Pantelis N. Trikalitis

We present MOFSynth-ADV, an advanced iteration of the MOFSynth tool designed to evaluate the synthetic feasibility of Metal-Organic Frameworks (MOFs). By integrating the Atomic Simulation Environment (ASE) to leverage extended tight-binding (xTB) and machine learning interatomic potential (MLIP) calculations, MOFSynth-ADV achieves geometry optimization and energy evaluations with significantly higher accuracy than classical force field approaches. Crucially, this update eliminates reliance on proprietary software, delivering a fully open-source solution optimized for high-throughput screening. Performance benchmarks reveal that the xTB module reduces unconverged cases by 73% while decreasing computational time by 13%, with MLIPs (specifically MACE-OFF) yielding comparable improvements. Validated against a benchmark set of experimentally reported MOFs, MOFSynth-ADV demonstrates superior structural and energetic prediction quality, effectively capturing the subtle chemical interactions essential for accurate synthesis prediction. Fast, modular, and easily deployable, this upgraded framework establishes a robust foundation for future machine learning and quantum-classical hybrid workflows in MOF discovery.

The rational design of ultraporous metal-organic frameworks (MOFs) with hierarchical pore systems is of great significance but remains highly challenging. MOFs based on the reo-e or red topologies offer such pore architectures through face-shared cuboidal, cuboctahedral, and rhombicuboctahedral cages. Although hypothesized and computationally explored over the past two decades, these solids had not been experimentally realized. Here, we report the first MOFs based on the long-awaited red-a net, denoted as M-red-MOF-1 (M = Fe, Cr). Combining the nearly square yet rectangularly connected 4-c organic linker 4,4',″,4‴-([1,1':4',1″-terphenyl]-3,3'',5,5''-tetrayltetrakis(ethyne-2,1-diyl))tetrabenzoic acid, denoted as H₄TCEPT, with FeCl₃·6H₂O under solvothermal conditions yielded Fe-red-MOF-1 as cubic-like single crystals. Extensive characterization using SCXRD, PXRD, SEM, TEM, gas sorption, TGA, and in-silico structure modeling, confirmed the red-a topology. Argon sorption at 87 K revealed three distinct S-type steps, consistent with the hierarchical pore network and demonstrated an ultrahigh pore volume (3.56 cm³ g^-1) and BET area (5081 m² g^-1). Owing to its hierarchical porosity, Fe-red-MOF-1 exhibits excellent hydrogen storage performance with high gravimetric (13.5 wt %) and volumetric (39.5 g·L^-1) working capacities under temperature and pressure swing conditions (77 K/100 bar → 160 K/5 bar), placing it among the top-performing MOFs. The isostructural Cr-red-MOF-1, obtained postsynthetically, showed a remarkable water uptake of 2.81 g g^-1 at 298 K, surpassing the current top-ranking Cr-soc-MOF-1 (1.95 g g^-1). Isoreticular analogues, denoted as M-red-MOF-2 (M = Fe, Cr), were also synthesized using the anthracene-based linker H₄TEBDA. The present work opens new directions for designing ultraporous, hierarchical MOFs based on the red-a net.

A family of heterometallic Zn/Ca MOFs based on angular tetracarboxylic ligands with formulas [ZnCa(L)(S)(S')]_n (S, S' = H₂O or S = H₂O, S' = DMF) UCY-18(L) (H₄L = 4,4'-hexafluoroisopropilidene diphthalic acid (H₄HFPD), 3,3',4,4'-benzophenone tetracarboxylic acid (H₄BPTC), 4,4'-oxydiphthalic acid (H₄ODPA), 4,4'-azanediyl diphthalic acid (H₄ADPA)) is reported. The crystal structures of UCY-18(L) comprise 3-D networks based on helical one-dimensional chain SBUs [ZnCa(L^4-)] containing tetragonal channels along the crystallographic a-axis. Gas sorption studies on activated UCY-18(L) indicated appreciable BET surface areas ranging from 1338 to 2134 m² g^-1. Selected vapor sorption studies indicated the affinity of these materials toward representative C₆-aromatic and nonaromatic organic molecules. Thin films of UCY-18(HFPD), UCY-18(ODPA), and UCY-18(ADPA) embedded in poly(vinylidene fluoride) were fabricated and evaluated for their sensing capability for vapors of selected nitroaromatic compounds. The thin films exhibit high selectivity in detecting 2,4,6-trinitrophenol and 2,4,6-trinitrotoluene vapors among other nitroaromatic compounds and interferents at equal concentration. The crystal structures of UCY-18(HFPD) loaded with nitrobenzene and 2-nitrotoluene provided useful information about the interactions of the MOFs with these nitroaromatic molecules. Overall, this work highlights the potential of heterometallic Zn/Ca MOF chemistry to afford microporous MOFs containing highly accessible metal centers and displaying the capability to recognize vapors of selected analytes.

The rational design of ultraporous metal–organic frameworks (MOFs) with hierarchical pore systems is of great signifi-cance but remains highly challenging. MOFs based on the reo-e or red topologies offer this type of pore system originat-ed from face-shared cuboidal, cuboctahedral, and rhombicuboctahedral cages. For this reason, they have been hypothe-sized and computationally constructed over the past 20 years but have not yet been realized experimentally. We report herein the first examples of MOFs based on the awaited red-a net, denoted as M-red-MOF-1 (M: Fe3+, Cr3+). In particular, the use of the nearly square but with a rectangular connectivity 4-c linker 4,4',4'',4'''-([1,1':4',1''-terphenyl]-3,3'',5,5''-tetrayltetrakis(ethyne-2,1-diyl))tetrabenzoic acid, denoted as H4TCEPT, combined with FeCl3.6H2O under solvothermal reaction conditions, readily afforded Fe-red-MOF-1 as cubic-like single crystals. Extensive structural characterization using SCXRD for unit cell determination, PXRD, SEM, TEM imaging, detailed gas sorption isotherms and TGA, coupled with in-silico materials construction, confirmed that Fe-red-MOF-1 displays the red-a topology. Argon sorption iso-therm recorded at 87 K revealed the presence of three well defined S-type steps, in full agreement with the hierarchical pore network of the red-a net, with an ultrahigh pore volume of 3.56 cm3 g-1 and a BET surface area of 5080.6 m2 g-1. Pore size distribution analysis by fitting the Argon isotherm in the range 0.1-0.99 p/p0 revealed two peaks centered at 29.6 and 41.2 Å, associated with the cuboctahedral and rhombicuboctahedral cages in Fe-red-MOF-1. Notably, the isotherm below 0.1 p/p0 shows a concave shape rather than a convex one as expected for rigid frameworks. The formation of a flexible framework in Fe-red-MOF-1 is supported by SEM and TEM images, revealing that the faces of the cubic particles are curved inwards. These results are consistent with the observed reduced atomic periodicity in Fe-red-MOF-1, as revealed from high-resolution PXRD data. Because of its hierarchical ultrahigh porosity, the hydrogen storage properties of Fe-red-MOF-1 were investigated, revealing an exceptional gravimetric working capacity of 13.5 wt% and a high volumetric ca-pacity (39.5 g·L⁻¹) under temperature and pressure swing conditions (77 K/100 bar → 160 K/5 bar), placing this material among the top-performing MOFs. Finally, the isostructural Cr-red-MOF-1 was successfully synthesized by post-synthetic metal exchange reaction. The water sorption properties of this material were investigated by recording the corresponding isotherm at 298 K up to saturation, revealing an astonishing uptake of 2.81 g g-1, which is significantly larger than that of the current top-ranking MOF, Cr-soc-MOF-1 (1.95 g g-1). The present work opens new directions to apply reticular chem-istry for the construction of novel, ultraporous MOFs with hierarchical porosity, displaying the red-a net.

An important direction in MOFs is the development of materials with well‐defined and ordered heterogeneity toward novel functionalities and control of important properties at the atomic scale. A great approach is the designed synthesis of mixed‐metal MOFs (M'MOFs) made of different building units based on distinct metal cations. However, their in‐situ formation and co‐assembly into an extended crystalline framework present great challenges due to the different kinetic and thermodynamic parameters. We report the successful synthesis of two isostructural, bimetallic Zr‐Ni and Hf‐Ni M'MOFs following the hard and soft acid and base (HSAB) principle. Single‐crystal X‐ray diffraction analysis revealed the formation of a 3D structure that features an in‐situ formed [Ni(HPyC)₄Cl₂]⁴⁻ 4‐c nonplanar metallo‐ligand that bridges 8‐c Zr(Hf)₆‐clusters. The resulting (4, 8)‐c scu‐type framework shows polygonal 1D channels, with a largest pore diameter of approximately 9 Å, decorated by Cl⁻ anions. This polar pore environment was found fully accessible, and both materials were investigated for Xe/Kr and CO₂/CH₄ separation. The results are very promising, showing that the IAST selectivity calculated for a 20:80 Xe/Kr molar mixture is 8.2 and 7.1 at 298 K for the Zr_Ni‐scu‐MOF‐1 and Hf_Ni‐scu‐MOF‐1, respectively, which is comparable to some of the best‐performing materials.

Flexible Metal‐Organic Frameworks (FL‐MOFs) are emerging advanced materials with the ability to respond to various stimuli by adapting their structure and pore. In particular, FL‐MOFs based on rare‐earth (RE) elements offer a unique and sophisticated approach towards truly novel responsive materials and properties. This Concept article provides an overview of the main principles and factors that affect structural features in RE‐FL‐MOFs, identifying trends and exploring potential rational design strategies. Common challenges and possible future research directions are also discussed.

A desymmetrized 4-c linker directs the co-assembly of 6-c hexagonal and 10-c square bipyramidal rare-earth clusters, resulting in a unique six-nodal (3,3,3,3,6,10)-c net.

The water–gas shift (WGS) reaction is one of the most significant reactions in hydrogen technology since it can be used directly to produce hydrogen from the reaction of CO and water; it is also a side reaction taking place in the hydrocarbon reforming processes, determining their selectivity towards H₂ production. The development of highly active WGS catalysts, especially at temperatures below ~450 °C, where the reaction is thermodynamically favored but kinetically limited, remains a challenge. From a fundamental point of view, the reaction mechanism is still unclear. Since specific nanoshapes of CeO₂-based supports have recently been shown to play an important role in the performance of metal nanoparticles dispersed on their surface, in this study, a comparative study of the WGS is conducted on Pt nanoparticles dispersed (with low loading, 0.5 wt.% Pt) on CeO₂ and gadolinium-doped ceria (GDC) supports of different nano-morphologies, i.e., nanorods (NRs) and irregularly faceted particle (IRFP) CeO₂ and GDC, produced by employing hydrothermal and (co-)precipitation synthesis methods, respectively. The results showed that the support’s shape strongly affected its physicochemical properties and in turn the WGS performance of the dispersed Pt nanoparticles. Nanorod-shaped CeO_2,NRs and GDC_NRs supports presented a higher specific surface area, lower primary crystallite size and enhanced reducibility at lower temperatures compared to the corresponding irregular faceted CeO_2,IRFP and GDC_IRFP supports, leading to up to 5-fold higher WGS activity of the Pt particles supported on them. The Pt/GDC_NRs catalyst outperformed all other catalysts and exhibited excellent time-on-stream (TOS) stability. A variety of techniques, namely N₂ physical adsorption–desorption (the BET method), scanning and transmission electron microscopies (SEM and TEM), powder X-ray diffraction (PXRD) and hydrogen temperature programmed reduction (H₂-TPR), were used to identify the texture, structure, morphology and other physical properties of the materials, which together with the in situ diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS) and detailed kinetic studies helped to decipher their catalytic behavior. The enhanced metal–support interactions of Pt nanoparticles with the nanorod-shaped CeO_2,NRs and GDC_NRs supports due to the creation of more active sites at the metal–support interface, leading to significantly improved reducibility of these catalysts, were concluded to be the critical factor for their superior WGS activity. Both the redox and associative reaction mechanisms proposed for WGS in the literature were found to contribute to the reaction pathway.

The chemistry of metal-organic frameworks (MOFs) continues to expand rapidly, providing materials with diverse structures and properties. The reticular chemistry approach, where well-defined structural building blocks are combined together to form crystalline open framework solids, has greatly accelerated the discovery of new and important materials. However, its full potential toward the rational design of MOFs relies on the availability of highly connected building blocks because these greatly reduce the number of possible structures. Toward this, building blocks with connectivity greater than 12 are highly desirable but extremely rare. We report here the discovery of novel 18-connected, trigonal prismatic, ternary building blocks (tbb's) and their assembly into unique MOFs, denoted as Fe-tbb-MOF-x (x: 1, 2, 3), with hierarchical micro- and mesoporosity. The remarkable tbb is an 18-c supertrigonal prism, with three points of extension at each corner, consisting of triangular (3-c) and rectangular (4-c) carboxylate-based organic linkers and trigonal prismatic [Fe₃(μ₃-Ο)(-COO)₆]⁺ clusters. The tbb's are linked together by an 18-c cluster made of 4-c ligands and a crystallographically distinct Fe₃(μ₃-Ο) trimer, forming overall a 3-D (3,4,4,6,6)-c five nodal net. The hierarchical, highly porous nature of Fe-tbb-MOF-x (x: 1, 2, 3) was confirmed by recording detailed sorption isotherms of Ar, CH₄, and CO₂ at 87, 112, and 195 K, respectively, revealing an ultrahigh BET area (4263-4847 m² g^-1) and pore volume (1.95-2.29 cm³ g^-1). Because of the observed ultrahigh porosities, the H₂ and CH₄ storage properties of Fe-tbb-MOF-x were investigated, revealing well-balanced high gravimetric and volumetric deliverable capacities for cryoadsorptive H₂ storage (11.6 wt %/41.4 g L^-1, 77 K/100 bar-160 K/5 bar), as well as CH₄ storage at near ambient temperatures (367 mg g^-1/160 cm³ STP cm^-3, 5-100 bar at 298 K), placing these materials among the top performing MOFs. The present work opens new directions to apply reticular chemistry for the construction of novel MOFs with tunable porosities based on contracted or expanded tbb analogues.