Solution Shearing of Zirconium (Zr)-Based Metal-Organic Frameworks NU-901 and MOF-525 Thin Films for Electrocatalytic Reduction Applications

Solution shearing, a meniscus-guided coating process, can create large-area metal-organic framework (MOF) thin films rapidly, which can lead to the formation of uniform membranes for separations or thin films for sensing and catalysis applications. Although previous work has shown that solution shearing can render MOF thin films, examples have been limited to a few prototypical systems, such as HKUST-1, Cu-HHTP, and UiO-66. Here, we expand on the applicability of solution shearing by making thin films of NU-901, a zirconium-based MOF. We study how the NU-901 thin film properties (i.e., crystallinity, surface coverage, and thickness) can be controlled as a function of substrate temperature and linker concentration. High fractional surface coverage of small-area (∼1 cm2) NU-901 thin films (0.88 ± 0.06) is achieved on a glass substrate for all conditions after one blade pass, while a low to moderate fractional surface coverage (0.73 ± 0.18) is obtained for large-area (∼5 cm2) NU-901 thin films. The crystallinity of NU-901 crystals increases with temperature and decreases with linker concentration. On the other hand, the adjusted thickness of NU-901 thin films increases with both increasing temperature and linker concentration. We also extend the solution shearing technique to synthesize MOF-525 thin films on a transparent conductive oxide that are useful for electrocatalysis. We show that Fe-metalated MOF-525 films can reduce CO2 to CO, which has implications for CO2 capture and utilization. The demonstration of thin film formation of NU-901 and MOF-525 using solution shearing on a wide range of substrates will be highly useful for implementing these MOFs in sensing and catalytic applications.

Structural Regulation of Two Polyoxometalate-Based Metal-Organic Frameworks for the Heterogeneous Catalysis of Quinazolinones

Two dimeric {ε-Zn₄PMo₁₂}-based metal-organic frameworks (MOFs), [ε-PMo₈^VMo₄^VIO₃₄(OH)₆Zn₄][LO] (SDUT-21, LO = [5-((4'-carboxybenzyl)oxy)isophthalic acid]) and [TBA]₃[ε-PMo₈^VMo₄^VIO₃₇(OH)₃Zn₄][LN] (SDUT-22, TBA⁺ = tetrabutylammonium ion, LN = [5-((4-carboxybenzyl)imino)isophthalic acid]), combining the advantages of polyoxometalates (POMs) and MOFs, were synthesized by the one-pot assembly strategy. The dimeric {ε-Zn₄PMo₁₂} units act as nodes that are linked by the flexible ligands and extended into two- or three-dimensional frameworks. The cyclic voltammetry and proton conductivity measurements of SDUT-21 and SDUT-22 were performed and indicated the high electron and proton transfer abilities. These materials also e xhibited the catalytic performance for the synthesis of quinazolinones in the heterogeneous state, and the different binding capacities toward the substrates caused the catalytic activity of SDUT-21 to be higher than that of SDUT-22 under the same conditions. In addition, the used catalysts could be readily recovered for five successive cycles and maintained high catalytic efficiency.

Two Multiresponsive Luminescent Zn-MOFs for the Detection of Different Chemicals in Simulated Urine and Antibiotics/Cations/Anions in Aqueous Media

Two Zn-MOFs, namely, {[Zn(L)_0.5(bpea)]·0.5H₂O·0.5DMF}_n [LCU-113 (for Liaocheng University)] and {[Zn(L)_0.5(ibpt)]·H₂O·DMF}_n (LCU-114), were synthesized based on flexible tetracarboxylic acid 1,3-bis(3,5-dicarboxyphenoxy)benzene (H₄L) and different N-ligands [bpea = 1,2-dipyridyl ethane; ibpt = 3-(4'-imidazolobenzene)-5-(pyridine-4'-yl)-1,2,4-triazole]. LCU-113 and LCU-114 possess twofold interpenetrating three-dimensional pillared layer structures, in which a two-dimensional layer formed by carboxylic acid and Zn²⁺ ions was pillared by bpea and ibpt, respectively. The two complexes show high water stability and high luminescence sensing performance toward organic solvents, ions, and antibiotics, as well as chemicals, in simulated urine. The investigation showed that (1) LCU-113 and LCU-114 could detect uric acid (UA, 2,6,8-trihydroxypurine, metabolite of purine) and p-aminophenol (PAP, biomarker of phenamine) in simulated urine by luminescence quenching, respectively, and (2) luminescence quenching of LCU-113 and LCU-114 occurred in aqueous solutions of nitrofurazone (NZF), Fe³⁺, and CrO₄^2-/Cr₂O₇^2-. All the above detections have excellent anti-interference ability and recyclability. The luminescence mechanism analysis indicates that weak interactions between the framework structures and the target analytes as well as the energy competition (inner filter effect) play an important role in sensing the above analytes. The practical application for monitoring NZF/Fe³⁺ in water samples was also tested.

Recent progress on porous MOFs for process-efficient hydrocarbon separation, luminescent sensing, and information encryption

Metal-organic frameworks (MOFs), as an emerging class of porous materials, excel in designability, regulatability, and modifiability in terms of their composition, topology, pore size, and surface chemistry, thus affording a huge potential for addressing environment and energy-related challenges. In particular, MOFs can be applied as porous adsorbents for the purification of industrially important hydrocarbons through certain process-efficient separation schemes based on selectivity-reversed adsorption and multicomponent separation. Moreover, the vast combination possibilities and controllable and engineerable luminescent units of MOFs make them a versatile platform to develop functionally tailored materials for luminescent sensing and optical data encryption. In this feature article, we summarize the recent progress in the use of porous MOFs for the separation and purification of acetylene (C₂H₂) and ethylene (C₂H₄) based on selectivity-reversed adsorption and multicomponent separation strategies. Moreover, we highlight the advances over the past three years in the field of MOF-based luminescent materials for thermometry, turn-on sensing, and information encryption.

Stable bifunctional ZnII-based sensor toward acetylacetone and L-histidine by fluorescence red shift and turn-on effect

A new coordination polymer [Zn(bbip)(NH2-BDC)]n (JXUST-15, bbip = 2,6-bis(benzimidazol-1-yl)pyridine and NH2-H2BDC = 2-aminoterephthalic acid) has been synthesized by mixed ligand strategy. The structure analysis shows that JXUST-15 takes a two-dimensional...

Lanthanide-based metal-organic framework materials as bifunctional fluorescence sensors toward acetylacetone and aspartic acid

A family of novel lanthanide-based metal-organic frameworks (Ln-MOFs) with bifunctional fluorescence sensing, namely {[(CH3)2NH2]5[Ln5(TBAPy)5]•solvent}n (Ln = Gd (1), Tb (2), and Dy (3), H4TBAPy = 1,3,5,7-tetra(4-carboxybenzene)pyrene), have been synthesized and...

Various carboxylates induced eight Zn(ii)/Cd(ii) coordination polymers with fluorescence sensing activities for Fe(iii), Cr(vi) and oxytetracycline

Eight new Zn(ii)/Cd(ii) coordination polymers constructed from a naphthalene-amide-pyridyl ligand and various carboxylates were synthesized and characterized, which show multifunctional fluorescence responses for cations, anions and antibiotics.

Construction of high-nuclear 4p–4f heterometallic {Ln11Ge12} cluster-organic frameworks with high-sensitivity luminescence sensing of Fe3+ in aqueous solution

The [Pr₁₁Ge₁₂] 4p–4f cluster-organic framework shows highly selective and sensitive sensing of Fe³⁺ in aqueous solution.

Two anthracene chromophore based metal–organic frameworks for gas adsorption and promising nitro aromatic sensing

Two novel metal–organic frameworks (MOFs) have been synthesized under solvothermal conditions. Studies on luminescence sensing show 1 and 2 are highly selective and recyclable in the detection of nitroaromatic explosives, especially for TNP.