of 1 M NaOH, probably due to the partial decomposition of the structure. The resistance to strong bases by Cr MOFs here is notable, considering that most prior Cr-MOFs have a basic resistance lower than pH 12 36 . It could be concluded that the incorporation of partitioning ligands endows the Cr based highly porous NNMs with ultrastability, among the best stable MOFs (Supplementary Table 10) 36-42 . Benzene adsorption performance. NNMs with excellent structural stability, highly conjugated aromatic backbone are suitable for aromatic VOCs adsorption related applications, such as trace removal of benzene. Single-component benzene adsorption measurements on NNMs were conducted at 298 K. For comparison, benzene adsorption isotherms for non-partitioned structures MIL-88-Fe, NU-1500-Fe and NU-1501-Fe were also collected. As shown in Figure 4a and Figure S29, all the samples exhibit sharply benzene uptake at low pressure, suggesting the strong interaction between host framework and benzene. The saturated benzene capture capacity for most Fe based NUs and NNMs is positively correlated with the extra-framework volume and is determined to be 11.03 mmol/g for NU-1500-Fe, 10.35 mmol/g for NNM-750-Fe, 15.31 mmol/g for NNM-751-Fe, 17.57 mmol/g for NNM-752-Fe, 8.41 mmol/g for NNM-753-Fe. The adsorption capacity of NU-1501-Fe is only 3.86 mmol/g, which is probably due to the partial collapse of the structure, as suggested by PXRD patterns (Supplementary Fig. 30). The uptake for Cr based NNM-750-753 is determined to be 8.43, 9.48, 13.65 and 5.46 mmol/g, respectively. While the flexible MIL-88-Fe showed negligible benzene adsorption at low pressure (Supplementary Fig. 31), it is worth noting that the partitioned structures exhibit enhanced capture capacity at low vapor pressure (P/P 0 < 0.01) compared to non-partitioned structures. For example, at P/P 0 = 0.01, the benzene uptake for NNM-750-Fe and NU-1500-Fe is almost the same. However, when P/P 0 is equal to 0.005, the benzene uptake for NNM-750-Fe is about 7.92 mmol/g, almost three times of NU-1500-Fe’s (2.74 mmol/g). At P/P 0 = 0.002, the benzene uptake for NNM-750-Fe still reaches up to 6.02 mmol/g but NU-1500-Fe could only adsorb 0.84 mmol/g (Fig. 4b). NNM-750-Fe set a new benchmark for trace benzene capture which shows the highest benzene capture capacity at a wide pressure range and far exceeds previous records. At 298 K and P/P 0 = 0.01, the benzene adsorption capacity for NNM-750-Fe is 8.97 mmol g -1 , which outperform other previously reported benzene adsorbents such as MOF-74-Mn (6.30 mmol g -1 ), ZJU-520-Al (5.98 mmol g -1 ), BUT-54-Co (4.31 mmol g -1 ), UiO-66-Cu(II) (3.92 mmol g -1 ), ZJU-620-Al (3.80 mmol g -1 ), and PAF-1 (3.66 mmol g -1 ) (Fig. 4c, Supplementary Table 11) 43-49 . The record trace benzene capture capacity is identified at a wide range of relative pressure from 0.003 to 0.01 (Fig. 4d). The volumetric benzene capture for NNM-750-Fe is only second to Mn-MOF-74 at P/P 0 = 0.01 but is significantly higher than Mn-MOF-74 and other samples at lower pressure (Fig. 4c,d). We also carried out multiple benzene adsorption and desorption experiments on NNM-750 at 298 K to evaluate their durability and recyclability (Fig. 4e). There is no obvious decrease of benzene uptake capability after 3 adsorption-desorption cycles and PXRD patterns also showed that NNM-750 still had a good crystallinity after benzene adsorption, indicating the high structural robustness and excellent regeneration ability (Supplementary Fig. 32). Dynamic gas breakthrough experiments at 298 K were carried out on NNM-750-Fe and NU-1500-Fe to further evaluate their ability to capture low-concentration benzene. A gas mixture of benzene vapor (1000 ppm) and nitrogen with the molar ratio of 1 : 4 was passed through a column packed with 50 mg NNM-750 sorbents or NU-1500- Fe at a total gas flow rate of 50 mL min -1 . As shown in Figure 4f, the benzene starts to break through the column of NU-1500-Fe after 2.07 h (41.37 h g -1 ), corresponding to the benzene capture capacity of 1.11 mmol g -1 . After the pore-space-partition by P1 ligand, the breakthrough of benzene in the resulting NNM-750-Fe delayed to 4.06 h (81.10 h g -1 ) corresponding to the benzene capture capacity of 2.17 mmol g -1 . This result further demonstrates that PSP in NU-1500 greatly promote low-concentration benzene capture from air. DFT calculations for benzene adsorption sites. To uncover the underlying reason for the contribution of PSP on the boosted benzene adsorption, DFT calculations were conducted to investigate the benzene adsorption in NU-1500-Fe and NNM-750-Fe. For NU-1500, benzene molecule can form multiple C-H···C interactions and C-H···π interactions with the benzene ring at three corners of the trigonal prismatic ligands (site A), affording a moderately high binding energy of -49.70 kJ mol -1 (Fig. 5a). Another adsorption site (site B) in NU-1500 is the Fe OMS with Fe-C distances being 3.298 and 3.424 Å, respectively (Fig. 5b). However, the binding energy is only -31.15 kJ mol -1 . NNM-750 possesses the same benzene adsorption site around the trigonal prismatic ligand (site A) and very similar binding energy (-45.76 kJ mol -1 ) (Fig. 5d). Although the OMS site of NU-1500 was blocked after the implementation of PSP , but in the meantime the inserted P1 linker provided additional adsorption site (site B’) (Fig. 5e). Notably, the large π-conjugated hexaazaphenalene-based ligand in NNM-750 can interact with coplanar benzene molecule by π···π stacking, with the C-N distances varying from 3.560 to 3.794 Å. Meanwhile, the N atoms of the inserted P1 ligand can also form multiple intermolecular hydrogen bonds with the H atom in benzene, and the N···H distances are 3.413-3.432 Å. The combined π···π stacking and multiple hydrogen bonds interactions endow NNM-750 higher benzene affinity and the binding energy is as high as -79.91 kJ mol -1 . Besides, to display the host-guest interaction visually, independent gradient model (IGM) analysis was employed. As shown in Figure 5c and Figure S33, the green isosurfaces indicate that NU-1500 exists Van der Waals interaction with benzene molecule at the corner of triene unit and Fe OMS site. IGM analysis also shows a green isosurface between benzene molecule and P1 motif in NNM-750, which is fatter and larger than that in site B in NU-1500 (Fig. 5f), demonstrating stronger benzene affinity of NNM-750. This is in line with the experimental results that NNM-750 exhibits significantly improved benzene adsorption performances at low pressure compared with NU-1500. In summary, in this work, we have demonstrated the successful implementation of PSP strategy in a series of rigid and lightweight acs type frameworks based on 6-connected trigonal prismatic linkers as organic vertices. Eight MOFs with four ligand pairs and two metals were made. The introduction of pyridyl ligands with aromatic backbone and the lightweight framework of NNM MOFs has contributed to record-high trace benzene adsorption, which far exceeds previous record at a wide range of pressure. DFT calculations indicated that the use of hexaazaphenalene-based ligand has a much higher binding energy than that of open metal sites. The PSP on rigid acs frameworks here significantly broaden the application of PSP concept and therefore highlight new possibilities for the construction of new pacs MOFs. In addition, the use of large π-conjugated hexaazaphenalene-based ligand in other chemical systems may also have promising applications for the adsorption of aromatic guests Method All reagents were obtained from commercial sources and used without further purification. Synthesis of P1 (HTPH) P1 was synthesized according to the literature 20 . NaC(CN) 3 (0.750g, ~6.6 mmol) and pyridine-4-amidine hydrochloride (4.50 g, ~28 mmol) were ground in an agate mortar to achieve thorough mixing, then transferred to a 23 mL teflon-lined autoclave and then heated at 200 o C overnight. After cooled to ambient temperature, 10 wt% HCl solution was added to dissolve the crude product. After filtering undissolved particulates, the solution was neutralized with acetone, and isolated. The dissolution in HCl and neutralization in acetone were repeated twice. The product was isolated and dried overnight under vacuum at 60 o C to obtain the final light tan P1 powder. Synthesis of NNM-750-Fe [Fe 3 O(L1)(P1)] (single crystal) FeCl 3 ·6H 2 O (20 mg, ~0.074 mmol), L1 (10 mg, ~0.01 mmol), P1 (5 mg, ~0.012 mmol), DMF (3.5 mL) and TFA (400 μL) were added in 15 mL glass vial and then ultrasonically treated for 10 min. The vial was placed in 150 o C oven for 7 h. Russet triangular prism or hexagonal flake-like NNM-750-Fe crystals were obtained after cooling to room temperature. The yield was about 70% based on the Fe (Experimental: ~27 mg; Theoretical: 38.5 mg). The phase purity was identified by the powder X-ray diffraction. Synthesis of NNM-751-Fe [Fe 3 O(L2)(P2)(Cl) x (TFA) 1-x ] (single crystal) FeCl 3 ·6H 2 O (12 mg, ~0.044 mmol), L2 (10 mg, ~0.007 mmol), P2 (8 mg, ~0.015 mmol), DMF (3.5 mL) and TFA (200 μL) were added in 15 mL glass vial and then ultrasonically treated for 10 min. The vial was placed in 150 o C oven for 7 h. Russet triangular or hexagonal flake-like NNM-751-Fe crystals were obtained after cooling to room temperature. The yield was about 70% based on the Fe. The phase purity was identified by the powder X-ray diffraction. Synthesis of NNM-752-Fe [Fe 3 O(L2)(P3)(Cl) x (TFA) 1-x ] (single crystal) FeCl 3 ·6H 2 O (6 mg, ~0.022 mmol), L2 (10 mg, ~0.007 mmol), P3 (4 mg, ~0.007 mmol), DMF (3.5 mL) and TFA (100 μL) were added in 15 mL glass vial and then ultrasonically treated for 10 min. The vial was placed in 150 o C oven for 7 h. Russet triangular or hexagonal flake-like NNM-752-Fe crystals were obtained after cooling to room temperature. The yield was about 80% based on the Fe. The phase purity was identified by the powder X-ray diffraction. Synthesis of NNM-753-Fe [Fe 3 O(L3)(P1)] (single crystal) FeCl 3 ·6H 2 O (8 mg, ~0.030 mmol), L3 (10 mg, ~0.009 mmol), P1 (4 mg, ~0.007 mmol), DMF (3.5 mL) and TFA (400 μL) were added in 15 mL glass vial and then ultrasonically treated for 10 min. The vial was placed in 150 o C oven for 7 h. Russet triangular flake-like NNM-753-Fe crystals were obtained after cooling to room temperature. The yield was about 60% based on the Fe. The phase purity was identified by the powder X-ray diffraction. Synthesis of NNM-750-Cr [Cr 3 O(L1)(P1)] (powder sample) Cr(NO 3 )·9H 2 O (144 mg, ~0.360 mmol), L1 (146 mg, ~0.150 mmol), P1 (48 mg, ~0.119 mmol), H 2 O (2 mL), Py (3 mL) and HF (100 μL) were added in 15 mL glass vial and then ultrasonically treated for 10 min. The mixture was transferred into the teflon-lined stainless-steel autoclave and the vessel was subsequently placed in a 220 o C preheated oven for 24 h. After allowing vessel to cool to ambient temperature, the obtained powder sample of NNM-750-Cr was collected by centrifuge under 3000 r/min after washing with DMF and EtOH. Synthesis of NNM-751-Cr [Cr 3 O(L2)(P2)(NO 3 ) x (F) 1-x ] (powder sample) Cr(NO 3 )·9H 2 O (144 mg, ~0.360 mmol), L2 (215 mg, ~0.150 mmol), P2 (65 mg, ~0.119 mmol), H 2 O (2 mL), Py (3 mL) and HF (100 μL) were added in 15 mL glass vial and then ultrasonically treated for 10 min. The mixture was transferred into the teflon-lined stainless-steel autoclave and the vessel was subsequently placed in a 220 o C preheated oven for 24 h. After allowing vessel to cool to ambient temperature, the obtained powder sample of NNM-751-Cr was collected by centrifuge under 3000 r/min after washing with DMF and EtOH. Synthesis of NNM-752-Cr [Cr 3 O(L2)(P3)(NO 3 ) x (F) 1-x ] (powder sample) Cr(NO 3 )·9H 2 O (144 mg, ~0.360 mmol), L2 (215 mg, ~0.150 mmol), P3 (65 mg, ~0.119 mmol), H 2 O (2 mL), Py (3 mL) and HF (100 μL) were added in 15 mL glass vial and then ultrasonically treated for 10 min. The mixture was transferred into the teflon-lined stainless-steel autoclave and the vessel was subsequently placed in a 220 o C preheated oven for 24 h. After allowing vessel to cool to ambient temperature, the obtained powder sample of NNM-752-Cr was collected by centrifuge under 3000 r/min after washing with DMF and EtOH. Synthesis of NNM-753-Cr [Cr 3 O(L3)(P1)] (powder sample) Cr(NO 3 )·9H 2 O (144 mg, ~0.360 mmol), L3 (158 mg, ~0.148 mmol), P1 (48 mg, ~0.119 mmol), H 2 O (2 mL), Py (3 mL) and HF (100 μL) were added in 15 mL glass vial and then ultrasonically treated for 10 min. The mixture was transferred into the teflon-lined stainless-steel autoclave and the vessel was subsequently placed in a 220 o C preheated oven for 24 h. After allowing vessel to cool to ambient temperature, the obtained powder sample of NNM-753-Cr was collected by centrifuge under 3000 r/min after washing with DMF and EtOH. Synthesis of NU-1500-Fe (single crystal) NU-1500-Fe was synthesized according to the literature 11 . FeCl 3 ·6H 2 O (20 mg, ~0.074 mmol), L1 (10 mg, ~0.01 mmol), DMF (3 mL) and TFA (500 μL) were added in 30 mL glass vial and then ultrasonically treated for 10 min. The vial was placed in 150 o C oven for 12 h. Pure yellow-orange prismatic block crystals were obtained after cooling to room temperature. Synthesis of MIL-88-Fe (powder sample) MIL-88-Fe was synthesized according to the literature 50 . FeCl 3 ·6H 2 O (0.187 g, ~0.693 mmol) and terephthalic acid (BDC, 0.126 g, ~0.759 mmol) were dissolved in 15 mL of DMF, and the mixed solution was ultrasonically dispersed for 20 min. Then, the solution was transferred to a 23 mL Tefion-lined reactor at 120 o C for 8 h. After cooled to room temperature, the precipitate was separated by centrifugation. Declarations Data availability Crystallographic data for the structures reported in this article have been deposited at the Cambridge Crystallographic Data Centre, under deposition numbers CCDC 2357819 (NNM-750-Fe), 2357820 (NNM-751-Fe), 2357821 (NNM-752-Fe), 2357822 (NNM-753-Fe), 2358289 (NNM-750-Cr), 2357858 (NNM-751-Cr), 2357859 (NNM-752-Cr) and 2357860 (NNM-753-Cr). These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif. The data supporting the findings of this study are available in the Supplementary Information. Acknowledgements We acknowledge the financial support from National Natural Science Foundation of China (Grant No. 22301138 and 22201117), Jiangsu Specially Appointed Professorship, and the startup funding from Nanjing Normal University. We thank Dr. Zhenyi Zhang from Bruker (Beijing) Scientific Technology Co., Ltd. for SCXRD analysis. Author contributions H.J.Y. and C.Z.X. conceived the project. 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Commun. 15 , 3204, (2024). Hu, C. et al. Enhancing the peroxidase-like activity of MIL-88B by ligand exchange with polydopamine. Dalton Trans. 51 , 2262-2268, (2022). Additional Declarations There is NO Competing Interest. Supplementary Files NMSI.docx TOC.png Cite Share Download PDF Status: Under Review Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-4530984","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":313508277,"identity":"1b133466-2477-45cc-b139-f7334c2a8ca2","order_by":0,"name":"Huajun 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03:00:12","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4530984/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4530984/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":58358095,"identity":"1ff271e9-591a-4dd8-a61e-a8f0e4a2fe04","added_by":"auto","created_at":"2024-06-14 10:30:38","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":292015,"visible":true,"origin":"","legend":"\u003cp\u003eIllustration for the difference of \u003cstrong\u003ePSP\u003c/strong\u003e on prototypical flexible \u003cstrong\u003eacs\u003c/strong\u003e framework and rigid \u003cstrong\u003eacs\u003c/strong\u003e framework.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-4530984/v1/eff5bb9d73bf00921ef3e628.png"},{"id":58358097,"identity":"230a4dcf-70df-4075-951d-d5f0b2bfa8ba","added_by":"auto","created_at":"2024-06-14 10:30:38","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":1121131,"visible":true,"origin":"","legend":"\u003cp\u003eStructural illustrations of NNM MOFs reported in this work. (a) Trigonal prismatic ligands and partitioning ligands used in this work. (b) Nine-connected metal-trimer in NNM-750. (c) Illustration of \u003cstrong\u003ePSP \u003c/strong\u003estrategy on NU-1500-type MOFs. (d) Side view of partitioned hexagonal channels in NNMs. (L1 = 4,4',4'',4''',4'''',4'''''-(9,10-dihydro-9,10-[1,2]benzenoanthracene-2,3,6,7,14,15-hexayl)hexabenzoic acid; L2 = 4',4''',4''''',4''''''',4''''''''',4'''''''''''-(9,10-dihydro-9,10-[1,2]benzenoanthracene-2,3,6,7,14,15-hexayl)hexakis([1,1'-biphenyl]-4-carboxylic acid; L3 = 5',5'''-Bis(4-carboxyphenyl)-5''-(4,4''-dicarboxy[1,1':3',1''-terphenyl]-5'-yl)-2'',4'',6''-trimethyl[1,1':3',1'':3'',1''':3''',1'''''-quinquephenyl]-4,4'''''-dicarboxylic acid; P1 = 2,5,8-tri-(4-pyridyl)-1,3,4,6,7,9-hexaazaphenalene; P2 = 4,4'-(5'-(4-(Pyridin-4-yl)phenyl)-[1,1':3',1''-terphenyl]-4,4''-diyl)dipyridine; P3 = 2,4,6-Tris(4-(pyridin-4-yl)phenyl)-1,3,5-triazine; green atom: Fe or Cr; red atom: O; gray atom: C; wathet atom: N)\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-4530984/v1/e7a941b25a76c478e69371da.png"},{"id":58358100,"identity":"440798db-cf3b-4684-b465-d519b7b26451","added_by":"auto","created_at":"2024-06-14 10:30:38","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":471972,"visible":true,"origin":"","legend":"\u003cp\u003e(a) N\u003csub\u003e2\u003c/sub\u003e adsorption isotherms at 77 K for eight NNMs measured. (b) TG curves for eight NNMs. (c-f) PXRD pat-terns and N\u003csub\u003e2\u003c/sub\u003e uptake (77 K) of NNM-750-Cr (c, d) and NNM-752-Cr (e, f) after boiling water, concentrated HCl and NaOH solution treatments.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-4530984/v1/ce909bf5a67da7c244638ea1.png"},{"id":58358098,"identity":"83c169df-03b6-4e84-96b9-01f67bcd02bd","added_by":"auto","created_at":"2024-06-14 10:30:38","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":414720,"visible":true,"origin":"","legend":"\u003cp\u003e\u0026nbsp;(a) Benzene adsorption isotherms of all NNMs at 298 K. (b) Comparison of benzene adsorption of NNM-750-Fe and NU-1500-Fe at low pressure. (c) Comparison of gravimetric benzene uptake and volumetric benzene uptake for NNM-750-Fe/Cr, NNM-753-Fe/Cr, NU-1500-Fe, and other benchmark porous structures at P/P\u003csub\u003e0\u003c/sub\u003e = 0.01. (d) Comparison the gravimetric benzene capture capacity at relative pressure of 0.003 and 0.005. (e) Three cycles of benzene adsorption capacity at P/P\u003csub\u003e0\u003c/sub\u003e = 0.01 of NNM-750-Fe/Cr. (f) Breakthrough curves for NNM-750-Fe and NU-1500-Fe at the same conditions.\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-4530984/v1/13714eab0597eac6eda34d84.png"},{"id":58358101,"identity":"0e5b627b-f005-4411-be1b-4547130c0838","added_by":"auto","created_at":"2024-06-14 10:30:38","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":612057,"visible":true,"origin":"","legend":"\u003cp\u003eThe DFT-calculated configurations of benzene at site A (a) and site B (b) in NU-1500; The DFT-calculated configurations of benzene at site A (d) and site B’ (e) in NNM-750; The IGM isosurfaces for benzene at Fe OMS site (site B) in NU-1500 (c) and at hexaazaphenalene core site (site B') in NNM-750 (f). Green, Fe; red, O; gray, C; light green, H; wathet, N.\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-4530984/v1/fbb17387e4a80b19f55f57c9.png"},{"id":58359242,"identity":"23a9b933-9d7e-4ec0-87a9-08c8f08c694a","added_by":"auto","created_at":"2024-06-14 10:46:39","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":3802283,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4530984/v1/6a9a5e6b-a8c5-49ff-b489-51435dd2e959.pdf"},{"id":58358105,"identity":"d12c2571-df5f-4bf2-80ce-57bb6c29a058","added_by":"auto","created_at":"2024-06-14 10:30:38","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":11991624,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cbr\u003e\u003c/p\u003e","description":"","filename":"NMSI.docx","url":"https://assets-eu.researchsquare.com/files/rs-4530984/v1/b6fd567ec118bd916188304f.docx"},{"id":58358703,"identity":"7cbab5e9-bc43-4085-a7be-dc6119162500","added_by":"auto","created_at":"2024-06-14 10:38:38","extension":"png","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":32855,"visible":true,"origin":"","legend":"","description":"","filename":"TOC.png","url":"https://assets-eu.researchsquare.com/files/rs-4530984/v1/2e627504d63b020288daeec4.png"}],"financialInterests":"There is \u003cb\u003eNO\u003c/b\u003e Competing Interest.","formattedTitle":"Pore Space Partition in Rigid Metal-Organic Frameworks Containing Organic Vertices for Trace Benzene Adsorption","fulltext":[{"header":"Introduction","content":"\u003cp\u003eMetal-organic frameworks (MOFs) are built by connecting metal-containing secondary building units (SBUs) with organic ligands\u003csup\u003e1\u003c/sup\u003e. In general, the inorganic SBUs is treated as vertex and the organic ligands is treated as linkers in simplifying the MOF structures\u003csup\u003e2-6\u003c/sup\u003e. However, the high-connected organic linkers have made the line between such structural roles of inorganic components and organic components blurred and sometimes the roles were even reversed\u003csup\u003e7-9\u003c/sup\u003e. For example, MOF-688 had a \u003cstrong\u003edia\u003c/strong\u003e topology with 4-connected tetrahedral tetrakis(4-formylphenyl)methane organic building units as vertices and 2-connected polyoxometalate cluster as linkers\u003csup\u003e10\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003eCompared to MOFs built on inorganic vertices, a potential advantage of MOFs with part or all organic vertices is the lightweight framework, which is beneficial for high guest uptake in adsorption applications. An excellent example is the series of NU-1500 structures with an \u003cstrong\u003eacs\u003c/strong\u003e topology, which is built on trivalent trinuclear metal (Fe\u003csup\u003e3+\u003c/sup\u003e, Cr\u003csup\u003e3+\u003c/sup\u003e, Al\u003csup\u003e3+\u003c/sup\u003e and Sc\u003csup\u003e3+\u003c/sup\u003e) clusters and trigonal prismatic ligands\u003csup\u003e11,12\u003c/sup\u003e. A main difference of NU-1500 from prototypical \u003cstrong\u003eacs\u003c/strong\u003e (MOF-235/MIL-88) is half of the 6-connected inorganic node is substituted by 6-connected organic vertices, resulting a rigid framework\u003csup\u003e13-15\u003c/sup\u003e. NU-1500-Cr showed an impressive water uptake and NU-1501-Al with high porosity and surface area yielded a methane storage capacity over U.S. Department of Energy target \u003csup\u003e11,12\u003c/sup\u003e. With the lightweight frameworks, however, the pore size of NU-1500 structures is too large to enable a strong host-guest interaction to confine the small molecules for adsorption/separation applications at ambient conditions.\u003c/p\u003e\n\u003cp\u003ePore-space-partition (\u003cstrong\u003ePSP\u003c/strong\u003e) strategy, which refers to the division of large pores into small segments, is a fruitful approach to increase the density of binding sites and has achieved great experimental success\u003csup\u003e16-20\u003c/sup\u003e. Of potential relevance to NU-1500 structures is that \u003cstrong\u003ePSP\u003c/strong\u003e has been proved to be incredibly successful in \u003cstrong\u003eacs\u003c/strong\u003e topology by introducing a symmetry-matched pore-partitioning agent into the flexible \u003cstrong\u003eacs\u003c/strong\u003e framework\u003csup\u003e13,14\u003c/sup\u003e. The partitioned \u003cstrong\u003eacs\u003c/strong\u003e (\u003cstrong\u003epacs\u003c/strong\u003e) platform rank among the best MOFs in a range of properties such as high gas up-take and high chemical stability\u003csup\u003e21\u003c/sup\u003e. We are thus intrigued by the prospect that the implementation of \u003cstrong\u003ePSP\u003c/strong\u003e on lightweight NU-1500 structures may set new adsorption record. The aromatic guest would be of particular interest due to introduction of \u0026pi;-conjugated partitioning ligand.\u003c/p\u003e\n\u003cp\u003eThe application of the \u003cstrong\u003ePSP\u003c/strong\u003e strategy on NU-1500 frameworks faces an extra hurdle because the directional nature of covalent bond in organic vertex has led to a rigid \u003cstrong\u003eacs\u003c/strong\u003e framework (Fig. 1)\u003csup\u003e11\u003c/sup\u003e. This is different from the case in previously reported flexible \u003cstrong\u003eacs\u003c/strong\u003e phases based on ditopic carboxylate ligands. Due to the nondirectional nature of metal-carboxylate bonds, they showed large size tolerance toward pore-partitioning agent\u003csup\u003e20\u003c/sup\u003e. As a consequence, in addition to symmetry match, strict size match between the partitioning agent and the framework is required for \u003cstrong\u003ePSP\u003c/strong\u003e on NU-1500 frameworks.\u003c/p\u003e\n\u003cp\u003eWith the above considerations in mind, in this work, we were able to make eight MOFs with four ligand pairs and two trivalent metals (Fe\u003csup\u003e3+\u003c/sup\u003e, Cr\u003csup\u003e3+\u003c/sup\u003e). The NNM MOFs (NNM stands for Nanjing Normal University Materials) reported here integrated ultralow metal density, high porosity, and high structural stability. Cr based NNMs show ultrastability which can withstand extreme pH conditions from concentrated hydrochloric acid to 1 M NaOH solution. NNMs with high porosity exhibit top-level adsorption performance toward volatile organic compound of benzene due to the introduction of conjugated partitioning ligand. Especially for NNM-750 structures, which show record capture capacity at ambient temperature and a wide range of relative pressure.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ePSP on rigid acs and structural analysis.\u003c/strong\u003e A main issue for \u003cstrong\u003ePSP\u003c/strong\u003e in NU-1500 frameworks based on the trigonal prismatic linkers is the rigidity of the framework inherited from rigid organic nodes. A closer look at the structure showed that the motion of metal carboxylate bond at the cluster is restricted by the directional C-C bonding at the linkers, leading to a rigid \u003cstrong\u003eacs\u003c/strong\u003e framework (Fig. 1). As such, the implementation of \u003cstrong\u003ePSP\u003c/strong\u003e strategy here requires an extra size match between the partitioning ligand (\u003cstrong\u003eP\u003c/strong\u003e) and trigonal prismatic ligand (\u003cstrong\u003eL\u003c/strong\u003e) in addition to symmetry match in prototypical flexible \u003cstrong\u003eacs\u003c/strong\u003e. (Supplementary Fig. 1).\u003c/p\u003e\n\u003cp\u003eBased on the geometry of the framework, a linear equation was derived to determine the relation between the size of trigonal prismatic linkers and the partitioning ligands. \u003cem\u003ed\u003c/em\u003e\u003csub\u003eL\u003c/sub\u003e is defined as the length of \u003cstrong\u003eL\u003c/strong\u003e projected onto \u003cem\u003ec\u003c/em\u003e plane where the length of \u003cstrong\u003eL\u003c/strong\u003e is the length from the center of \u003cstrong\u003eL\u003c/strong\u003e to the center of two terminal carboxylate oxygens. The \u003cstrong\u003eP\u003c/strong\u003e-related size (\u003cem\u003ed\u003c/em\u003e\u003csub\u003eP\u003c/sub\u003e) is the distance from the center to terminal nitrogen atom on pyridine. The relation between \u003cem\u003ed\u003c/em\u003e\u003csub\u003eL\u003c/sub\u003e and \u003cem\u003ed\u003c/em\u003e\u003csub\u003eP\u003c/sub\u003e is finally determined to be \u003cem\u003ed\u003c/em\u003e\u003csub\u003eP\u003c/sub\u003e = \u003cem\u003ed\u003c/em\u003e\u003csub\u003eL\u003c/sub\u003e \u0026ndash; 1.8 \u0026Aring; (Supplementary Fig. 2). It could be deduced that four pairs of ligands match well for the implementation of \u003cstrong\u003ePSP\u003c/strong\u003e strategy (L1-P1 for NNM-750, L2-P2 for NNM-751, L2-P3 for NNM-752, and L3-P1 for NNM-753, Fig. 2a and Supplementary Fig. 3).\u003c/p\u003e\n\u003cp\u003eThe crystal size of all the Fe MOFs were suitable for single crystal X-ray diffraction (SCXRD) measurement (Supplementary Fig. 4). The detailed crystallographic information is shown in Supplementary Table 1-4. The experimental PXRD patterns of Fe phases matched well with simulated ones from single-crystal data, suggesting the phase purity of as-synthesized samples (Supplementary Fig. 5). SCXRD analysis suggests that the NNMs have lower symmetry compared with their parent structures. In particular, the partitioned NU-1500 (NNM-750) has a lowest space group of \u003cem\u003eP\u003c/em\u003e3, in comparison with \u003cem\u003eP\u003c/em\u003e-6\u003cem\u003em\u003c/em\u003e2 of NU-1500. Detailed structural analysis shows that the distances from 6-\u003cem\u003ec\u003c/em\u003e ligand to the trimers in NNM-750 are not consistent, with three shorter ones on one side and three longer ones on the other (Supplementary Fig. 6). Such a distortion is probably due to the subtle size mismatch between the framework and the ligands. The extra-framework volume for the NNMs were calculated to be 66.0 % (NNM-750), 77.1 % (NNM-751), 76.9 % (NNM-752) and 70.8 % (NNM-753) by using PLATON program, lower than their corresponding nonpartitioned structures due to the insertion of P ligands.\u003c/p\u003e\n\u003cp\u003eAn evidence for the size match is that the unit cells have remained essentially unchanged after \u003cstrong\u003ePSP\u003c/strong\u003e. For example, the \u003cem\u003ea\u003c/em\u003e-axis for NU-1500-Fe and NU-1501-Fe are 19.57 \u0026Aring; and 24.96 \u0026Aring;, while for \u003cstrong\u003ePSP\u003c/strong\u003e resulted NNM-750-Fe and NNM-751-Fe are 19.31 \u0026Aring; and 24.69 \u0026Aring; respectively, with the size difference smaller than 3 percent (Supplementary Fig. 7). The deviation is attributed to slight bending of the long branch of \u003cstrong\u003eL\u003c/strong\u003e ligands, and the size tolerance for partitioning ligand is expected to marginally increase with the length of the branch. Further controlled experiments were carried out to certify the rigorous size match for PSP. We have tried to use tripyridyl ligands with different size to partition the rigid NU-1500 and NU-1501, e.g., smaller \u003cstrong\u003eP\u003c/strong\u003e ligand of tpt (\u003cem\u003ed\u003c/em\u003e\u003csub\u003eP\u003c/sub\u003e = 5.55 \u0026Aring;) or bigger \u003cstrong\u003eP\u0026nbsp;\u003c/strong\u003eligand of tpbtc (\u003cem\u003ed\u003c/em\u003e\u003csub\u003eP\u003c/sub\u003e = 7.88 \u0026Aring;) to partition NU-1500; a slight bigger \u003cstrong\u003eP\u003c/strong\u003e of tpapa (\u003cem\u003ed\u003c/em\u003e\u003csub\u003eP\u003c/sub\u003e = 10.60 \u0026Aring;) to partition NU-1501, but only got non-partitioned \u003cstrong\u003eacs\u003c/strong\u003e structures. For reference, \u003cem\u003ed\u003c/em\u003e\u003csub\u003ep\u003c/sub\u003e for P1, P2, and P3 is 6.93 \u0026Aring;, 10.02 \u0026Aring;, 9.91 \u0026Aring; respectively.\u003c/p\u003e\n\u003cp\u003eCompared with NNM-750-752 based on trigonal prismatic ligands with stereo iptycene core\u003csup\u003e22-24\u003c/sup\u003e, the discovery of NNM-753 is special because it is predicted and synthesized by only considering the size relation of P1 and L3 with no parent \u003cstrong\u003eacs\u003c/strong\u003e structure reported before (Supplementary Fig. 8 and Fig. 9). In L3, the introduction of three steric methyl groups on the centered benzene twists the ligand conformation from planar to trigonal prism\u003csup\u003e25,26\u003c/sup\u003e. In fact, we have tried but failed to obtain its corresponding non-partitioned \u003cstrong\u003eacs\u003c/strong\u003e structure, indicative of the power of \u003cstrong\u003ePSP\u003c/strong\u003e strategy to direct the assembly of the partitioned framework.\u003c/p\u003e\n\u003cp\u003eAnother interesting point here is the use of anionic P1 ligand in NNM-750 and NNM-753. The anionic feature of P1 ligand comes from the acidic central N-rich hexaazaphenalene ring with the presence of six nitrogens to resonance-stabilize the anionic site\u003csup\u003e27-30\u003c/sup\u003e. The large aromatic plane enables a strong \u0026pi;\u0026ndash;\u0026pi; interaction and the six nitrogens in the hexaazaphenalene core can be involved in multiple H-bonds, which could be beneficial for the adsorption of aromatic guest such as benzene as discussed below. In addition, the combination of cationic metal trimers of [M\u003csub\u003e3\u003c/sub\u003eO(COOR)\u003csub\u003e6\u003c/sub\u003e]\u003csup\u003e+\u003c/sup\u003e and anionic ligand P1\u003csup\u003e-\u0026nbsp;\u003c/sup\u003ein NNM-750 and -753 with 1 : 1 ratio leads to a neutral framework. In comparison, NNM-751 and -752 are cationic.\u003c/p\u003e\n\u003cp\u003eThe \u003cstrong\u003ePSP\u003c/strong\u003e on prototypical flexible \u003cstrong\u003eacs\u003c/strong\u003e and rigid \u003cstrong\u003eacs\u003c/strong\u003e frameworks share some common features. The connectivity of metal trimer increases from 6 to 9, accompanied with the annihilation of all the open metal after incorporating the tritopic \u003cstrong\u003eP\u003c/strong\u003e ligands (Fig. 2b and Supplementary Fig. 10). The consecutive hexagonal channel along \u003cem\u003ec\u003c/em\u003e direction is partitioned into infinite number of small segments (Fig. 2c,d).\u003c/p\u003e\n\u003cp\u003eThe differences between rigid \u003cstrong\u003eacs\u003c/strong\u003e and prototypical flexible \u003cstrong\u003eacs\u003c/strong\u003e framework set off a chain reaction in the partitioned frameworks. Compared with prototypical \u003cstrong\u003eacs\u003c/strong\u003e, the loss of half metal trimers in NU-1500 structures has led to the loss of half partitioned ligands in NNM MOFs. As such, the distance between adjacent partitioned ligands is just equal to cell length of \u003cem\u003ec\u003c/em\u003e axis in NNM MOFs while it is equal to \u003cem\u003ec\u003c/em\u003e/2 in partitioned flexible \u003cstrong\u003eacs\u003c/strong\u003e. The stacking of the partition ligands also changed from ABAB stacking with a rotation degree of 60\u003csup\u003eo\u003c/sup\u003e to an eclipsed stacking fashion, which results in a more open channel along \u003cem\u003ec\u003c/em\u003e direction (Fig. 2c and Supplementary Fig. 11). In addition, the original \u003cstrong\u003epacs\u003c/strong\u003e structures has a (3, 9)-c nia-d topology, while NNM MOFs here have a (3, 6, 9)-c 3-nodal net with a new topology (detailed topological analysis in Page 45 of SI).\u003c/p\u003e\n\u003cp\u003eAll the Cr phases were prepared in the polycrystalline form with the size around hundreds of nanometers with in-situ one-pot reactions (Supplementary Fig. 12-15). The isomorphic structures of Cr MOFs and Fe MOFs were identified by comparing their powder diffraction patterns and FTIR spectra (Supplementary Fig. 16 and Fig. 17). In particular, the NNM MOFs exhibit a strong diffraction peak that belongs to (001) lattice plane caused by the partitioning ligand, dramatically different from those non-partitioned structures (Supplementary Fig. 18). Rietveld refinements were also carried out on Cr phase. The resulted refined patterns fit well with experimental ones with low residual values, further verified their structures (Supplementary Fig. 19 and Table 5-8).\u003c/p\u003e\n\u003cp\u003eThe use of trigonal prismatic ligands as organic vertices in NU-1500 MOFs has led to a low metal density and the introduction of \u003cstrong\u003eP\u003c/strong\u003e ligands here made it even lower. Supplementary Table 9 shows the theoretical metal-site densities of some highly porous MOFs\u003csup\u003e31\u003c/sup\u003e. Highly porous DUT-6 has a metal density of 3.73 mmol g\u003csup\u003e-1\u003c/sup\u003e. NU-1500(Cr) has a low metal density of 2.52 mmol g\u003csup\u003e-1\u003c/sup\u003e. NNM MOFs here has much lower metal density, from 1.39 to 1.94 mmol g\u003csup\u003e-1\u003c/sup\u003e. In particular, NNM-752-Fe has a metal density of 1.39 mmol g\u003csup\u003e-1\u003c/sup\u003e, resulting in a near-organic backbone with metal mass fraction as low as 5%. Such lightweight frameworks of NNM-MOFs are beneficial for high guest uptake.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ePorosity and chemical stability.\u003c/strong\u003e The permanent porosity of eight NNMs, after thermal activation from dichloromethane-exchanged samples, was analyzed through N\u003csub\u003e2\u003c/sub\u003e adsorption at 77 K. Among them, NNM-750 and NNM-753 show reversible type-I isotherms, while the isotherms for NNM-751 and NNM-752 are slightly different due to the existence of larger pores. The pore-size distribution based on a density functional theory (DFT) model reveal that NNM-750 have pore size ranging from 0.5 nm to 1.2 nm, NNM-751/752 ranging from 0.5 nm to 2.0 nm, and NNM-753 ranging from 0.6 nm to 1.2 nm (Supplementary Fig. 20). The Brunauer-Emmett-Teller (BET) surface areas of NNM-750~753(Fe) were calculated to be 2387, 3514, 4084 and 2845 m\u003csup\u003e2\u003c/sup\u003e g\u003csup\u003e-1\u003c/sup\u003e, while NNM-750~753(Cr) are 2388, 2083, 2714 and 2097 m\u003csup\u003e2\u003c/sup\u003e g\u003csup\u003e-1\u003c/sup\u003e, after satisfying all four BET consistency criteria with BETSI software (Fig. 3a and Supplementary Fig. 21-28)\u003csup\u003e32,33\u003c/sup\u003e.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe coordinating saturation of metal sites in combination with the rigid backbone contributed to high structural stability. Thermogravimetric analysis (TGA) curves for NNMs show only slight weight losses (\u0026lt; 8%, corresponding to the release of adsorbed solvents) before 400 \u003csup\u003eo\u003c/sup\u003eC, suggesting their good thermostability (Fig. 3b). Due to the highest inertness of Cr (III) among all the metal cations used in MOFs, the chemical stability of Cr based NNMs were studied\u003csup\u003e34,35\u003c/sup\u003e. NNM-750-Cr and NNM-752-Cr were chosen to evaluate the chemical stability. After immersing into boiling water, concentrated hydrochloric acid (12 M), and 1 M sodium hydroxide solution for 24 h, both of two structures retained high crystallinity, as suggested by PXRD patterns (Fig. 3c,e). N\u003csub\u003e2\u003c/sub\u003e adsorption isotherms further confirmed the high stability under harsh conditions (Fig. 3d,f). Improved N\u003csub\u003e2\u003c/sub\u003e uptake after boiling water or acid treatments is likely due to the additional activation effect. A small decrease of N\u003csub\u003e2\u003c/sub\u003e uptake can be observed with the treatment of 1 M NaOH, probably due to the partial decomposition of the structure. The resistance to strong bases by Cr MOFs here is notable, considering that most prior Cr-MOFs have a basic resistance lower than pH 12\u003csup\u003e36\u003c/sup\u003e. It could be concluded that the incorporation of partitioning ligands endows the Cr based highly porous NNMs with ultrastability, among the best stable MOFs (Supplementary Table 10)\u003csup\u003e36-42\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eBenzene adsorption performance.\u003c/strong\u003e NNMs with excellent structural stability, highly conjugated aromatic backbone are suitable for aromatic VOCs adsorption related applications, such as trace removal of benzene. Single-component benzene adsorption measurements on NNMs were conducted at 298 K. For comparison, benzene adsorption isotherms for non-partitioned structures MIL-88-Fe, NU-1500-Fe and NU-1501-Fe were also collected. As shown in Figure 4a and Figure S29, all the samples exhibit sharply benzene uptake at low pressure, suggesting the strong interaction between host framework and benzene. The saturated benzene capture capacity for most Fe based NUs and NNMs is positively correlated with the extra-framework volume and is determined to be 11.03 mmol/g for NU-1500-Fe, 10.35 mmol/g for NNM-750-Fe, 15.31 mmol/g for NNM-751-Fe, 17.57 mmol/g for NNM-752-Fe, 8.41 mmol/g for NNM-753-Fe. The adsorption capacity of NU-1501-Fe is only 3.86 mmol/g, which is probably due to the partial collapse of the structure, as suggested by PXRD patterns (Supplementary Fig. 30). The uptake for Cr based NNM-750-753 is determined to be 8.43, 9.48, 13.65 and 5.46 mmol/g, respectively. While the flexible MIL-88-Fe showed negligible benzene adsorption at low pressure (Supplementary Fig. 31), it is worth noting that the partitioned structures exhibit enhanced capture capacity at low vapor pressure (P/P\u003csub\u003e0\u003c/sub\u003e \u0026lt; 0.01) compared to non-partitioned structures. For example, at P/P\u003csub\u003e0\u003c/sub\u003e = 0.01, the benzene uptake for NNM-750-Fe and NU-1500-Fe is almost the same. However, when P/P\u003csub\u003e0\u003c/sub\u003e is equal to 0.005, the benzene uptake for NNM-750-Fe is about 7.92 mmol/g, almost three times of NU-1500-Fe\u0026rsquo;s (2.74 mmol/g). At P/P\u003csub\u003e0\u003c/sub\u003e = 0.002, the benzene uptake for NNM-750-Fe still reaches up to 6.02 mmol/g but NU-1500-Fe could only adsorb 0.84 mmol/g (Fig. 4b).\u003c/p\u003e\n\u003cp\u003eNNM-750-Fe set a new benchmark for trace benzene capture which shows the highest benzene capture capacity at a wide pressure range and far exceeds previous records. At 298 K and P/P\u003csub\u003e0\u003c/sub\u003e = 0.01, the benzene adsorption capacity for NNM-750-Fe is 8.97 mmol g\u003csup\u003e-1\u003c/sup\u003e, which outperform other previously reported benzene adsorbents such as MOF-74-Mn (6.30 mmol g\u003csup\u003e-1\u003c/sup\u003e), ZJU-520-Al (5.98 mmol g\u003csup\u003e-1\u003c/sup\u003e), BUT-54-Co (4.31 mmol g\u003csup\u003e-1\u003c/sup\u003e), UiO-66-Cu(II) (3.92 mmol g\u003csup\u003e-1\u003c/sup\u003e), ZJU-620-Al (3.80 mmol g\u003csup\u003e-1\u003c/sup\u003e), and PAF-1 (3.66 mmol g\u003csup\u003e-1\u003c/sup\u003e) (Fig. 4c, Supplementary Table 11)\u003csup\u003e43-49\u003c/sup\u003e. The record trace benzene capture capacity is identified at a wide range of relative pressure from 0.003 to 0.01 (Fig. 4d). The volumetric benzene capture for NNM-750-Fe is only second to Mn-MOF-74 at P/P\u003csub\u003e0\u003c/sub\u003e = 0.01 but is significantly higher than Mn-MOF-74 and other samples at lower pressure (Fig. 4c,d). We also carried out multiple benzene adsorption and desorption experiments on NNM-750 at 298 K to evaluate their durability and recyclability (Fig. 4e). There is no obvious decrease of benzene uptake capability after 3 adsorption-desorption cycles and PXRD patterns also showed that NNM-750 still had a good crystallinity after benzene adsorption, indicating the high structural robustness and excellent regeneration ability (Supplementary Fig. 32).\u003c/p\u003e\n\u003cp\u003eDynamic gas breakthrough experiments at 298 K were carried out on NNM-750-Fe and NU-1500-Fe to further evaluate their ability to capture low-concentration benzene. A gas mixture of benzene vapor (1000 ppm) and nitrogen with the molar ratio of 1 : 4 was passed through a column packed with 50 mg NNM-750 sorbents or NU-1500- Fe at a total gas flow rate of 50 mL min\u003csup\u003e-1\u003c/sup\u003e. As shown in Figure 4f, the benzene starts to break through the column of NU-1500-Fe after 2.07 h (41.37 h g\u003csup\u003e-1\u003c/sup\u003e), corresponding to the benzene capture capacity of 1.11 mmol g\u003csup\u003e-1\u003c/sup\u003e. After the pore-space-partition by P1 ligand, the breakthrough of benzene in the resulting NNM-750-Fe delayed to 4.06 h (81.10 h g\u003csup\u003e-1\u003c/sup\u003e) corresponding to the benzene capture capacity of 2.17 mmol g\u003csup\u003e-1\u003c/sup\u003e. This result further demonstrates that \u003cstrong\u003ePSP\u003c/strong\u003e in NU-1500 greatly promote low-concentration benzene capture from air.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eDFT calculations for benzene adsorption sites.\u003c/strong\u003e To uncover the underlying reason for the contribution of \u003cstrong\u003ePSP\u003c/strong\u003e on the boosted benzene adsorption, DFT calculations were conducted to investigate the benzene adsorption in NU-1500-Fe and NNM-750-Fe. For NU-1500, benzene molecule can form multiple C-H\u0026middot;\u0026middot;\u0026middot;C interactions and C-H\u0026middot;\u0026middot;\u0026middot;\u0026pi; interactions with the benzene ring at three corners of the trigonal prismatic ligands (site A), affording a moderately high binding energy of -49.70 kJ mol\u003csup\u003e-1\u003c/sup\u003e (Fig. 5a). Another adsorption site (site B) in NU-1500 is the Fe OMS with Fe-C distances being 3.298 and 3.424 \u0026Aring;, respectively (Fig. 5b). However, the binding energy is only -31.15 kJ mol\u003csup\u003e-1\u003c/sup\u003e. NNM-750 possesses the same benzene adsorption site around the trigonal prismatic ligand (site A) and very similar binding energy (-45.76 kJ mol\u003csup\u003e-1\u003c/sup\u003e) (Fig. 5d). Although the OMS site of NU-1500 was blocked after the implementation of \u003cstrong\u003ePSP\u003c/strong\u003e, but in the meantime the inserted P1 linker provided additional adsorption site (site B\u0026rsquo;) (Fig. 5e). Notably, the large \u0026pi;-conjugated hexaazaphenalene-based ligand in NNM-750 can interact with coplanar benzene molecule by \u0026pi;\u0026middot;\u0026middot;\u0026middot;\u0026pi; stacking, with the C-N distances varying from 3.560 to 3.794 \u0026Aring;. Meanwhile, the N atoms of the inserted P1 ligand can also form multiple intermolecular hydrogen bonds with the H atom in benzene, and the N\u0026middot;\u0026middot;\u0026middot;H distances are 3.413-3.432 \u0026Aring;. The combined \u0026pi;\u0026middot;\u0026middot;\u0026middot;\u0026pi; stacking and multiple hydrogen bonds interactions endow NNM-750 higher benzene affinity and the binding energy is as high as -79.91 kJ mol\u003csup\u003e-1\u003c/sup\u003e. Besides, to display the host-guest interaction visually, independent gradient model (IGM) analysis was employed. As shown in Figure 5c and Figure S33, the green isosurfaces indicate that NU-1500 exists Van der Waals interaction with benzene molecule at the corner of triene unit and Fe OMS site. IGM analysis also shows a green isosurface between benzene molecule and P1 motif in NNM-750, which is fatter and larger than that in site B in NU-1500 (Fig. 5f), demonstrating stronger benzene affinity of NNM-750. This is in line with the experimental results that NNM-750 exhibits significantly improved benzene adsorption performances at low pressure compared with NU-1500.\u003c/p\u003e\n\u003cp\u003eIn summary, in this work, we have demonstrated the successful implementation of \u003cstrong\u003ePSP\u003c/strong\u003e strategy in a series of rigid and lightweight \u003cstrong\u003eacs\u003c/strong\u003e type frameworks based on 6-connected trigonal prismatic linkers as organic vertices. Eight MOFs with four ligand pairs and two metals were made. The introduction of pyridyl ligands with aromatic backbone and the lightweight framework of NNM MOFs has contributed to record-high trace benzene adsorption, which far exceeds previous record at a wide range of pressure. DFT calculations indicated that the use of hexaazaphenalene-based ligand has a much higher binding energy than that of open metal sites. The \u003cstrong\u003ePSP\u003c/strong\u003e on rigid \u003cstrong\u003eacs\u003c/strong\u003e frameworks here significantly broaden the application of \u003cstrong\u003ePSP\u003c/strong\u003e concept and therefore highlight new possibilities for the construction of new \u003cstrong\u003epacs\u003c/strong\u003e MOFs. In addition, the use of large \u0026pi;-conjugated hexaazaphenalene-based ligand in other chemical systems may also have promising applications for the adsorption of aromatic guests\u003c/p\u003e"},{"header":"Method","content":"\u003cp\u003eAll reagents were obtained from commercial sources and used without further purification.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eSynthesis of P1 (HTPH)\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eP1 was synthesized according to the literature\u003csup\u003e20\u003c/sup\u003e. NaC(CN)\u003csub\u003e3\u003c/sub\u003e (0.750g, ~6.6 mmol) and pyridine-4-amidine hydrochloride (4.50 g, ~28 mmol) were ground in an agate mortar to achieve thorough mixing, then transferred to a 23 mL teflon-lined autoclave and then heated at 200 \u003csup\u003eo\u003c/sup\u003eC overnight. After cooled to ambient temperature, 10 wt% HCl solution was added to dissolve the crude product. After filtering undissolved particulates, the solution was neutralized with acetone, and isolated. The dissolution in HCl and neutralization in acetone were repeated twice. The product was isolated and dried overnight under vacuum at 60 \u003csup\u003eo\u003c/sup\u003eC to obtain the final light tan P1 powder.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eSynthesis of NNM-750-Fe [Fe\u003csub\u003e3\u003c/sub\u003eO(L1)(P1)] (single crystal)\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eFeCl\u003csub\u003e3\u003c/sub\u003e\u0026middot;6H\u003csub\u003e2\u003c/sub\u003eO (20 mg, ~0.074 mmol), L1 (10 mg, ~0.01 mmol), P1 (5 mg, ~0.012 mmol), DMF (3.5 mL) and TFA (400 \u0026mu;L) were added in 15 mL glass vial and then ultrasonically treated for 10 min. The vial was placed in 150 \u003csup\u003eo\u003c/sup\u003eC oven for 7 h. Russet triangular prism or hexagonal flake-like NNM-750-Fe crystals were obtained after cooling to room temperature. The yield was about 70% based on the Fe (Experimental: ~27 mg; Theoretical: 38.5 mg). The phase purity was identified by the powder X-ray diffraction.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eSynthesis of NNM-751-Fe [Fe\u003csub\u003e3\u003c/sub\u003eO(L2)(P2)(Cl)\u003csub\u003ex\u003c/sub\u003e(TFA)\u003csub\u003e1-x\u003c/sub\u003e] (single crystal)\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eFeCl\u003csub\u003e3\u003c/sub\u003e\u0026middot;6H\u003csub\u003e2\u003c/sub\u003eO (12 mg, ~0.044 mmol), L2 (10 mg, ~0.007 mmol), P2 (8 mg, ~0.015 mmol), DMF (3.5 mL) and TFA (200 \u0026mu;L) were added in 15 mL glass vial and then ultrasonically treated for 10 min. The vial was placed in 150 \u003csup\u003eo\u003c/sup\u003eC oven for 7 h. Russet triangular or hexagonal flake-like NNM-751-Fe crystals were obtained after cooling to room temperature. The yield was about 70% based on the Fe. The phase purity was identified by the powder X-ray diffraction.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eSynthesis of NNM-752-Fe [Fe\u003csub\u003e3\u003c/sub\u003eO(L2)(P3)(Cl)\u003csub\u003ex\u003c/sub\u003e(TFA)\u003csub\u003e1-x\u003c/sub\u003e] (single crystal)\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eFeCl\u003csub\u003e3\u003c/sub\u003e\u0026middot;6H\u003csub\u003e2\u003c/sub\u003eO (6 mg, ~0.022 mmol), L2 (10 mg, ~0.007 mmol), P3 (4 mg, ~0.007 mmol), DMF (3.5 mL) and TFA (100 \u0026mu;L) were added in 15 mL glass vial and then ultrasonically treated for 10 min. The vial was placed in 150 \u003csup\u003eo\u003c/sup\u003eC oven for 7 h. Russet triangular or hexagonal flake-like NNM-752-Fe crystals were obtained after cooling to room temperature. The yield was about 80% based on the Fe. The phase purity was identified by the powder X-ray diffraction.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eSynthesis of NNM-753-Fe [Fe\u003csub\u003e3\u003c/sub\u003eO(L3)(P1)] (single crystal)\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eFeCl\u003csub\u003e3\u003c/sub\u003e\u0026middot;6H\u003csub\u003e2\u003c/sub\u003eO (8 mg, ~0.030 mmol), L3 (10 mg, ~0.009 mmol), P1 (4 mg, ~0.007 mmol), DMF (3.5 mL) and TFA (400 \u0026mu;L) were added in 15 mL glass vial and then ultrasonically treated for 10 min. The vial was placed in 150 \u003csup\u003eo\u003c/sup\u003eC oven for 7 h. Russet triangular flake-like NNM-753-Fe crystals were obtained after cooling to room temperature. The yield was about 60% based on the Fe. The phase purity was identified by the powder X-ray diffraction.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eSynthesis of NNM-750-Cr [Cr\u003csub\u003e3\u003c/sub\u003eO(L1)(P1)] (powder sample)\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eCr(NO\u003csub\u003e3\u003c/sub\u003e)\u0026middot;9H\u003csub\u003e2\u003c/sub\u003eO (144 mg, ~0.360 mmol), L1 (146 mg, ~0.150 mmol), P1 (48 mg, ~0.119 mmol), H\u003csub\u003e2\u003c/sub\u003eO (2 mL), Py (3 mL) and HF (100 \u0026mu;L) were added in 15 mL glass vial and then ultrasonically treated for 10 min. The mixture was transferred into the teflon-lined stainless-steel autoclave and the vessel was subsequently placed in a 220 \u003csup\u003eo\u003c/sup\u003eC preheated oven for 24 h. After allowing vessel to cool to ambient temperature, the obtained powder sample of NNM-750-Cr was collected by centrifuge under 3000 r/min after washing with DMF and EtOH.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eSynthesis of NNM-751-Cr [Cr\u003csub\u003e3\u003c/sub\u003eO(L2)(P2)(NO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003ex\u003c/sub\u003e(F)\u003csub\u003e1-x\u003c/sub\u003e] (powder sample)\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eCr(NO\u003csub\u003e3\u003c/sub\u003e)\u0026middot;9H\u003csub\u003e2\u003c/sub\u003eO (144 mg, ~0.360 mmol), L2 (215 mg, ~0.150 mmol), P2 (65 mg, ~0.119 mmol), H\u003csub\u003e2\u003c/sub\u003eO (2 mL), Py (3 mL) and HF (100 \u0026mu;L) were added in 15 mL glass vial and then ultrasonically treated for 10 min. The mixture was transferred into the teflon-lined stainless-steel autoclave and the vessel was subsequently placed in a 220 \u003csup\u003eo\u003c/sup\u003eC preheated oven for 24 h. After allowing vessel to cool to ambient temperature, the obtained powder sample of NNM-751-Cr was collected by centrifuge under 3000 r/min after washing with DMF and EtOH.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eSynthesis of NNM-752-Cr [Cr\u003csub\u003e3\u003c/sub\u003eO(L2)(P3)(NO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003ex\u003c/sub\u003e(F)\u003csub\u003e1-x\u003c/sub\u003e] (powder sample)\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eCr(NO\u003csub\u003e3\u003c/sub\u003e)\u0026middot;9H\u003csub\u003e2\u003c/sub\u003eO (144 mg, ~0.360 mmol), L2 (215 mg, ~0.150 mmol), P3 (65 mg, ~0.119 mmol), H\u003csub\u003e2\u003c/sub\u003eO (2 mL), Py (3 mL) and HF (100 \u0026mu;L) were added in 15 mL glass vial and then ultrasonically treated for 10 min. The mixture was transferred into the teflon-lined stainless-steel autoclave and the vessel was subsequently placed in a 220 \u003csup\u003eo\u003c/sup\u003eC preheated oven for 24 h. After allowing vessel to cool to ambient temperature, the obtained powder sample of NNM-752-Cr was collected by centrifuge under 3000 r/min after washing with DMF and EtOH.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eSynthesis of NNM-753-Cr [Cr\u003csub\u003e3\u003c/sub\u003eO(L3)(P1)] (powder sample)\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eCr(NO\u003csub\u003e3\u003c/sub\u003e)\u0026middot;9H\u003csub\u003e2\u003c/sub\u003eO (144 mg, ~0.360 mmol), L3 (158 mg, ~0.148 mmol), P1 (48 mg, ~0.119 mmol), H\u003csub\u003e2\u003c/sub\u003eO (2 mL), Py (3 mL) and HF (100 \u0026mu;L) were added in 15 mL glass vial and then ultrasonically treated for 10 min. The mixture was transferred into the teflon-lined stainless-steel autoclave and the vessel was subsequently placed in a 220 \u003csup\u003eo\u003c/sup\u003eC preheated oven for 24 h. After allowing vessel to cool to ambient temperature, the obtained powder sample of NNM-753-Cr was collected by centrifuge under 3000 r/min after washing with DMF and EtOH.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eSynthesis of NU-1500-Fe (single crystal)\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNU-1500-Fe was synthesized according to the literature\u003csup\u003e11\u003c/sup\u003e. FeCl\u003csub\u003e3\u003c/sub\u003e\u0026middot;6H\u003csub\u003e2\u003c/sub\u003eO (20 mg, ~0.074 mmol), L1 (10 mg, ~0.01 mmol), DMF (3 mL) and TFA (500 \u0026mu;L) were added in 30 mL glass vial and then ultrasonically treated for 10 min. The vial was placed in 150 \u003csup\u003eo\u003c/sup\u003eC oven for 12 h. Pure yellow-orange prismatic block crystals were obtained after cooling to room temperature.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eSynthesis of MIL-88-Fe (powder sample)\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eMIL-88-Fe was synthesized according to the literature\u003csup\u003e50\u003c/sup\u003e. FeCl\u003csub\u003e3\u003c/sub\u003e\u0026middot;6H\u003csub\u003e2\u003c/sub\u003eO (0.187 g, ~0.693 mmol) and terephthalic acid (BDC, 0.126 g, ~0.759 mmol) were dissolved in 15 mL of DMF, and the mixed solution was ultrasonically dispersed for 20 min. Then, the solution was transferred to a 23 mL Tefion-lined reactor at 120 \u003csup\u003eo\u003c/sup\u003eC for 8 h. After cooled to room temperature, the precipitate was separated by centrifugation.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eData availability\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eCrystallographic data for the structures reported in this article have been deposited at the Cambridge Crystallographic Data Centre, under deposition numbers CCDC 2357819 (NNM-750-Fe), 2357820 (NNM-751-Fe), 2357821 (NNM-752-Fe), 2357822 (NNM-753-Fe), 2358289 (NNM-750-Cr), 2357858 (NNM-751-Cr), 2357859 (NNM-752-Cr) and 2357860 (NNM-753-Cr). These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif. The data supporting the findings of this study are available in the Supplementary Information.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe acknowledge the financial support from National Natural Science Foundation of China (Grant No. 22301138 and 22201117), Jiangsu Specially Appointed Professorship, and the startup funding from Nanjing Normal University. We thank Dr. Zhenyi Zhang from Bruker (Beijing) Scientific Technology Co., Ltd. for SCXRD analysis.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eH.J.Y. and C.Z.X. conceived the project. Y.Y.Z., C.Z.X. and H.J.Y. designed and synthesized NNMs. Y.Y.Z. conducted structural characterizations, N\u003csub\u003e2\u003c/sub\u003e adsorption measurements, structural stability measurements and benzene adsorption measurements. Z.F. and H.L.H. performed benzene breakthrough measurements and DFT calculations. Y.X.H. and H.L. synthesized P1 ligand. Q.Y.Q and K.Z. participated in PXRD analysis. H.J.Y. and C.Z.X. wrote the paper, and all the authors contributed to revising it.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAdditional information\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eSupplementary information\u003c/strong\u003e The online version contains supplementary material available at XXXXXX\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eFurukawa, H., Cordova, K. E., O\u0026rsquo;Keeffe, M. \u0026amp; Yaghi, O. M. The Chemistry and Applications of Metal-Organic Frameworks. \u003cem\u003eScience\u003c/em\u003e \u003cstrong\u003e341\u003c/strong\u003e, 1230444, (2013).\u003c/li\u003e\n\u003cli\u003eO\u0026rsquo;Keeffe, M. \u0026amp; Yaghi, O. M. 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Enhancing the peroxidase-like activity of MIL-88B by ligand exchange with polydopamine. \u003cem\u003eDalton Trans.\u003c/em\u003e \u003cstrong\u003e51\u003c/strong\u003e, 2262-2268, (2022).\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"nature-portfolio","isNatureJournal":true,"hasQc":false,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"","title":"Nature Portfolio","twitterHandle":"","acdcEnabled":false,"dfaEnabled":false,"editorialSystem":"ejp","reportingPortfolio":"","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-4530984/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4530984/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe physical adsorbents have shown great promise for the removal of volatile organic compounds (VOCs) such as benzene but they still suffer from low uptake and poor selectivity especially when VOCs are present at trace concentrations. In this work, we demonstrate the successful implementation of pore-space-partition (\u003cstrong\u003ePSP\u003c/strong\u003e) strategy on rigid NU-1500-type metal-organic frameworks (MOFs) containing organic vertices, which has led to a series of MOFs with near-organic backbones (metal mass fraction as low as 5%) and record trace benzene adsorption. The \u003cstrong\u003ePSP\u003c/strong\u003e on rigid \u003cstrong\u003eacs\u003c/strong\u003e MOFs here relies on precise size match and symmetry match between the partitioning ligands and the frameworks. NNM-750-Fe, a structure constructed by partitioning NU-1500 with large π-conjugated hexaazaphenalene-based ligand, exhibits significantly enhanced low-pressure benzene capture than NU-1500-Fe, which far exceeds previous records (42%-69% higher) at a wide pressure range (P/P\u003csub\u003e0\u003c/sub\u003e from 0.003 to 0.01). DFT calculations reveal that the hexaazaphenalene core has a higher benzene affinity than the open metal sites in pristine NU-1500.\u003c/p\u003e","manuscriptTitle":"Pore Space Partition in Rigid Metal-Organic Frameworks Containing Organic Vertices for Trace Benzene Adsorption","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-06-14 10:30:33","doi":"10.21203/rs.3.rs-4530984/v1","editorialEvents":[],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"nature-communications","isNatureJournal":true,"hasQc":false,"allowDirectSubmit":false,"externalIdentity":"NCOMMS","sideBox":"Learn more about [Nature Communications](http://www.nature.com/ncomms/)","snPcode":"","submissionUrl":"https://mts-ncomms.nature.com/","title":"Nature Communications","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"ejp","reportingPortfolio":"Nature Communications","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"61e29cd6-08fb-46bb-9c55-743b936b6a35","owner":[],"postedDate":"June 14th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[{"id":33146630,"name":"Physical sciences/Chemistry/Coordination chemistry"},{"id":33146631,"name":"Physical sciences/Engineering/Chemical engineering"}],"tags":[],"updatedAt":"2024-06-14T10:30:33+00:00","versionOfRecord":[],"versionCreatedAt":"2024-06-14 10:30:33","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-4530984","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4530984","identity":"rs-4530984","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}