Rare Earth alb-MOFs: From Synthesis to Their Deployment for Amine-Sensing Application in Aqueous Media.

The pursuit of developing sensors, characterized by their fluorescence-intensity enhancement or "turn-on" behavior, for accurately detecting noxious small molecules, such as amines, at minimal levels remains a significant challenge. Metal-organic frameworks (MOFs) have emerged as promising candidates as sensors as a result of their diverse structural features and tunable properties. This study introduces the rational synthesis of a new highly coordinated (6,12)-connected rare earth (RE) alb-MOF-3, by combining the nonanuclear 12-connected hexagonal prismatic building units, [RE9(µ3-O)2(µ3-X)12(OH)2(H2O)7(O2C-)12], with the 6-connected rigid trigonal prismatic extended triptycene ligand. The resulting Y-alb-MOF-3 material is distinguished by its high microporosity and Brunauer-Emmett-Teller surface area of approximately 1282 m2/g, which offers notable hydrolytic stability. Remarkably, it demonstrates selective detection capabilities for primary aliphatic amines in aqueous media, as evidenced by fluorescence turn-on behavior and photoluminescence (PL) titration measurements. This work emphasizes the potential of MOFs as sensors in advancing their selectivity and sensitivity toward various analytes.

Tunable Low-Relative Humidity and High-Capacity Water Adsorption in a Bibenzotriazole Metal-Organic Framework.

Materials capable of selectively adsorbing or releasing water can enable valuable applications ranging from efficient humidity and temperature control to the direct atmospheric capture of potable water. Despite recent progress in employing metal-organic frameworks (MOFs) as privileged water sorbents, developing a readily accessible, water-stable MOF platform that can be systematically modified for high water uptake at low relative humidity remains a significant challenge. We herein report the development of a tunable MOF that efficiently captures atmospheric water (up to 0.78 g water/g MOF) across a range of uptake humidity (27-45%) employing a readily accessible Zn bibenzotriazolate MOF, CFA-1 ([Zn5(OAc)4(bibta)3], H2bibta = 1H,1H'-5,5'-bibenzo[d][1,2,3]triazole), as a base for subsequent diversification. Controlling the metal identity (zinc, nickel) and coordinating nonstructural anion (acetate, chloride) via postsynthetic exchange modulates the relative humidity of uptake, facilitating the use of a single MOF scaffold for a diverse range of potential water sorption applications. We further present a fundamental theory dictating how continuous variation of the pore environment affects the relative humidity of uptake. Exchange of substituents preserves capacity for water sorption, increases hydrolytic stability (with 5.7% loss in working capacity over 450 water adsorption-desorption cycles for the nickel-chloride-rich framework), and enables continuous modulation for the relative humidity of pore condensation. This combination of stability and tunability within a synthetically accessible framework renders Ni-incorporated M5X4bibta3 promising materials for practical water sorption applications.

Reticular Chemistry for the Construction of Highly Porous Aluminum-Based nia-Metal-Organic Frameworks.

Edge-transitive nets are regarded as appropriate blueprints for the practice of reticular chemistry, and in particular, for the rational design and synthesis of functional metal-organic frameworks (MOFs). Among edge-transitive nets, type I edge-transitive nets have unique coordination figures, offering only one edge-transitive target for their associated expressed net-cBUs. Here, we report the reticulation of the binodal edge-transitive (6, 6)-c nia net in MOF chemistry, namely, the deliberate assembly of trinuclear aluminum clusters and 6-connected hexacarboxylate ligands into highly porous nia-MOFs. Further studies reveal that Al-nia-MOF-1 shows promising attributes as a storage media for oxygen (O2) at high-pressure adsorption studies.

Enriching the Reticular Chemistry Repertoire with Minimal Edge-Transitive Related Nets: Access to Highly Coordinated Metal-Organic Frameworks Based on Double Six-Membered Rings as Net-Coded Building Units.

Minimal edge-transitive nets are regarded as suitable blueprints for the successful practice of reticular chemistry, and par excellence ideal for the deliberate design and rational construction of highly coordinated metal-organic frameworks (MOFs). We report the systematic generation of the highly connected minimal edge-transitive related nets (transitivity [32]) from parent edge-transitive nets (transitivity [21] or [11]), and their use as a guide for the deliberate design and directional assembly of highly coordinated MOFs from their associated net-coded building units (net-cBUs), 12-connected (12-c) double six-membered ring (d6R) building units. Notably, the generated related nets enclose the distinctive highly coordinated d6R (12-c) due to the subsequent coordination number increase in one node of the resultant new related net; that is, the (3,4,12)-c kce net is the (4,6)-c soc-related net, and the (3,6,12)-c kex and urx nets are the (6,6)-c nia-related nets. Intuitively, the combination of 12-connected hexagonal prismatic rare-earth (RE) nonanuclear [RE9(µ3-O)2(µ3-OH)12(O2C-)12] carboxylate-based clusters with purposely chosen organic or organic-inorganic hybrid building units led to the formation of the targeted highly coordinated MOFs based on selected minimal edge-transitive related nets. Interestingly, the kex-MOFs can alternatively be regarded as a zeolite-like MOF (ZMOF) based on the zeolite underlying topology afx, by considering the dodecacarboxylate ligand as a d6R building unit, delineating a new avenue toward the construction of ZMOFs through the composite building units as net-cBUs. This represents a significant step toward the effective discovery and design of novel minimal edge-transitive and highly coordinated materials using the d6Rs as net-cBUs.

Reticular Chemistry at Its Best: Directed Assembly of Hexagonal Building Units into the Awaited Metal-Organic Framework with the Intricate Polybenzene Topology, pbz-MOF.

The ability to direct the assembly of hexagonal building units offers great prospective to construct the awaited and looked-for hypothetical polybenzene (pbz) or "cubic graphite" structure, described 70 years ago. Here, we demonstrate the successful use of reticular chemistry as an appropriate strategy for the design and deliberate construction of a zirconium-based metal-organic framework (MOF) with the intricate pbz underlying net topology. The judicious selection of the perquisite hexagonal building units, six connected organic and inorganic building blocks, allowed the formation of the pbz-MOF-1, the first example of a Zr(IV)-based MOF with pbz topology. Prominently, pbz-MOF-1 is highly porous, with associated pore size and pore volume of 13 Å and 0.99 cm3 g-1, respectively, and offers high gravimetric and volumetric methane storage capacities (0.23 g g-1 and 210.4 cm3 (STP) cm-3 at 80 bar). Notably, the pbz-MOF-1 pore system permits the attainment of one of the highest CH4 adsorbed phase density enhancements at high pressures (0.15 and 0.21 g cm-3 at 35 and 65 bar, respectively) as compared to benchmark microporous MOFs.

MOF Crystal Chemistry Paving the Way to Gas Storage Needs: Aluminum-Based soc-MOF for CH4, O2, and CO2 Storage.

The molecular building block approach was employed effectively to construct a series of novel isoreticular, highly porous and stable, aluminum-based metal-organic frameworks with soc topology. From this platform, three compounds were experimentally isolated and fully characterized: namely, the parent Al-soc-MOF-1 and its naphthalene and anthracene analogues. Al-soc-MOF-1 exhibits outstanding gravimetric methane uptake (total and working capacity). It is shown experimentally, for the first time, that the Al-soc-MOF platform can address the challenging Department of Energy dual target of 0.5 g/g (gravimetric) and 264 cm(3) (STP)/cm(3) (volumetric) methane storage. Furthermore, Al-soc-MOF exhibited the highest total gravimetric and volumetric uptake for carbon dioxide and the utmost total and deliverable uptake for oxygen at relatively high pressures among all microporous MOFs. In order to correlate the MOF pore structure and functionality to the gas storage properties, to better understand the structure-property relationship, we performed a molecular simulation study and evaluated the methane storage performance of the Al-soc-MOF platform using diverse organic linkers. It was found that shortening the parent Al-soc-MOF-1 linker resulted in a noticeable enhancement in the working volumetric capacity at specific temperatures and pressures with amply conserved gravimetric uptake/working capacity. In contrast, further expansion of the organic linker (branches and/or core) led to isostructural Al-soc-MOFs with enhanced gravimetric uptake but noticeably lower volumetric capacity. The collective experimental and simulation studies indicated that the parent Al-soc-MOF-1 exhibits the best compromise between the volumetric and gravimetric total and working uptakes under a wide range of pressure and temperature conditions.

Quest for highly connected metal-organic framework platforms: rare-earth polynuclear clusters versatility meets net topology needs.

Gaining control over the assembly of highly porous rare-earth (RE) based metal-organic frameworks (MOFs) remains challenging. Here we report the latest discoveries on our continuous quest for highly connected nets. The topological exploration based on the noncompatibility of a 12-connected RE polynuclear carboxylate-based cluster, points of extension matching the 12 vertices of the cuboctahedron (cuo), with 3-connected organic ligands led to the discovery of two fascinating and highly connected minimal edge-transitive nets, pek and aea. The reduced symmetry of the employed triangular tricarboxylate ligand, as compared to the prototype highly symmetrical 1,3,5-benzene(tris)benzoic acid guided the concurrent occurrence of nonanuclear [RE9(µ3-OH)12(µ3-O)2(O2C-)12] and hexanuclear [RE6(OH)8(O2C-)8] carboxylate-based clusters as 12-connected and 8-connected molecular building blocks in the structure of a 3-periodic pek-MOF based on a novel (3,8,12)-c trinodal net. The use of a tricarboxylate ligand with modified angles between carboxylate moieties led to the formation of a second MOF containing solely nonanuclear clusters and exhibiting once more a novel and a highly connected (3,12,12)-c trinodal net with aea topology. Notably, it is the first time that RE-MOFs with double six-membered ring (d6R) secondary building units are isolated, representing therefore a critical step forward toward the design of novel and highly coordinated materials using the supermolecular building layer approach while considering the d6Rs as building pillars. Lastly, the potential of these new MOFs for gas separation/storage was investigated by performing gas adsorption studies of various probe gas molecules over a wide range of pressures. Noticeably, pek-MOF-1 showed excellent volumetric CO2 and CH4 uptakes at high pressures.