•Recent progress focusing on metal–organic frameworks for supercapacitor applications is summarized.•MOFs can be utilized as either the electrode materials or the precusors for electrode materials ...due to their high-tunability.•The recyclable MOF-hydrolyzing strategy is particularly introduced in this manuscript. The expensive ligands can be recycled, and the synthesis costs are drastically reduced.
Supercapacitors are important energy storage devices due to its fast charging/discharging features and long cycle life. Design and fabrication of superior supercapacitor electrodes is of significance to the improvement of the overall performances of a device. Metal-organic frameworks (MOFs) have been widely reported for supercapacitor applications due to their high-tunability, including favorable porous properties, tunable chemical compositions, controllable crystal structures, and adjustable geometry morphologies. In this review, the recent reports focusing on MOF-based supercapacitor applications are elaborated. Particularly, the recyclable MOF-hydrolyzing strategy is introduced, during which the organic ligands can be recollected to drastically reduce the costs. Furthermore, challenges and perspectives of MOFs for supercapacitor electrode applications are also summarized.
•The application of isoreticular chemistry in MOF structure design, including microstructure design, pore size tailoring, secondary building unit modification, post-synthesis modification, and ...cooperative regulation are summarized and highlight.•The adsorption/separation function-oriented MOF structure design and high-throughput screening process are summarized. Based on isoreticular chemistry design and optimized high-performance MOF adsorbents and membranes, we are committed to exploring an energy-intensive and environmentally friendly alternative separation route, and strive to achieve efficient separation of hydrogen, carbon dioxide, natural gas, and petroleum-based platform compounds.
Precise control of the pore size and environment of metal–organic framework (MOF) is a necessary condition for achieving high performance of gas adsorption and separation. After nearly two decades of development, the synthesis of MOF materials has gradually evolved from exploration and trial to precise-design, including function-oriented microstructure design and optimization, pore size tailoring, and secondary building unit (SBU) modification. The unique pore environments of MOF materials enable their advantages in gas adsorption and separation applications. In addition, the introduction of isoreticular chemistry within MOFs (with the same framework structure and different chemical components) provides opportunities for improving gas adsorption and separation performance. Isoreticular chemistry gives MOFs more functions to promote specific binding or sieving with gas molecules. Furthermore, MOF-based adsorbents and separation membranes exhibit superior separation performance in many industrial gas purification processes. In this review, we summarized and highlight the application of isoreticular chemistry in MOF structure design, including microstructure design, pore size tailoring, SBU modification, post-synthesis modification, and cooperative regulation. The gas adsorption and separation performances are improved through pore size and environment optimization. In addition, we also summarized the adsorption/separation function-oriented MOF structure design and high-throughput screening process. Based on isoreticular chemistry design and optimized high-performance MOF adsorbents and separation membranes, an energy-intensive and environmentally friendly alternative separation route is explored to achieve efficient separation of hydrogen, carbon dioxide, natural gas, and petroleum-based compounds. Finally, we provided an outlook based on prospect developments of isoreticular chemistry within MOFs for gas storage and separation.
Gas separation is one of the most critical and challenging steps for industrial processes, and metal-organic framework (MOF) membranes are potential candidates for this application. This review ...mainly focuses on the recent advances in improving the performance of MOF membranes, involving the issues faced with MOF designation and growth for practical applications. First, we discussed three strategies for permeability and selectivity enhancement of MOF membranes, in terms of obtaining ultra-thin two-dimensional (2D) MOF nanosheets, fine-tuning the pore size of the MOF framework and integrating with other species. Second, we reviewed the recent potential resolutions to the problems of MOF membranes for future practical applications including scale-up preparation and stability improvement. Finally, we summarized our work by providing some general conclusions on the state-of-the-art and an outlook on some development directions of molecule-sieving membranes.
In this review, we summarized the recent advances in improving the gas separation performance of MOF membranes and the issues faced with MOF membranes in terms of designation and growth for their practical applications.
Flexible metal-organic frameworks (MOFs) have gradually attracted much attention due to their reversible structural changes and flexible structural responses. The basic research of flexible MOFs is ...to study their dynamic responses under different external stimuli and translate the responses into applications. Most research studies on flexible MOFs focus on gas storage and separation, but lack a systematic summary. Here, we review the development of flexible MOFs, the structural transformation under the external effects of temperature, pressure, and guest molecules, and their applications in gas storage and separation. Microporous MOFs with flexible structures provide unique opportunities for fine-tuning their performance because the pore shape and size can be controlled by external stimuli. The characteristics of breathing phenomena and large specific surface area make flexible MOFs suitable candidates for gas storage and separation. Finally, the application prospects of flexible MOFs are reported.
Dynamic response of flexible MOF for gas storage and separation.
Adsorptive separation of acetylene (C2H2) from carbon dioxide (CO2) promises a practical way to produce high-purity C2H2 required for industrial applications. However, challenges exist in the pore ...environment engineering of porous materials to recognize two molecules due to their similar molecular sizes and physical properties. Herein, we report a strategy to optimize pore environments of multivariate metal–organic frameworks (MOFs) for efficient C2H2/CO2 separation by tuning metal components, functionalized linkers, and terminal ligands. The optimized material UPC-200(Al)-F-BIM, constructed from Al3+ clusters, fluorine-functionalized organic linkers, and benzimidazole terminal ligands, demonstrated the highest separation efficiency (C2H2/CO2 uptake ratio of 2.6) and highest C2H2 productivity among UPC-200 systems. Experimental and computational studies revealed the contribution of small pore size and polar functional groups on the C2H2/CO2 selectivity and indicated the practical C2H2/CO2 separation of UPC-200(Al)-F-BIM.
Isoreticular functionalization is a well‐elucidated strategy for pore environment tuning and the basis of gas separation performance in extended frameworks. The extension of this approach to discrete ...porous molecules such as metal‐organic cages (MOCs) is conceptually straightforward but hindered by synthetic complications, especially stability concerns. We report the successful isoreticular functionalization of a zirconium MOC with tetrazole moiety by bottom‐up synthesis. The title compound (ZrT‐1‐tetrazol) shows promising C2H2/CO2 and C2H2/C2H4 separation performance, as demonstrated by adsorption isotherms, breakthrough experiments, and density functional theory calculations. The design analogy between MOFs and highly stable MOCs may guide the synthesis of novel porous materials for challenging separation applications.
We report the use of isoreticular chemistry to synthesize a tetrazole‐functionalized metal‐organic cage (ZrT‐1‐tetrazol) with the same structure of ZrT‐1 and ZrT‐1‐NH2. The adsorption capacity of ZrT‐1‐tetrazol for C2H2 increases by 130 % (298 K) compared with ZrT‐1‐NH2, and it exhibits promising C2H2/CO2 and C2H2/C2H4 separation performance.
Five lanthanide metal-organic frameworks, Ln(L)(H sub(2)O)(NMP).1.5H sub(2)O (Ln = Ce (1), Pr (2); H sub(3)L = 1,3,5-tris(4-carboxyphenyl-1-ylmethyl)-2,4,6-trimethylbenzene), and Ln sub(2)(L) sub(2) ...(H sub(2)O) sub(3).2H sub(2)O (Ln = Eu (3), Tm (4), Yb (5)), have been synthesized and characterized. Complexes 1-5 exhibit similar 1D channels through the linkage of Ln-carboxylate chains with the backbones of H sub(3)L ligands. The channels for complexes 1 and 2 are occupied by coordinated NMP molecules. 3 shows potential application for the luminescence sensing of small organic molecules. Moreover, 5 exhibits selective adsorption of CO sub(2) over N sub(2) and CH sub(4) and catalytic activities toward the cyanosilylation reaction.
We report the development of a new type of organic semiconductor gas sensor based on a porphyrin-based hydrogen-bonded organic framework (HOF). Owing to the orderly porous structures, the decoration ...with rich amino sites and the n-type semiconductor nature, this HOF-based sensor exhibits selective NO2 sensing performance with ultra-fast response/recovery rates (17.6 s/15.4 s over 100 ppb) and a limit of detection lower than 40 ppb, together with high sensitivity, good reproducibility, and long-term stability at room temperature. This study demonstrates that HOF-based materials have potential application prospects in gas sensing, thereby offering a new way of thinking for the design and development of sensors.
Ordered and flexible porous frameworks with solution processability are highly desirable to fabricate continuous and large‐scale membranes for the efficient gas separation. Herein, the first ...microporous hydrogen‐bonded organic framework (HOF) membrane has been fabricated by an optimized solution‐processing technique. The framework exhibits the superior stability because of the abundant hydrogen bonds and strong π–π interactions. Thanks to the flexible HOF structure, the membrane possesses the unprecedented pressure‐responsive H2/N2 separation performance. Furthermore, the scratched membrane can be healed by the treatment of solvent vapor, achieving the recovery of separation performance.
Press to separate: A hydrogen‐bonded organic framework membrane has been fabricated by simple solution‐processing techniques. It shows pressure‐responsive gas separation performance.
Hydrogen-bonded organic frameworks (HOFs), similar to their MOF analogues, exhibit great potential in proton conduction applications. Herein, a porous HOF namely (NiH
4
TPPP)(Me
2
NH
2
)
4
(DMF)(H
2
...O)
4
(UPC-H5) was synthesized from phosphonate-based porphyrinato nickel (NiH
8
TPPP), and its proton conductivity is regulated through a two-step guest change. Firstly, immersing UPC-H5 in CH
2
Cl
2
to exchange lattice solvent molecules for 24 h followed by heating under vacuum afforded the lattice solvent molecule-free HOF (NiH
4
TPPP)(Me
2
NH
2
)
4
(UPC-H5a) with the pristine framework still retained. Secondly, exposing UPC-H5a to vapors of 25% aqueous ammonia for 24 h at room temperature gave a new derivative UPC-H5a@NH
3
·H
2
O with the molecular formula (NiH
4
TPPP)(Me
2
NH
2
)
2
(NH
4
)
2
(H
2
O)
4
according to elemental and thermal analyses. At 30 °C and 95% R.H., the proton conductivity of UPC-H5, UPC-H5a, and UPC-H5a@NH
3
·H
2
O amounts to 5.59 × 10
−4
, 7.00 × 10
−3
, and 1.47 × 10
−2
S cm
−1
, respectively, which increases to 1.85 × 10
−3
, 3.42 × 10
−2
, and 1.59 × 10
−1
S cm
−1
at 80 °C and 99% R.H., clearly showing the effect of guest regulation on the proton conductivity of the HOF-based materials. In addition, this result is also helpful towards understanding the important role of guests in the formation of their proton conduction pathways.
A porous porphyrin-based hydrogen-bonded organic framework (HOF) was constructed, and its proton conductivity was improved through a two-step guest-tuned strategy. After regulation, the proton conductivity of the HOF reaches 1.59 × 10
−1
S cm
−1
at 80 °C and 99% RH.
