Oil contaminated water is a global issue, decreasing the quality of water sources and is posing a threat to the health of humans and many ecosystems. The utilization of industrial level strategies is limited mainly due to their complex and time-consuming processing. Considering this, we choose materials for separating oils from water based on their ease of handling and good performance. However, high surface area porous materials, such as linens, zeolites, cotton, etc., offer low efficiency for oil/water separation. Special wettability is the most promising property of materials and is helpful for oil–water separation. Metal–organic frameworks (MOFs), a class of highly tunable porous structures of metal clusters/ions and multidentate organic ligands, offer exciting prospects for various applications. The unique tunability of the structure and properties of these materials can endow them with special wettability for the treatment of oily water. This review focuses on hydrophobic–oleophilic, hydrophilic–underwater oleophobic and switchable wettability MOFs and their implementation as oil/water separating materials. We classify different MOF-based materials as filtration materials, absorbents or adsorbents based on the methodology they are used in for separating oil/water mixtures and emulsions. We discuss different subclasses of MOF-based filtration, absorbent and adsorbent materials and summarize recent developments in their oil/water separation applications. Finally, we end our discussion by critically analyzing the importance of these MOFs for separating oils from water and highlighting potential future directions for achieving improved performance.

Superhydrophobic MOF-nanosheets assembled on the outside of an aqueous droplet form ‘liquid marbles’. A facile mechanochemical-based synthesis followed by ultrasonication was used to prepare two-dimensional superhydrophobic–oleophilic MOF nanosheets of a Co²⁺-based zeolitic imidazolate framework, namely ZIF-9-III ([Co₄(bIm)₁₆] with bIm⁻ = benzimidazolate). The resulting ZIF-9-III showed excellent hydrophobicity (advancing water contact angle of 144°) and oleophilicity (oil contact angle of ≈0°). The superhydrophobic behavior originated from its predominant outer (002) surface, which featured nanoscale corrugation caused by the exposed benzimidazole groups. This behavior was corroborated by inverse gas chromatography measurements to determine the surface energies of bulk exfoliated 2D ZIF-9-III nanosheets and 3D ZIF-9-I. Taking advantage of the unique surface properties, including low surface energy and good moisture stability, we prepared ZIF-9-III@PVDF (PVDF = polyvinylidene fluoride) membranes following the non-solvent induced phase inversion (NIPS) process. The resulting membranes were exploited in real-time oil/water separation and featured remarkably high adsorption capacity and anti-staining properties. Therefore, this work opens the door to developing new superhydrophobic MOF-based composite materials with permeant porosity, which may enable applications in self-cleaning membranes for oil–water separation.

A unique feature of flexible metal–organic frameworks (MOFs) is their ability to respond dynamically towards molecular stimuli by structural transitions, resulting in pore-opening and closing processes. One of the most intriguing modes is the “gating”, where the material transforms from the dense to the porous state. The conditions required for the solid phase structural transition are controlled by the kinetic barriers, including nucleation of the new phase commencing on the crystallite's outer surface. Thus, surface deformation may influence the nucleation, enabling deliberate tailoring of the responsivity. In the present contribution, we investigate how chemical surface treatments (surface deformation) affect the gate opening characteristics of a typical representative of gate pressure MOFs, DUT-8(Ni) ([Ni₂(ndc)₂(dabco)]_n, ndc = 2,6-naphthalenedicarboxylate, dabco = 1,4-diazabicyclo[2.2.2]octane). A combination of various complementary advanced characterization techniques, such as NMR, nanoFTIR, terahertz, in situ XPS, in situ EPR spectroscopies, and inverse gas chromatography, are applied to unravel the changes in surface energy and mechanism of surface deformation.

Anchoring single metal atoms on suitable substrates is a convenient route towards materials with unique electronic and magnetic properties exploitable in a wide range of applications including sensors, data storage, and single atom catalysis (SAC). Among a large portfolio of available substrates, carbon-based materials derived from graphene and its derivatives have received growing concern due to their high affinity to metals combined with biocompatibility, low toxicity, and accessibility. Cyanographene (GCN) as highly functionalized graphene containing homogeneously distributed nitrile groups perpendicular to the surface offers exceptionally favourable arrangement for anchoring metal atoms enabling efficient charge exchange between the metal and the substrate. However, the binding characteristics of metal species can be significantly affected by the coordination effects. Here we employed density functional theory (DFT) calculations to analyse the role of coordination in the binding of late 3d cations (Fe²⁺, Fe³⁺, Co²⁺, Ni²⁺, Cu²⁺, Cu⁺, and Zn²⁺) to GCN in aqueous solutions. The inspection of several plausible coordination types revealed the most favourable arrangements. Among the studied species, copper cations were found to be the most tightly bonded to GCN, which was also confirmed by the X-ray photoelectron spectroscopy (XPS), atomic absorption spectroscopy (AAS), and isothermal titration calorimetry (ITC) measurements. In general, the inclusion of coordination effects significantly reduced the binding affinities predicted by implicit solvation models. Clearly, to build-up reliable models of SAC architectures in the environments enabling the formation of a coordination sphere, such effects need to be properly taken into account.

Background/Objectives: Crystallization is a key process in the manufacturing of active pharmaceutical ingredients (APIs), as it significantly affects the physical and chemical properties of the final product. Nicergoline, a clinically relevant ergot derivative, was chosen as a model compound to investigate how different crystallization strategies affect particle attributes. The objective of this study was to compare controlled and uncontrolled crystallization techniques and evaluate their impact on the physicochemical properties of nicergoline. Methods: Nicergoline was crystallized using controlled methods, including sonication-induced and seeding-induced crystallization, and uncontrolled methods, namely cubic and linear cooling, as well as acetone evaporation. The resulting powders were characterized by using a range of physicochemical techniques to assess particle morphology, size distribution, agglomeration behavior, and surface properties. Results: Uncontrolled crystallization methods produced particles prone to agglomeration, resulting in a broader particle size distribution ranging from 8 to 720 µm and heterogeneous surface characteristics. In contrast, controlled crystallization generated more uniform particles with reduced agglomeration and narrower particle size distributions. Among the evaluated methods, sonocrystallization provided the most effective control over particle size and morphology, demonstrated by a narrow size distribution ranging from 16 to 39 µm which correlated with improved flowability and surface energy. Conclusions: The study demonstrates that the choice of crystallization method significantly influences the structural and physicochemical properties of nicergoline. These findings highlight the importance of method selection for tailoring API properties to enhance downstream processing and product quality.