Deciphering Reaction Products in Formamidine-Based Perovskites with Methylammonium Chloride Additive.

The fabrication of formamidinium lead iodide (FAPbI3) perovskite solar cells (PSCs) involves the addition of methylammonium chloride (MACl) to promote low-temperature α-phase formation and grain growth. However, as the added MACl deprotonates and volatilizes into methylamine (MA0) and HCl for removal, MA0 can chemically interact with formamidinium (FA+), forming methyl formamidinium (MFA+) as a byproduct. Despite its significance, the chemical interactions among FAPbI3 perovskites, MACl additives, and their byproducts remain poorly understood. Our findings reveal that the FA+ and MA0 reaction primarily yields a mixture of cis/trans-N-methyl formamidinium iodide (MFAI) isomers, with cis-MFAI prevailing as the dominant species. Moreover, MFAI subsequently reacts with PbI2 to yield fully formed cis-MFAPbI3 2H-phase perovskite. We elucidated the effects of MFAI on the crystal growth, phase stability, and band gap of formamidine-based perovskites through the growth of single crystals. This research offers valuable insights into the role of these byproducts in influencing the efficiency and long-term stability of future PSCs.

Creating Tunable Mesoporosity by Temperature-Driven Localized Crystallite Agglomeration.

A new synthetic approach for tunable mesoporous metal-organic frameworks (MeMs) is developed. In this approach, mesopores are created in the process of heat conversion of highly mosaic metal-organic framework (MOF) crystals with non-interpenetrated low-density nanocrystallites into MOF crystals with two-fold interpenetrated high-density nanocrystallites. The two-fold interpenetration reduces the volume of the nanocrystallites in the mosaic crystal, and the accompanying localized agglomeration of the nanocrystallites results in the formation of mesopores among the localized crystallite agglomerates. The pore size can be easily modulated from 7 to 90 nm by controlling the heat treatment conditions, that is, the aging temperature and aging time. Various proteins can be encapsulated in the MeM, and immobilized enzymes show catalyst activity comparable to that of the free native enzymes. Immobilized ß-galactosidase is recyclable and the enzyme activity of the immobilized catalase is maintained after exposure to high temperatures and various organic solvents.

The rise of metal-organic polyhedra.

Metal-organic polyhedra are a member of metal-organic materials, and are together with metal-organic frameworks utilized as emerging porous platforms for numerous applications in energy- and bio-related sciences. However, metal-organic polyhedra have been significantly underexplored, unlike their metal-organic framework counterparts. In this review, we will cover the topologies and the classification of metal-organic polyhedra and share several suggestions, which might be useful to synthetic chemists regarding the future directions in this rapid-growing field.

Superprotonic Conductivity of MOF-808 Achieved by Controlling the Binding Mode of Grafted Sulfamate.

A metal-organic framework (MOF) having superprotonic conductivity, MOF-808, is prepared by modulating the binding mode of the sulfamate (SA) moieties grafted onto the metal clusters. The activation of the SA-grafted MOF-808 at 150 °C changes the binding mode of the grafted SA from monodentate to bridging bidentate, thus converting the neutral amido (-S-NH2 ) moiety of the grafted SA to the more acidic cationic sulfiliminium (-S=NH2+ ) moiety. Further, the acidic sulfiliminium moiety of MOF-808-4SA-150 results in more efficient proton conduction than the amido moiety of MOF-808-4SA-60. At 60 °C and 95 % relative humidity, MOF-808-4SA-150 is found to have a proton conductivity of 7.89×10-2  S cm-1 , which is more than 30-times higher than that of MOF-808-4SA-60. Moreover, this superprotonic conductivity is well maintained over 1000 cycles of conductivity measurements and for similar cyclic measurements each day for seven days.

Amine-Tagged Fragmented Ligand Installation for Covalent Modification of MOF-74.

MOF-74 is one of the most explored metal-organic frameworks (MOFs), but its functionalization is limited to the dative post-synthetic modification (PSM) of the monodentate solvent site. Owing to the nature of the organic ligand and framework structure of MOF-74, the covalent PSM of MOF-74 is very demanding. Herein, we report, for the first time, the covalent PSM of amine-tagged defective Ni-MOF-74, which is prepared by de novo solvothermal synthesis by using aminosalicylic acid as a functionalized fragmented organic ligand. The covalent PSM of the amino group generates metal binding sites, and subsequent post-synthetic metalation with PdII ions affords the PdII -incorporated Ni-MOF-74 catalyst. This catalyst exhibits highly efficient, size-selective, and recyclable catalytic activity for the Suzuki-Miyaura cross-coupling reaction. This strategy is also useful for the covalent modification of amine-tagged defective Ni2 (DOBPDC), an expanded analogue of MOF-74.

Two-dimensional polyaniline (C3N) from carbonized organic single crystals in solid state.

The formation of 2D polyaniline (PANI) has attracted considerable interest due to its expected electronic and optoelectronic properties. Although PANI was discovered over 150 y ago, obtaining an atomically well-defined 2D PANI framework has been a longstanding challenge. Here, we describe the synthesis of 2D PANI via the direct pyrolysis of hexaaminobenzene trihydrochloride single crystals in solid state. The 2D PANI consists of three phenyl rings sharing six nitrogen atoms, and its structural unit has the empirical formula of C3N. The topological and electronic structures of the 2D PANI were revealed by scanning tunneling microscopy and scanning tunneling spectroscopy combined with a first-principle density functional theory calculation. The electronic properties of pristine 2D PANI films (undoped) showed ambipolar behaviors with a Dirac point of -37 V and an average conductivity of 0.72 S/cm. After doping with hydrochloric acid, the conductivity jumped to 1.41 × 10(3) S/cm, which is the highest value for doped PANI reported to date. Although the structure of 2D PANI is analogous to graphene, it contains uniformly distributed nitrogen atoms for multifunctionality; hence, we anticipate that 2D PANI has strong potential, from wet chemistry to device applications, beyond linear PANI and other 2D materials.

Hydrophobic Shielding of Outer Surface: Enhancing the Chemical Stability of Metal-Organic Polyhedra.

Metal-organic polyhedra (MOP) are a promising class of crystalline porous materials with multifarious potential applications. Although MOPs and metal-organic frameworks (MOFs) have similar potential in terms of their intrinsic porosities and physicochemical properties, the exploitation of carboxylate MOPs is still rudimentary because of the lack of systematic development addressing their chemical stability. Herein we describe the fabrication of chemically robust carboxylate MOPs via outer-surface functionalization as an a priori methodology, to stabilize those MOPs system where metal-ligand bond is not so strong. Fine-tuning of hydrophobic shielding is key to attaining chemical inertness with retention of the framework integrity over a wide range of pH values, in strong acidic conditions, and in oxidizing and reducing media. These results are further corroborated by molecular modelling studies. Owing to the unprecedented transition from instability to a chemically ultra-stable regime using a rapid ambient-temperature gram-scale synthesis (within seconds), a prototype strategy towards chemically stable MOPs is reported.

Zirconium-Formate Macrocycles and Supercage: Molecular Packing versus MOF-like Network for Water Vapor Sorption.

In systematic efforts toward a new type of molecule-based porous materials, facile and efficient synthetic methods have been established to obtain macrocyclic [Zr6]6 and supercage-like {[Zr6]6}8, where [Zr6] represents [Zr6O4(OH)4(CO2) n] building unit commonly found in Zr-based metal-organic frameworks. The reactions involve in situ hydrolysis of DMF solvent to produce formate linkers and thus do not require any organic ligand. A minor variation in the composition of two cyclic hexamers thus obtained results in dramatic differences in crystal packing which in turn lead to distinctive and selective sorption behavior for water vapor. It is shown that the high heat of water adsorption and unrestricted uptake under high humidity are consequences of the highly polar surface and flexible crystal packing. The reversibility of water adsorption is demonstrated by cyclic measurements of uptake and regeneration under dynamic flow conditions.

Coordination-Driven Self-Assembly of Heterotrimetallic Barrel and Bimetallic Cages Using a Cobalt Sandwich-Based Tetratopic Donor.

Three-dimensional molecular architectures self-assembled with tripodal and tetratopic donors are valuable because of their encapsulation properties. Here, we present Co(I)-Fe(II)-Pd(II) heterotrimetallic trifacial barrel 1, which was self-assembled using a newly synthesized tetratopic donor [CpCo(CbR4)] [L; Cp = cyclopentadienyl, Cb = cyclobudiene, and R = 4-(4-pyridylphenyl)] and a 90° acceptor [ cis-(dppf)Pd(OTf)2] (A1; dppf = (diphenylphosphino)ferrocene and OTf = CF3SO3-). The heterotrimetallic barrel 1 exhibited selective 1:1 interaction with a N, N'-dimethyl-1,4,5,8-naphthalenetetracarboxylic diimide guest, as revealed by 1H NMR analysis. The self-assembly of donor L with two other Ru(II)-based 180° acceptors [( p-cymene)2Ru2(OO∩OO)(OTf)2] [OO∩OO = 6,11-dioxido-5,12-naphthacenedione (A2) and oxalate (A3)] resulted in tetragonal-prismatic cages. Self-assembly using the longer acceptor A2 provided rare isomers of a tetragonal-prismatic cage by varying the orientation of the cyclopentadienyl moiety out-out (2a) or out-in (2b) of the cavity, whereas self-assembly using the shorter acceptor A3 selectively resulted in the tetragonal-prismatic cage 3. The three-dimensional molecular architectures 1-3 were characterized by combined spectroscopic and elemental analyses. The structures of molecular barrel 1 and prismatic cage 3 were elucidated by single-crystal X-ray analysis.

Unusually Stable Triazine-based Organic Superstructures.

Solid-state reactions have been rapidly gaining popularity in organic chemistry owing to their simplicity, efficiency, and selectivity compared to liquid-phase reactions. Herein, we describe the formation of superstructures through the solid-state reaction of an organic single-crystal. The superstructure of 5,5',5''-(1,3,5-triazine-2,4,6-triyl)triisophthalonitrile (TIPN) can be formed by cyclotrimerization of 1,3,5-tricyanobenzene (TCB) single crystals. The TIPN superstructure was confirmed by single crystal X-ray diffraction and visualized by transmission electron microscopy. The superstructure has hexagonally packed 1-dimensional (1D) channels along the crystal axis. Furthermore, the superstructure arises from interdigitated nitrile interactions in the crystal lattice, and thus has electron-beam tolerance and very high thermal stability.

A supermolecular building approach for the design and construction of metal-organic frameworks.

In this review, we describe two recently implemented conceptual approaches facilitating the design and deliberate construction of metal­organic frameworks (MOFs), namely supermolecular building block (SBB) and supermolecular building layer (SBL) approaches. Our main objective is to offer an appropriate means to assist/aid chemists and material designers alike to rationally construct desired functional MOF materials, made-to-order MOFs. We introduce the concept of net-coded building units (net-cBUs), where precise embedded geometrical information codes uniquely and matchlessly a selected net, as a compelling route for the rational design of MOFs. This concept is based on employing pre-selected 0-periodic metal­organic polyhedra or 2-periodic metal­organic layers, SBBs or SBLs respectively, as a pathway to access the requisite net-cBUs. In this review, inspired by our success with the original rht-MOF, we extrapolated our strategy to other known MOFs via their deconstruction into more elaborate building units (namely polyhedra or layers) to (i) elucidate the unique relationship between edge-transitive polyhedra or layers and minimal edge-transitive 3-periodic nets, and (ii) illustrate the potential of the SBB and SBL approaches as a rational pathway for the design and construction of 3-periodic MOFs. Using this design strategy, we have also identified several new hypothetical MOFs which are synthetically targetable.

Anticancer potency studies of coordination driven self-assembled arene­Ru-based metalla-bowls.

New tetranuclear cationic metalla-bowls 5­7 with the general formula [Ru4(p-cymene)4(N∩N)2(OO∩OO)2]4+ (N∩N=2,6-bis(N-(4-pyridyl carbamoyl)pyridine, OO∩OO=2,5-dihydroxy-1,4-benzoquinonato (5), OO∩OO=5,8-dioxydo-1,4-naphthaquinonato (6), OO∩OO=hoxonato (7)) were prepared by the reaction of the respective dinuclear ruthenium complexes 2­4 with a bispyridine amide donor ligand 1 in methanol in the presence of AgO3SCF3.These new molecular metalla-bowls were fully characterized by analytical techniques including elemental analysis as well as 1H and 13C NMR and HR-ESI-MS spectroscopy. The structure of metalla-bowl 6 was determined from X-ray crystal diffraction data. A UV/visible study was also carried out for the entire suite of new complexes. As with recent studies of similar arene­Ru complexes, the inhibition of cell growth by metalla-bowls was established against SK-hep-1 (liver cancer), AGS (gastric cancer), and HCT-15 (colorectal cancer) human cancer cell lines. Inhibition of cell growth by 6 was found to be considerably stronger against all cancer cell lines than the anticancer drugs, doxorubicin and cisplatin. In particular, in colorectal cancer cells, expression of the cancer suppressor genes APC and p53 was increased following exposure to 6.

A multifunctional protein pre-coated metal-organic framework for targeted delivery with deep tissue penetration.

Targeted drug delivery using metal-organic frameworks (MOFs) has shown significant progress. However, the tumor microenvironment (TME) impedes efficient MOF particle transfer into tumor cells. To tackle this issue, we pre-coated nano-sized MOF-808 particles with multifunctional proteins: glutathione S-transferase (GST)-affibody (Afb) and collagenase, aiming to navigate the TME more effectively. The surface of MOF-808 particles is coated with GST-Afb-a fusion protein of GST and human epidermal growth factor receptor 2 (HER2) Afb or epidermal growth factor receptor (EGFR) Afb which has target affinity. We also added collagenase enzymes capable of breaking down collagen in the extracellular matrix (ECM) through supramolecular conjugation, all without chemical modification. By stabilizing these proteins on the surface, GST-Afb mitigate biomolecule absorption, facilitating specific tumor cell targeting. Simultaneously, collagenase degrades the ECM in the TME, enabling deep tissue penetration of MOF particles. Our resulting system, termed collagenase-GST-Afb-MOF-808 (Col-Afb-M808), minimizes undesired interactions between MOF particles and external biological proteins. It not only induces cell death through Afb-mediated cell-specific targeting, but also showcases advanced cellular internalization in 3D multicellular spheroid cancer models, with effective deep tissue penetration. The therapeutic efficacy of Col-Afb-M808 was further assessed via in vivo imaging and evaluation of tumor inhibition following injection of IR-780 loaded Col-Afb-M808 in 4T1tumor-bearing nude mice. This study offers key insights into the regulation of the multifunctional protein-adhesive surface of MOF particles, paving the way for the designing even more effective targeted drug delivery systems with nano-sized MOF particles.

Unveiling the Power of Cloaking Metal-Organic Framework Platforms via Supramolecular Antibody Conjugation.

Targeted drug delivery systems based on metal-organic frameworks (MOFs) have progressed tremendously since inception and are now widely applicable in diverse scientific fields. However, translating MOF agents directly to targeted drug delivery systems remains a challenge due to the biomolecular corona phenomenon. Here, we observed that supramolecular conjugation of antibodies to the surface of MOF particles (MOF-808) via electrostatic interactions and coordination bonding can reduce protein adhesion in biological environments and show stealth shields. Once antibodies are stably conjugated to particles, they were neither easily exchanged with nor covered by biomolecule proteins, which is indicative of the stealth effect. Moreover, upon conjugation of the MOF particle with specific targeted antibodies, namely, anti-CD44, human epidermal growth factor receptor 2 (HER2), and epidermal growth factor receptor (EGFR), the resulting hybrid exhibits an augmented targeting efficacy toward cancer cells overexpressing these receptors, such as HeLa, SK-BR-3, and 4T1, as evidenced by flow cytometry. The therapeutic effectiveness of the antibody-conjugated MOF (anti-M808) was further evaluated through in vivo imaging and the assessment of tumor inhibition effects using IR-780-loaded EGFR-M808 in a 4T1 tumor xenograft model employing nude mice. This study therefore provides insight into the use of supramolecular antibody conjugation as a promising method for developing MOF-based drug delivery systems.

Hybrid bimetallic metal-organic frameworks: modulation of the framework stability and ultralarge CO2 uptake capacity.

A series of isostructural hybrid bimetallic metal-organic frameworks (MOFs), Ni(x)M(1-x)-ITHDs [M = Zn(II), Co(II)], have been prepared via a conventional solvothermal reaction in the presence of varying mole ratios of Ni(II)/Zn(II) or Ni(II)/Co(II) mixed metal ions. While a critical amount of the doped Ni(II) ion (more than ≈0.2 mol fraction) is needed to have any enhancement of the framework stability of the hybrid bimetallic NixZn1-x-ITHDs, even a very small amount of the doped Ni(II) ion (≈0.1 mol fraction) produced a full enhancement of the framework stability of the hybrid bimetallic Ni(x)Co(1-x)-ITHDs. The highly porous and rigid Ni(x)Co(1-x)-ITHDs activated via a conventional vacuum drying process shows a Brunauer-Emmett-Teller specific surface area of 5370 m(2) g(-1), which is comparable to that of pure Ni-ITHD. The CO2 uptake capacities of Ni-ITHD and Ni(0.11)Co(0.89)-ITHD (2.79 and 2.71 g g(-1), respectively) at 1 bar and 195 K are larger than those of any other reported MOFs under similar conditions and the excess CO2 uptake capacity at 40 bar and 295 K (≈1.50 g g(-1)) is comparable to those of other MOFs, which are activated via the supercritical carbon dioxide drying process, with similar pore volumes.

Crystal-to-crystal transformations of a series of isostructural metal-organic frameworks with different sizes of ligated solvent molecules.

Isostructural 3D metal-organic frameworks (MOFs) [Zn2(BTC)(NO3)S3] [where BTC = 1,3,5-benzenetricarboxylate; S = EtOH (1), DMF (2), DMA (3), or DEF (4)] of a 3-connected srs net topology have been prepared in the presence of serine as a template. The MOFs show different framework stabilities depending on the sizes of the ligated solvent molecules and undergo a crystal-to-crystal transformation at ambient conditions into a 1D chain structure either directly or via different types of intermediates depending on the ligated solvent molecules and the sample handling conditions. A single crystal of the MOF with the ligated DMF molecules, [Zn2(BTC)(NO3)(DMF)3] (2), is stable in Mg(II)- and Co(II)-DMF solutions; however, it transforms into a single particle-like microcrystalline aggregate of Cu-HKUST-1 in a Cu(II)-DMF solution.

Synthesis and characterization of self-assembled nanoscopic metallarectangles capable of binding fullerenes with size-selective responses.

Two new metallarectangles, 4 and 5, were obtained from the self-assembly of areneruthenium-based molecular clips 2 and 3 with a new dipyridyl donor ligand 1 containing a diamide core and ethynyl spacers. The metallarectangles were characterized by multinuclear NMR, electrospray ionization mass spectrometry, and UV-vis spectroscopy, and the molecular structure of 4 was unambiguously determined by single-crystal X-ray diffraction analysis. Because of the presence of an extended π-electron aromatic surface, the tetracene-containing molecular rectangle 5 was capable of binding C60 and C70 fullerenes as quantified by UV-vis, emission, and (1)H NMR experiments, providing an example of a supramolecular host capable of recognizing large guest molecules.

Solvent-induced structural dynamics in noninterpenetrating porous coordination polymeric networks.

Three novel soft porous coordination polymer (PCP) or metal-organic framework (MOF) compounds have been synthesized with a new rigid ligand N-(4-pyridyl)-1,4,5,8-naphathalenetetracarboxymonoimide (PNMI) by partial hydrolysis of N,N'-di-(4-pyridyl)-1,4,5,8-naphthalenete-tracarboxydiimide (DPNI) during solvothermal reactions with Zn(II), Cd(II), and Mn(II) salts, and they are [Zn(PNMI)]·2DMA (1·2DMA, 1a), [Cd(PNMI)]·0.5DMA·5H2O (2·0.5DMA·5H2O), and [Mn(PNMI)]·0.75DMF (3·0.75DMF). The structure of 1 is based on paddle-wheel secondary building unit (SBU) with a 3,6-connected rtl net topology, whereas 2 and 3 are isotypical but the M(O2C-C)2 fragments aggregate in one-dimension and the overall connectivity is the same rtl net topology. All these three MOFs have one-dimensional rhombic channels filled with guest molecules. The guest molecules in 1a can be exchanged with EtOH in a single-crystal to single-crystal (SCSC) manner to 1·1.25EtOH·0.375H2O (1b). Further, the guest molecules in 1b can be replaced with ethylene glycol, triethylene glycol and allyl alcohol without destroying its single crystal nature. These guest exchanges are accompanied by reduction in volume of the unit cell up to 16%, as well as the void volume up to 33.1%. Similarly, triethylene glycol (TEGly) selectively exchanges EtOH in a mixture of the above solvents, which might be the result of correct fit of the hydrogen-bonded TEGly dimer in the channel of 1. While activated 1 and 3 exhibit no uptake of N2 and H2 at 1 bar and 77 K and very low uptake of CO2 gas at 1 bar and 196 K, activated 2 shows selective CO2 uptake, 278 cm(2)·g(-1), over N2 and H2 at 1 bar and 196 K, which corresponds to 5.87 molecules of CO2 per formula unit of 2.

Metal-Organic Framework-Supported Catalase Delivery for Enhanced Photodynamic Therapy via Hypoxia Mitigation.

Tumor hypoxia poses a significant challenge in photodynamic therapy (PDT), which uses molecular oxygen to produce reactive oxygen species upon light excitation of a photosensitizer. For hypoxia mitigation, an enzyme catalase (CAT) can be beneficially used to convert intracellular hydrogen peroxide to molecular oxygen, but its utility is significantly limited due to the intrinsic membrane impermeability. Herein, we present direct integration of CAT into the outer surface of unmodified metal-organic framework (MOF) nanoparticles (NPs) via supramolecular interactions for effective cellular entry of CAT and consequent enhancement of PDT. The results demonstrated that CAT-loaded MOF NPs could successfully enter hypoxic cancer cells, after which the intracellularly delivered CAT molecules became dissociated from the MOF surface to efficiently initiate the oxygen generation and PDT process along with a co-delivered photosensitizer IR780. This achievement suggests that our protein-MOF integration strategy holds great potential in biomedical studies to overcome tumor hypoxia as well as to efficiently deliver biomolecular cargos.

Symmetry-Mismatched SBU Transformation in MOFs: Postsynthetic Metal Exchange from Zn to Fe and Its Effects on Gas Adsorption and Dye Selectivity.

This research explores the alteration of metal-organic frameworks (MOFs) using a method called postsynthetic metal exchange. We focus on the shift from a Zn-based MOF containing a [Zn4O(COO)6] secondary building unit (SBU) of octahedral site symmetry (ANT-1(Zn)) to a Fe-based one with a [Fe3IIIO(COO)6]+ SBU of trigonal prismatic site symmetry (ANT-1(Fe)). The symmetry-mismatched SBU transformation cleverly maintains the MOF's overall structure by adjusting the conformation of the flexible 1,3,5-benzenetribenzoate linker to alleviate the framework strain. The process triggers a decrease in the framework volume and pore size alongside a change in the framework's charge. These alterations influence the MOF's ability to adsorb gas and dye. During the transformation, core-shell MOFs (ANT-1(Zn@Fe)) are formed as intermediate products, demonstrating unique gas sorption traits and adjusted dye adsorption preferences due to the structural modifications at the core-shell interface. Heteronuclear clusters, located at the framework interfaces, enhance the heat of CO2 adsorption. Furthermore, they also influence the selectivity of the dye size. This research provides valuable insights into fabricating novel MOFs with unique properties by modifying the SBU of a MOF with flexible organic linkers from one site symmetry to another.