Search

Metal–organic frameworks (MOFs) have shown promise in both capturing CO2under flue gas conditions and converting it into valuable chemicals. However, the development of a single MOF capable of capturing and selectively converting CO2has remained elusive due to a lack of a harmonious combination of selectivity, water stability, and reactivity. For example, Cu(I)-based MOFs are particularly effective for CO2conversion, but they do not typically exhibit selective CO2adsorption and often suffer from instability in the presence of air and moisture. Developing a Cu(I) MOF that is stable under flue gas conditions while also capturing CO2from this mixture would likely afford a material capable of selectively capturing and converting CO2in an integrated pathway, which would represent a significant advancement in this field. In this study, we introduce NU-2100, an ultramicroporous Cu(I) MOF, which exhibits both selectivity for CO2adsorption and great stability even in the presence of moisture and air. Comprehensive evaluations involving exposure to air, oxygen, water, and varying temperatures reveal that NU-2100demonstrates superior stability compared to other known Cu(I) MOFs. Utilizing adsorption isotherms and thermogravimetric analysis coupled with gas chromatography–mass spectrometry (TGA-GCMS), we establish the high selectivity of NU-2100for CO2over common flue gas components, including water, nitrogen, and oxygen. Additionally, under mild reaction conditions (50 °C and H2:CO2= 3:1), NU-2100exhibits CO2capture and catalytic conversion to formic acid with 100% selectivity. This study marks an important step toward the design of next-generation MOFs capable of integrated carbon capture and utilization (iCCU) under industrial conditions.

One of the primary methods for band gap tuning in metal halide perovskites has been halide (I/Br) mixing. Despite widespread usage of this type of chemical substitution in perovskite photovoltaics, there is still little understanding of the structural impacts of halide alloying, with the assumption being the formation of ideal solid solutions. The FASnI3–xBrx(x= 0–3) family of compounds provides the first example where the assumption breaks down, as the composition space is broken into two unique regimes (x= 0–2.9; x= 2.9–3) based on their average structure with the former having a 3D and the latter having an extended 3D (pseudo 0D) structure. Pair distribution function (PDF) analyses further suggest a dynamic 5s2lone pair expression resulting in increasing levels of off-centering of the central Sn as the Br concentration is increased. These antiferroelectric distortions indicate that even the x= 0–2.9 phase space behaves as a nonideal solid-solution on a more local scale. Solid-state NMR confirms the difference in local structure yielding greater insight into the chemical nature and local distributions of the FA+cation. In contrast to the FAPbI3–xBrxseries, a drastic photoluminescence (PL) quenching is observed with x≥ 1.9 compounds having no observable PL. Our detailed studies attribute this quenching to structural transitions induced by the distortions of the [SnBr6] octahedra in response to stereochemically expressed lone pairs of electrons. This is confirmed through density functional theory, having a direct impact on the electronic structure.

Industrialization over the past two centuries has resulted in a continuous rise in global CO2emissions. These emissions are changing ecosystems and livelihoods. Therefore, methods are needed to capture these emissions from point sources and possibly from our atmosphere. Though the amount of CO2is rising, it is challenging to capture directly from air because its concentration in air is extremely low, 0.04%. In this study, amines installed inside metal–organic frameworks (MOFs) are investigated for the adsorption of CO2, including at low concentrations. The amines used are polyamidoamine dendrimers that contain many primary amines. Chemically reversible adsorption of CO2via carbamate formation was observed, as was enhanced uptake of carbon dioxide, likely via dendrimer-amide-based physisorption. Limiting factors in this initial study are comparatively low dendrimer loadings and slow kinetics for carbon dioxide uptake and release, even at 80 °C.

We studied and established the dual nature of non-isocyanate polythiourethane (NIPTU) dynamic chemistry and capitalized on our understanding to achieve multidimensional chemical recycling of a cross-linked NIPTU, also known as poly(mercapto-thiourethane). This NIPTU chemical recycling includes the first demonstration of recovery of valuable small molecules in addition to reprocessability with full cross-link density recovery. In particular, we performed the first investigation of NIPTU dynamic chemistry using small-molecule analogues. We identified two types of dynamic chemistry: reversible cyclic thiocarbonate aminolysis, where the non-isocyanate thiourethane (NITU) groups in NIPTU reversibly dissociate into cyclic thiocarbonates and amines, and trans(thio)carbamoylation, where the thionourethane linkages within the NITU groups undergo exchange reactions with alcohol. We synthesized a renewable glycerol-based NIPTU (GNIPTU) with a high biowaste-derivable content. Capitalizing on trans(thio)carbamoylation, we recovered pure di(thiocarbamate) small molecules with a 94 mol % yield, one of the highest yields among reported studies of chemical recycling of polymers. The GNIPTU network exhibited full property recovery after reprocessing, providing another effective method of chemical recycling. With robust properties, high biowaste-derivable content, the capability to undergo multidimensional chemical recycling with excellent small-molecule recovery, and full reprocessability, the GNIPTU network exemplifies how low-cost, renewable, non-isocyanate polyurethane-like materials can be developed with both high-performance characteristics and the potential to contribute meaningfully to polymer circularity.

The storage of hydrogen is key to its applications. Developing adsorbent materials with high volumetric and gravimetric storage capacities, both of which are essential for the efficient use of hydrogen as a fuel, is challenging. Here we report a controlled catenation strategy in hydrogen-bonded organic frameworks (RP-H100 and RP-H101) that depends on multiple hydrogen bonds to guide catenation in a point-contact manner, resulting in high volumetric and gravimetric surface areas, robustness and ideal pore diameters (~1.2–1.9 nm) for hydrogen storage. This approach involves assembling nine imidazole-annulated triptycene hexaacids into a secondary hexagonal superstructure containing three open channels through which seven of the hexagons interpenetrate to form a seven-fold catenated superstructure. RP-H101 exhibits high deliverable volumetric (53.7 g l−1) and gravimetric (9.3 wt%) capacities for hydrogen under a combined temperature and pressure swing (77 K/100 bar → 160 K/5 bar). This work illustrates the virtues of supramolecular crystals as promising candidates for hydrogen storage.

RbEuFe4As4exhibits a rare combination of high-temperature superconductivity and noncollinear magnetism, originating from the FeAs and Eu layers, respectively. In order to fine-tune its superconducting and magnetic properties, we studied P-doped RbEuFe4As4–xPx. To determine the value of xfor which RbEuFe4As4–xPxexists, members of the series have been synthesized in the form of relatively large-sized single crystals by a high-temperature flux growth technique using RbAs flux as well as polycrystalline powder by direct combination reactions between RbFe2As2and EuFe2As2–xPx. The flux crystal growth reactions indicate that RbEuFe4As4–xPxforms with the values of x≤ 0.12, which is corroborated by the Rietveld refinement analysis on the products obtained from direct combination reactions. The solubility limit exists primarily due to the preferential site As(2) occupation by P in the RbEuFe4As4crystal structure. As xincreases in RbEuFe4As4–xPx, magnetization measurements reveal that the superconducting critical transition temperature (Tc) decreases, while the magnetic ordering temperature (TN) remains almost unchanged in comparison to undoped RbEuFe4As4.

Two-dimensional covalent organic frameworks (2D COFs) form as layered 2D polymers whose sheets stack through high-surface-area, noncovalent interactions that can give rise to different interlayer arrangements. Manipulating the stacking of 2D COFs is crucial since it dictates the effective size and shape of the pores as well as the specific interactions between functional aromatic systems in adjacent layers, both of which will strongly influence the emergent properties of 2D COFs. However, principles for tuning layer stacking are not yet well understood, and many 2D COFs are disordered in the stacking direction. Here, we investigate effects of pendant chain length through a series of 2D imine-linked COFs functionalized with n-alkyloxy chains varying in length from one carbon (C1COF) to 11 carbons (C11COF). This series reveals previously unrecognized and unanticipated trends in both the stacking geometry and crystallinity. C1COFadopts an averaged eclipsed geometry with no apparent offset between layers. In contrast, all subsequent chain lengths lead to some degree of unidirectional slip stacking. As pendant chain length is increased, trends show average layer offset increasing to a maximum of 2.07 Å in C5COFand then decreasing as chain length is extended through C11COF. Counterintuitively, shorter chains (C2–C4) give rise to lower yields of weakly crystalline materials, while longer chains (C6–C9) produce greater yields of highly crystalline materials, as confirmed by powder X-ray diffraction and scanning electron microscopy. Molecular dynamics simulations corroborate these observations, suggesting that long alkyl chains can interact favorably to promote the self-assembly of sheets. In situ proton NMR spectroscopy provides insights into the reaction equilibrium as well as the relationship between low COF yields and low crystallinity. These results provide fundamental insights into principles of supramolecular assembly in 2D COFs, demonstrating an opportunity for harnessing favorable side-chain interactions to produce highly crystalline materials.

Two-dimensional lead halide perovskites offer numerous attractive features for optoelectronics owing to their soft, deformable lattices and high degree of chemical tunability. While alteration of the metal and halide ions gives rise to significant modification of the bandgap energy, the organic spacer cations offer in-roads to tuning phase behavior and more subtle functionalities in ways that remain to be understood. Here, we study six variations of 2D perovskites changing only the organic spacer cations and demonstrate that these components intrinsically impact material response in important ways such as altering crystallographic structure, temperature-induced phase transitions, and photoluminescence emission. Two-dimensional perovskites containing commonly utilized aliphatic linear spacers, such as butylammonium, undergo phase transitions near room temperature. These transitions and temperature changes induce spacer-dependent variations in the emission spectra. Conversely, 2D perovskites comprising cyclic aliphatic spacers, such as cyclobutylammonium, are found to lack first-order phase transitions. These cyclic molecules are more sterically hindered within the crystal lattice, leading to temperature-induced contraction or expansion along certain crystallographic planes but no other significant thermal effects; additionally, they undergo changes in their emission spectra that cannot be explained by simple thermal expansion. Given the similarities in the dielectric and chemical makeup of this set of six alkylammonium molecules, these results are unexpected and suggest a large structural and thermal phase space via spacer manipulation that could lead to improved 2D perovskite functionalization.

Entropy-engineered materials are garnering considerable attention owing to their excellent mechanical and transport properties, such as their high thermoelectric performance. However, understanding the effect of entropy on thermoelectrics remains a challenge. In this study, we used the PbGeSnCdxTe3+xfamily as a model system to systematically investigate the impact of entropy engineering on its crystal structure, microstructure evolution, and transport behavior. We observed that PbGeSnTe3crystallizes in a rhombohedral structure at room temperature with complex domain structures and transforms into a high-temperature cubic structure at ∼373 K. By alloying CdTe with PbGeSnTe3, the increased configurational entropy lowers the phase-transition temperature and stabilizes PbGeSnCdxTe3+xin the cubic structure at room temperature, and the domain structures vanish accordingly. The high-entropy effect results in increased atomic disorder and consequently a low lattice thermal conductivity of 0.76 W m–1K–1in the material owing to enhanced phonon scattering. Notably, the increased crystal symmetry is conducive to band convergence, which results in a high-power factor of 22.4 μW cm–1K–1. As a collective consequence of these factors, a maximum ZTof 1.63 at 875 K and an average ZTof 1.02 in the temperature range of 300–875 K were obtained for PbGeSnCd0.08Te3.08. This study highlights that the high-entropy effect can induce a complex microstructure and band structure evolution in materials, which offers a new route for the search for high-performance thermoelectrics in entropy-engineered materials.

We report three new mixed-anion two-dimensional (2D) compounds: SrFPbBiS3, SrFAg0.5Bi1.5S3, and Sr2F2Bi2/3S2. Their structures as well as the parent compound SrFBiS2were refined using single-crystal X-ray diffraction data, with the sequence of SrFBiS2, SrFPbBiS3, and SrFAg0.5Bi1.5S3defining the new homologous series SrFMnBiSn+2(M = Pb, Ag0.5Bi0.5; n= 0, 1). Sr2F2Bi2/3S2has a different structure, which is modulated with a qvector of 1/3b* and was refined in superspace group X2/m(0β0)00 as well as in the 1 × 3 × 1 superstructure with space group C2/m(with similar results). Sr2F2Bi2/3S2features hexagonal layers of alternating [Sr2F2]2+and [Bi2/3S2]2–, and the modulated structure arises from the unique ordering pattern of Sr2+cations. SrFPbBiS3, SrFAg0.5Bi1.5S3, and Sr2F2Bi2/3S2are semiconductors with band gaps of 1.31, 1.21, and 1.85 eV, respectively. The latter compound exhibits room temperature red photoluminescence at ∼700 nm.

Superionic conductors possess liquid-like ionic diffusivity in the solid state, finding wide applicability from electrolytes in energy storage to materials for thermoelectric energy conversion. Type I superionic conductors (for example, AgI, Ag2Se and so on) are defined by a first-order transition to the superionic state and have so far been found exclusively in three-dimensional crystal structures. Here, we reveal a two-dimensional type I superionic conductor, α-KAg3Se2, by scattering techniques and complementary simulations. Quasi-elastic neutron scattering and ab initio molecular dynamics simulations confirm that the superionic Ag+ions are confined to subnanometre sheets, with the simulated local structure validated by experimental X-ray powder pair-distribution-function analysis. Finally, we demonstrate that the phase transition temperature can be controlled by chemical substitution of the alkali metal ions that compose the immobile charge-balancing layers. Our work thus extends the known classes of superionic conductors and will facilitate the design of new materials with tailored ionic conductivities and phase transitions.

Two-dimensional (2D) hybrid lead iodide perovskites have gained prominence due to their remarkable structural tunability, optoelectronic features, and moisture stability, which have rendered them as attractive alternatives to 3D MAPbI3for optoelectronic devices. 2D multilayer lead bromide perovskites remain an unfathomed phase space with the lack of systematic studies to establish the structure, photophysical properties and stability behavior of this family of 2D halide perovskites. Herein, we present new members of bilayer lead bromide perovskites (CmH2m+1NH3)2(CH3NH3)Pb2Br7(m= 6–8) that belong to the Ruddlesden–Popper structure type, incorporating long chain alkyl-monoammonium cations (CmH2m+1NH3) of hexylammonium (m= 6), heptylammonium (m= 7), and octylammonium (m= 8). A universal solution synthetic methodology for bulk multilayer lead bromide perovskites is presented with all structures solved and refined using single crystal X-ray diffraction. The studied bilayer lead bromide perovskites demonstrate a decrease in the lattice rigidity and lattice match of the inorganic perovskite layer–organic layer, as the alkyl-monoammonium chain length increases. In comparison to their iodide analogues, the bilayer lead bromide compounds exhibit elongation of their stacking axis despite the smaller dimensions of the [PbBr6]4−lattice, while their internal lattice strain was calculated to be reduced, inferring a greater lattice match between the inorganic [PbBr6]4−perovskite layer and organic layer. The (CmH2m+1NH3)2(CH3NH3)Pb2Br7(m= 4, 6–8) compounds exhibit narrow-band emission near 2.5 eV. Time-resolved photoluminescence (PL) displays longer carrier lifetimes on the nanosecond time scale comparing to their iodide analogues, where electronic structure calculations indicate that the increase of the alkyl chain length and, thus, lattice softness enhances nonradiative recombinations. A complete set of air, light, and heat stability tests on unencapsulated thin films of (CmH2m+1NH3)2(CH3NH3)Pb2Br7(m= 4, 6–8) and MAPbBr3show they are stable in ambient air for at least 5 months, exhibiting greater extrinsic stability than the 2D lead iodide congeners. Extraordinarily, 3D MAPbBr3films prove to be more stable than films of 2D lead bromide perovskites, in contrast to MAPbI3which is less stable than the 2D lead iodide perovskites.

Layered heterostructure materials with two different functional building blocks can teach us about emergent physical properties and phenomena arising from interactions between the layers. We report intergrowth compounds KLaM1 – xTe4(M= Mn and Zn; x≈ 0.35) featuring two chemically distinct alternating layers [LaTe3] and [KM1 – xTe]. Their crystal structures are incommensurate, determined by single X-ray diffraction for the Mn compound and a transmission electron microscope study for the Zn compound. KLaMn1 – xTe4crystallizes in the orthorhombic superspace group Pmnm(01/2γ)s00 with lattice parameters a= 4.4815(3) Å, b= 21.6649(16) Å, and c= 4.5220(3) Å. It exhibits charge density wave order at room temperature with a modulation wave vector q= 1/2b* + 0.3478c* originating from electronic instability of Te-square nets in [LaTe3] layers. The Mn analog exhibits a cluster spin glass behavior with spin freezing temperature Tf≈ 5 K attributed to disordered Mn vacancies and competing magnetic interactions in the [Mn1 – xTe] layers. The Zn analog also has charge density wave order at room temperature with a similar q-vector having the c* component ∼0.346 confirmed by selected-area electron diffraction. Electron transfer from [KM1 – xTe] to [LaTe3] layers exists in KLaM1 – xTe4, leading to an enhanced electronic specific heat coefficient. The resistivities of KLaM1 – xTe4(M= Mn and Zn) exhibit metallic behavior at high temperatures and an upturn at low temperatures, suggesting partial localization of carriers in the [LaTe3] layers with some degree of disorder associated with the Matom vacancies in the [M1 – xTe] layers.

A series of mixed-anion copper chalcogenides have been prepared using solid-state methods including ACu4.2TeS2(A = K, Rb, Cs), which adopt the KCu4S3structure type. The mixed-anion motif has an expanded sublattice, relative to KCu4S3, that can accommodate additional Cu atoms at its interstitial sites that are unoccupied in the parent structure. The variable temperature transport shows that the materials are p-type metals with carrier densities on the order of 1021cm–3and room-temperature electrical conductivity as high as 4000 S cm–1. Band structures calculated using density functional theory corroborate the experimental data and indicate that the interstitial Cu atoms lower the carrier concentration and increase the Fermi level of the materials. The layered structure has Te and S atoms occupying unique sites within the ACu4.2TeS2structure, where relatively hard S2-anions prefer Wyckoff positions where they can form energetically favorable acid–base interactions with hard alkali cations. The phenomenon is observed in the related K3Cu8Te2S4system, which also has a fully ordered layered structure. We believe that the report provides new chemical guidelines for targeting ordered multianion structures, as well as a unique method for tuning the electronic properties of metallic chalcogenides.

Standard solid-state methods produced black crystals of the compounds BaCu0.43(3)Te2and BaAg0.77(1)Te2at 1173 K; the crystal structures of each were established using single-crystal X-ray diffraction data. Both crystal structures are modulated. The compound BaCu0.43(3)Te2crystallizes in the monoclinic superspace group P2(αβ1/2)0, having cell dimensions of a= 4.6406(5) Å, b= 4.6596(5) Å, c= 10.362(1) Å, β = 90.000(9)°, and Z= 2 and an incommensurate vector of q= 0.3499(6)b* + 0.5c*. The compound BaAg0.77(1)Te2crystallizes in the orthorhombic P21212(α00)000 superspace group with cell dimensions of a= 4.6734(1) Å, b= 4.6468(1) Å, c= 11.1376(3) Å, and Z= 2 and an incommensurate vector of q= 0.364(2)a*. The asymmetric unit of the BaCu0.43(3)Te2structure comprises eight crystallographically independent sites; that for BaAg0.77(1)Te2comprises four. In these two structures, each of the M (M = Cu, Ag) atoms is connected to four Te atoms to make two-dimensional layers of [MxTe4/4]n−that are separated by layers of Ba atoms and square nets of Te. A Raman spectroscopic study at 298(2) K on a pelletized polycrystalline sample of BaAg0.8Te2shows the presence of Ag–Te (83, 116, and 139 cm–1) and Ba–Te vibrations (667 and 732 cm–1). A UV–vis–NIR spectroscopic study on a powdered sample of BaAg0.8Te2shows the semiconducting nature of the compound with a direct band gap of 1.0(2) eV, consistent with its black color. DFT calculations give a pseudo bandgap with a weak value of the DOS at the Fermi level.

Subchalcogenides are uncommon compounds where the metal atoms are in unusually low formal oxidation states. They bridge the gap between intermetallics and semiconductors and can have unexpected structures and properties because of the exotic nature of their chemical bonding as they contain both metal–metal and metal–main group (e.g., halide, chalcogenide) interactions. Finding new members of this class of materials presents synthetic challenges as attempts to make them often result in phase separation into binary compounds. We overcome this difficulty by utilizing indium as a metal flux to synthesize large (millimeter scale) single crystals of novel subchalcogenide materials. Herein, we report two new compounds Ir2In8Q (Q = Se, Te) and compare their structural and electrical properties to the previously reported Ir2In8S analogue. Ir2In8Se and Ir2In8Te crystallize in the P42/mnmspace group and are isostructural to Ir2In8S, but also have commensurately modulated (with qvectors q= 1/6a* + 1/6b* and q= 1/10a* + 1/10b* for Ir2In8Se and Ir2In8Te, respectively) low-temperature phase transitions, where the chalcogenide anions in the channels experience a distortion in the form of In–Q bond alternation along the abplane. Both compounds display re-entrant structural behavior, where the supercells appear on cooling but revert to the original subcell below 100 K, suggesting competing structural and electronic interactions dictate the overall structure. Notably, these materials are topological semimetal candidates with symmetry-protected Dirac crossings near the Fermi level and exhibit high electron mobilities (∼1500 cm2V–1s–1at 1.8 K) and moderate carrier concentrations (∼1020cm–3) from charge transport measurements. This work highlights metal flux as a synthetic route to high quality single crystals of novel intermetallic subchalcogenides with Dirac semimetal behavior.

A new ternary telluride, Ba3ScTe5, with a pseudo-one-dimensional structure, was synthesized at 1173 K by standard solid-state methods. A single-crystal X-ray diffraction study at 100(2) K shows the structure to be modulated. The structure of the subcell of Ba3ScTe5crystallizes with two formula units in the hexagonal space group D6h3–P63/mcmwith unit cell dimensions of a= b= 10.1190(5) Å and c= 6.8336(3) Å. The asymmetric unit of the subcell structure consists of four crystallographically independent sites: Ba1 (site symmetry: m2m), Sc1 (−3.m), Te1 (m2m), and Te2 (3.2). Its structure is made up of chains of ∞1[ScTe33–] that are separated by Ba2+cations. The Sc atoms are bonded to six Te1 atoms that form a slightly distorted octahedral geometry. The structure of the subcell also contains linear infinite chains of Te2 with intermediate Te···Te interactions. The superstructure of Ba3ScTe5is incommensurate and was solved in the hexagonal superspace group P–6(00γ)0 with a= 10.1188(3) Å and c= 6.8332(3) Å and a modulation vector of q= 0.3718(2)c*. The arrangement and coordination geometries of the atoms in the superstructure are very similar to those in the substructure. However, the main difference is that the infinite chains of Te atoms in the superstructure are distorted owing to the formation of long- and short-bonded pairs of Te atoms. The presence of these chains with intermediate Te···Te interactions makes assignment of the formal oxidation states arbitrary. The optical absorption study of a polycrystalline sample of Ba3ScTe5that was synthesized by the stoichiometric reaction of elements at 1173 K reveals a direct band gap of 1.1(2) eV. The temperature-dependent resistivity study of polycrystalline Ba3ScTe5shows semiconducting behavior corroborating the optical studies, while density functional theory calculations report a pseudo band gap of 1.3 eV.

The halide perovskite Ruddlesden–Popper (RP) phases are a homologous layered subclass of solution-processable semiconductors that have aroused great attention, especially for developing long-term solar photovoltaics. They are defined as (A′)2(A)n−1PbnX3n+1(A′ = spacer cation, A = cage cation, and X = halide anion). The orientation control of low-temperature self-assembled thin films is a fundamental issue associated with the ability to control the charge carrier transport perpendicular to the substrate. Here we report new chemical derivatives designed from a molecular perspective using a novel spacer cation 3-phenyl-2-propenammonium (PPA) with conjugated backbone as a low-temperature strategy to assemble more efficient solar cells. First, we solved and refined the crystal structures of single crystals with the general formula (PPA)2(FA0.5MA0.5)n−1PbnI3n+1(n= 2 and 3, space group C2) using X-ray diffraction and then used the mixed halide (PPA)2(Cs0.05(FA0.88MA0.12)0.95)n−1Pbn(I0.88Br0.12)3n+1analogues to achieve more efficient devices. While forming the RP phases, multiple hydrogen bonds between PPA and inorganic octahedra reinforce the layered structure. For films we observe that as the targeted layer thickness index increases from n= 2 to n= 4, a less horizontal preferred orientation of the inorganic layers is progressively realized along with an increased presence of high-nor 3D phases, with an improved flow of free charge carriers and vertical to substrate conductivity. Accordingly, we achieve an efficiency of 14.76% for planar p–i–n solar cells using PPA-RP perovskites, which retain 93.8 ± 0.25% efficiency with encapsulation after 600 h at 85 °C and 85% humidity (ISOS-D-3).

The introduction of large-volume amines (LVAs) in Sn-based perovskite films has been shown to lead to promising power conversion efficiency (PCE) in Pb-free perovskite solar cells (PSCs). However, the LVAs adopted so far (e.g., phenylethylammonium [PEA] and butylammonium [BA]) are insulating and could impede charge extraction within the perovskite film. Herein, a conjugated LVA, 3-phenyl-2-propen-1-amine (PPA), is introduced in formamidinium tin iodide (FASnI3) perovskite. Our results show that the incorporation of PPA results in enlarged grain sizes, reduced trap density, preferential orientation, efficient charge extraction, and enhanced structural stability of FASnI3film. These positive effects help in achieving efficient PSCs with a PCE as high as 9.61% with negligible hysteresis and outstanding stability (remains 92% of its initial PCE value after 1,440 h). Furthermore, the presence of PPA enables a self-healing action of PSCs. Most importantly, we report large-area (1 × 1 cm2) Sn-based PSCs achieving PCE of 7.08%.

Engendering electrical conductivity in otherwise insulating metal–organic framework (MOF) materials is key to rendering these materials fully functional for a range of potential applications, including electrochemical and photo-electrochemical catalysis. Here we report that the platform MOF, NU-1000, can be made electrically conductive via reversible electrochemical oxidation of a fraction of the framework’s tetraphenylpyrene linkers, where the basis for conduction is redox hopping. At a microscopic level, redox hopping is akin to electron self-exchange and is describable by Marcus’ well-known theory of electron transfer. At a macroscopic level, the hopping behavior leads to diffusive charge transport and is quantifiable as an apparent diffusion coefficient, Dhopping. Theory suggests that the csqtopology of NU-1000, together with its characteristic one-dimensional mesopores, will result in direction-dependent, that is, anisotropic, electrical conductivity. Detailed computations suggest that the governing factor is the strength of electronic coupling between pairs of linkers sited in the a,bplane of the MOF versus the mesopore-aligned caxis of the crystal. The notion has been put to the test experimentally by configuring the MOF as an array of selectively oriented, electrode-supported crystallites, where the rodlike crystallites are either oriented largely normal to the electrode (requiring redox hopping along the cdirection) or mainly parallel (requiring redox hopping mainly through the a,bplane). The orientations are preselected by preparing MOF films either via interfacial solvothermal synthesis or via electrophoretic deposition. In semiquantitative accord with computational predictions, Dhoppingis up to ∼3500 times larger in the cdirection than through the a,bplane. In addition to their fundamental significance, the findings have clear implications for the design and optimization of MOFs for electrocatalysis and for other applications that rely upon electrical conductivity.