Research progress on the substrate for metal-organic framework(MOF) membrane growth for separation

During the last decade, metal-organic frameworks(MOFs) have been applied in various fields due to their unique chemical and functional advantages. One of the widespread research hotspots is MOF-based membranes for separations, specifically continuous defect-free MOF membranes, which are usually grown on porous substrates. The substrate not only serves as the MOF layer support but also has a great influence on the membrane fabrication process and the final separation performance of the resultant membrane. In this review, we mainly introduce the progress focused on the substrates for MOF membranes fabrication. The substrate modifications and seeding methods aimed at synthesizing highquality MOF membranes are also summarized systematically.

A Rapid-Ab/Desorption and Portable Photothermal MIL- 101(Cr) Nanofibrous Composite Membrane Fabricated by Spray-Electrospinning for Atmosphere Water Harvesting

MIL-101(Cr)is a promising moisture absorbent for solar-driven water harvesting from moisture to tackle the worldwide water shortage issue.However,the MIL-101(Cr)powder suffers from a long ab/desorption cycle due to the crystal aggregation caused by its inherent powder properties.Here,we demonstrate a MIL-101(Cr)nanofibrous composite membrane with a nanofibrous matrix where MIL-101(Cr)is monodisperse in the 3D porous nanofibrous matrix through a simple spray-electrospinning strategy.The continuous porous nanofibrous matrix not only offers sufficient sites for MIL-101(Cr)loading but also provides rapid moisture transport channels,resulting in a super-rapid ab/desorption duration of 50 min(including an absorption process for 40 min and a desorption process for 10 min)and multicycle daily water production of 15.9 L kg^(−1) d^(−1).Besides,the MIL-101(Cr)nanofibrous composite membrane establishes a high solar absorption of 92.8%,and excellent photothermal conversion with the surface temperature of 70.7°C under one-sun irradiation.In addition,the MIL-101(Cr)nanofibrous composite membrane shows excellent potential for practical application due to its flexibility,portability,and use stability.This work provides a new perspective of shortening MOF ab/desorption duration by introducing a porous nanofibrous matrix to improve the specific water production for the solar-driven ab/desorption water harvesting technique.

高度灵活可控的多孔MOF膜用于高效药物释放

具有生物力学和生化活性的敷料在伤口护理和皮肤组织再生中起着至关重要的作用.然而,机械失配和药物释放管理所涉及的问题限制了当前敷料的有效使用.在本工作中,我们报道了一种简单的策略,即采用聚偏二氟乙烯(PVDF)作为底物,通过嵌入不同尺寸的沸石咪唑酸盐框架(ZIF-8)种子,以推动具有均匀蜂窝结构的高柔性金属有机框架(MOF)复合膜的受控生长,用于药物负载和释放.以嵌入的种子为控制中心,形成的多孔膜具有约0.7-3μm的宽孔隙.这种可调节的微尺度孔与ZIF-8中的固有纳米孔不仅可以有效地提高抗炎类药物的负载(姜黄素,CCM),而且还能够快速并可控地释放药物,大大提高了抗菌活性,同时促进细胞生长.其中,在40 nm种子上生长的0.7μm多孔膜的表现优于其他蜂窝膜,与2μm多孔膜(相当于裸PVDF基质)相比,细胞增殖能力提高了约2倍,针对金黄色葡萄球菌(S.aureus)和大肠杆菌(E.coli)的抗菌活性分别提高了5倍和2.4倍,是基底抗菌活性的5倍,这是因为这种最佳孔几何结构具有CCM和Zn2+释放特性的平衡效应.这种可控分层孔阵列膜的独特性质有望真正用于伤口愈合,同时也为生物医学设计提供了新的指导.

Interfacially stable MOF nanosheet membrane with tailored nanochannels for ultrafast and thermo-responsive nanofiltration

Two-dimensional nanosheet membranes with responsive nanochannels are appealing for controlled mass transfer/separation,but limited by everchanging thicknesses arising from unstable interfaces.Herein,an interfacially stable,thermo-responsive nanosheet membrane is assembled from twin-chain stabilized metal-organic framework(MOF)nanosheets,which function via two cyclic amide-bearing polymers,thermo-responsive poly(N-vinyl caprolactam)(PVCL)for adjusting channel size,and non-responsive polyvinylpyrrolidone for supporting constant interlayer distance.Owing to the microporosity of MOF nanosheets and controllable interface wettability,the hybrid membrane demonstrates both superior separation performance and stable thermo-responsiveness.Scattering and correlation spectroscopic analyses further corroborate the respective roles of the two polymers and reveal the microenvironment changes of nanochannels are motivated by the dehydration of PVCL chains.

Inorganic microporous membranes for hydrogen separation:Challenges and solutions

Porous membrane separation is a competitive hydrogen purification technology due to the advantages of environmental friendliness,energy-saving,simple operation,and low cost.Benefiting from the booming development of materials science and chemical science,great progress has been made in H_(2) separation with porous membranes.This review focuses on the latest advances in the design and fabrication of H_(2) separation inorganic microporous membranes,with emphasis on the synthetic strategies to achieve structural integrity,continuity and stability.This review starts with a brief introduction to the membrane separation mechanisms,followed by an elaboration on the synthetic challenges and corresponding solutions of various high-performance inorganic microporous membranes based on zeolites,silica,carbon,and metal-organic frameworks(MOFs).At last,by highlighting the prospects of ultrathin two-dimensional(2D)porous membranes,we wish to shed some light on the further development of new materials and membranes for highly efficient hydrogen separation.

Nafion-threaded MOF laminar membrane with efficient and stable transfer channels towards highly enhanced proton conduction

Porous laminar membranes hold great promise to realize ultrafast ion transfer if efficient and stable transfer channels are constructed in vertical direction.Here,metal-organic framework(MOF)nanosheets bearing imidazole molecules in the pores were designed as building blocks to assemble free-standing MOF laminar membrane.Then,Nafion chains were threaded into the pores induced by electrostatic attraction from imidazole molecules by slowly filtering dilute Nafion solution.We demonstrate that the threaded Nafion chains lock adjacent MOF nanosheets,affording highly enhanced structural stability to the resultant laminar membrane with almost no water swelling.Significantly,abundant acid-base pairs are formed in the pores along Nafion chains,working as efficient,continuous conduction pathways in vertical direction.Proton conductivities as high as 110 and 46 mS·cm^(-1)are obtained by this membrane under 100%and 40%relative humidity(RH),respectively,which are two orders of magnitude higher than that of pristine MOF membrane.The conductivity under low humidity(40%RH)is even over 2 times higher than that of commercial Nafion membrane,generating the maximum power density of 1,100 mW·cm^(-2)in hydrogen fuel cell(vs.291 mW·cm^(-2)of Nafion membrane).Besides,the influence of water state on proton transfer in confined space is investigated in detail.

ZIF-L membrane with a membrane-interlocked-support composite architecture for H/CO separation

Metal–organic framework(MOF)membranes hold great promise in energy-efficient chemical separations.The outstanding challenges of the microstructural design stem from(1)thinning of membranes to immensely reduce the mass-transfer resistance(for high permeances);(2)tuning of orientation to optimize the selective transport of gas molecules,and(3)reinforcement of intercrystalline structure to subside leakage through defective gaps(for high selectivity).Here,we propose the ZIF-L membrane that is completely confined into the voids of the alumina support through an interfacial assembly process,producing an appealing membrane-interlocked-support(MIS)composite architecture that meets the requirements of the microstructural design of MOF membranes.Consequently,the membranes show average H2 permeances of above 4000 GPU and H_(2)/CO_(2) separation factor(SF)of above 200,representing record-high separation performances of ZIF-L membranes and falling into the industrial target zone(H_(2) permeance>1000 GPU and H_(2)/CO_(2) SF>60).Furthermore,the ZIF-L membrane possessing the MIS composite architecture that is established with alumina particles as scaffolds shows mechanical stability,scraped repeatedly by a piece of silicon rubber causing no selectivity loss.