The field of metal‐organic frameworks (MOFs) has progressed beyond the design and exploration of powdery and single‐crystalline materials. A current challenge is the fabrication of organized superstructures that can harness the directional properties of the individual constituent MOF crystals. To date, the progress in the fabrication methods of polycrystalline MOF superstructures has led to close‐packed structures with defined crystalline orientation. By controlling the crystalline orientation, the MOF pore channels of the constituent crystals can be aligned along specific directions: these systems possess anisotropic properties including enhanced diffusion along specific directions, preferential orientation of guest species, and protection of functional guests. In this perspective, we discuss the current status of MOF research in the fabrication of oriented polycrystalline superstructures focusing on the specific crystalline directions of orientation. Three methods are examined in detail: the assembly from colloidal MOF solutions, the use of external fields for the alignment of MOF particles, and the heteroepitaxial ceramic‐to‐MOF growth. This perspective aims at promoting the progress of this field of research and inspiring the development of new protocols for the preparation of MOF systems with oriented pore channels, to enable advanced MOF‐based devices with anisotropic properties.

We report the effect of humidity on oriented Cu-MOF films, including the epitaxial transformation of 3D-oriented Cu₂(BDC)₂DABCO into 3D-oriented Cu₂(BDC)₂.

Films and patterns of 3D‐oriented metal‐organic frameworks (MOFs) afford well‐ordered pore structures extending across centimeter‐scale areas. These macroscopic domains of aligned pores are pivotal to enhance diffusion along specific pathways and orient functional guests. The anisotropic properties emerging from this alignment are beneficial for applications in ion conductivity and photonics. However, the structure of 3D‐oriented MOF films and patterns can rapidly degrade under humid and acidic conditions. Thus, more durable 3D‐ordered porous systems are desired for practical applications. Here, oriented porous polymer films and patterns are prepared by using heteroepitaxially oriented N₃‐functionalized MOF films as precursor materials. The film fabrication protocol utilizes an azide–alkyne cycloaddition on the Cu₂(AzBPDC)₂DABCO MOF. The micropatterning protocol exploits the X‐ray sensitivity of azide groups in Cu₂(AzBPDC)₂DABCO, enabling selective degradation in the irradiated areas. The masked regions of the MOF film retain their N₃‐functionality, allowing for subsequent cross‐linking through azide‐alkyne coupling. Subsequent acidic treatment removes the Cu ions from the MOF, yielding porous polymer micro‐patterns. The polymer has high chemical stability and shows an anisotropic fluorescent response. The use of 3D‐oriented MOF systems as precursors for the fabrication of oriented porous polymers will facilitate the progress of optical components for photonic applications.

ISO 14687 sets strict impurity limits for hydrogen used across a wide range of applications, including fuel cell road vehicles (Grade D). Ensuring compliance with these thresholds requires precise analytical methods and certified gas standards for each regulated contaminant. However, preparing and maintaining individual reference standards for routine analysis is resource-intensive. To support the use of multicomponent standards in hydrogen purity control, this study examines the time-dependent stability of commercially prepared standards of ISO 14687 Grade D contaminants in hydrogen matrices. Using ion–molecule reaction, electron-impact mass spectrometry, along with Fourier-transform infrared spectroscopy, results show that several inert and semireactive species, including helium, argon, methane, propane, carbon dioxide, carbon monoxide, carbonyl sulfide, and halogenated compounds, remain stable for over 6 months. Ammonia concentrations stabilized after a 60-day equilibration period of the gas mixture, while oxygen showed inconsistent behavior. Formaldehyde and formic acid exhibited complete signal loss, indicating poor stability in multicomponent mixtures. These findings support the development of reliable multicomponent gas standards and strengthen hydrogen quality control practices under ISO 14687.

Fuel cell electric vehicles (FCEVs) require specific hydrogen purity, as even trace contaminants can degrade proton exchange membrane fuel cells (PEMFCs). While hydrogen quality is monitored along the supply chain according to international standards, potential contamination from in-vehicle materials, such as lubricants and greases, remains largely unexplored. Here, we present a staged testing framework consisting of (i) a rapid pre-screening for formulation stability and (ii) a full qualification pathway to assess lubricant-derived contamination under realistic refueling conditions. Candidate lubricants were exposed to hydrogen in a 700 bar Type IV vessel following an SAE J2601 refueling procedure. Contamination risks were evaluated by optical inspection, particulate matter, and gas analysis, monitoring contaminants specified in ISO 14687:2025 Grade D. The applicability of the framework was demonstrated in practical scenarios. In the pre-screening pathway, a silicone-based formulation fulfilled the 24 h acceptance criteria for formulation stability and was classified as potentially suitable for high-pressure hydrogen tank applications. In contrast, two other lubricants based on silicone and mineral oil exhibited visible changes associated with increased risk of particulate matter release, resulting in a classification of unsuitable. In the full qualification pathway, the fluorinated DuPont^TM MOLYKOTE^® HP-300 Grease was evaluated over 23 days and showed no release of harmful contaminants into the hydrogen gas, leading to the classification of suitable. Collectively, the presented protocols provide a structured basis for screening and qualifying lubricants for high-pressure hydrogen tanks in PEMFC applications, supporting future standardization in hydrogen technologies.

Micropatterning crystalline materials with oriented pores is necessary for the fabrication of devices with anisotropic properties. Crystalline and porous metal-organic frameworks (MOFs) are ideal materials as their chemical and structural mutability enables precise tuning of functional properties for applications ranging from microelectronics to photonics. Herein, we design a patternable oriented MOF film: by using a photomask under X-ray exposure, the MOF film decomposes in the irradiated areas, remaining intact in the unexposed regions. The MOF film acts simultaneously as a resist and as functional porous material. While the heteroepitaxial growth from aligned Cu(OH)2 nanobelts is used to deposit oriented MOF films, the sensitivity to radiation is achieved by integrating a brominated dicarboxylic ligand (Br2BDC) into a copper-based MOF Cu2L2DABCO (L=BDC/Br2BDC). The lithographed samples act as a diffraction grating upon irradiation with a laser, thus confirming the quality of the extended MOF micropattern. Furthermore, the oriented MOF patterns are functionalized with fluorescent dyes. As a result, by rotating the polarization angle of the laser excitation, we demonstrate the alignment of the dye in the MOF. By controlling the functional response to light, this MOF patterning protocol could be used for the microfabrication of optical components for photonic devices.