Regulating electron transfer and orbital interaction within metalloporphyrin-MOFs for highly sensitive NO2 sensing.

The understanding of electron transfer pathways and orbital interactions between analytes and adsorption sites in gas-sensitive studies, especially at the atomic level, is currently limited. Herein, we have designed eight isoreticular catechol-metalloporphyrin scaffolds, FeTCP-M and InTCP-M (TCP = 5,10,15,20-tetrakis-catechol-porphyrin, M = Fe, Co, Ni and Zn) with adjustable charge transfer schemes in the coordination microenvironment and precise tuning of orbital interactions between analytes and adsorption sites, which can be used as models for exploring the influence of these factors on gas sensing. Our experimental findings indicate that the sensitivity and selectivity can be modulated using the type of metals in the metal-catechol chains (which regulate the electron transfer routes) and the metalloporphyrin rings (which fine-tune the orbital interactions between analytes and adsorption sites). Among the isostructures, InTCP-Co demonstrates the highest response and selectivity to NO2 under visible light irradiation, which could be attributed to the more favorable transfer pathway of charge carriers in the coordination microenvironment under visible light illumination, as well as the better electron spin state compatibility, higher orbital overlap and orbital symmetry matching between the N-2s2pz hybrid orbital of NO2 and the Co-3dz2 orbital of InTCP-Co.

Pseudotetrahedral Organotin-Capped Chalcogenidometalate Supermolecules with Optical Limiting Performance.

The rational design of crystalline clusters with adjustable compositions and dimensions is highly sought after but quite challenging as it is important to understand their structural evolution processes and to systematically establish structure-property relationships. Herein, a family of organotin-based sulfidometalate supertetrahedral clusters has been prepared via mixed metal and organotin strategies at low temperatures (60-120 °C). By engineering the metal composition, we can effectively control the size of the clusters, which ranges from 8 to 35, accompanied by variable configurations: P1-[(RSn)4M4S13], T3-[(RSn)4In4M2S16] (R = nbutyl-Bu and phenyl-Ph; M = Cd, Zn, and Mn), T4-[(BuSn)4In13Cu3S31], truncated P2, viz. TP2-[(BuSn)6In10Cu6S31], and even T5-[(BuSn)4In22Zn6Cu3S52], all of which are the largest organometallic supertetrahedral clusters known to date. Of note, the arylstannane approach plays a critical role in regulating the peripheral ligands and further enriching geometric structures of the supertetrahedral clusters. This is demonstrated by the formation of tin-oxysulfide clusters, such as T3-[(RSn)4Sn6O4S16] (R = Bu, Ph, and benzyl = Be) and its variants, truncated T3, viz., TT3-[(BuSn)6Sn3O4S13] and augmented T3, viz., T3-[(Bu3SnS)4Sn6O4S16]. Especially, two extraordinary truncated clusters break the tetrahedral symmetry observed in typical supertetrahedral clusters, further substantiating the advantages offered by the arylstannane approach in expanding cluster chemistry. These organometallic supertetrahedral clusters are highly soluble and stable in common solvents. Additionally, they have tunable third-order nonlinear optical behaviors by controlling the size, heterometallic combination, organic modification, and intercluster interaction.

Multilevel-Regulated Metal-Organic Framework Platform Integrating Pore Space Partition and Open-Metal Sites for Enhanced CO2 Photoreduction to CO with Nearly 100% Selectivity.

Rational design and regulation of atomically precise photocatalysts are essential for constructing efficient photocatalytic systems tunable at both the atomic and molecular levels. Herein, we propose a platform-based strategy capable of integrating both pore space partition (PSP) and open-metal sites (OMSs) as foundational features for constructing high-performance photocatalysts. We demonstrate the first structural prototype obtained from this strategy: pore-partitioned NiTCPE-pstp (TCPE = 1,1,2,2-tetra(4-carboxylphenyl)ethylene, pstp = partitioned stp topology). Nonpartitioned NiTCPE-stp is constructed from six-connected [Ni3(µ3-OH)(COO)6] trimer and TCPE linker to form 1D hexagonal channels with six coplanar OMSs directed at channel centers. After introducing triangular pore-partitioning ligands, half of the OMSs were retained, while the other half were used for PSP, leading to unprecedented microenvironment regulation of the pore structure. The resulting material integrates multiple advanced properties, including robustness, wider absorption range, enhanced electronic conductivity, and high CO2 adsorption, all of which are highly desirable for photocatalytic applications. Remarkably, NiTCPE-pstp exhibits excellent CO2 photoreduction activity with a high CO generation rate of 3353.6 µmol g-1 h-1 and nearly 100% selectivity. Theoretical and experimental studies show that the introduction of partitioning ligands not only optimizes the electronic structure to promote the separation and transfer of photogenerated carriers but also reduces the energy barrier for the formation of *COOH intermediates while promoting CO2 activation and CO desorption. This work is believed to be the first example to integrate PSP strategies and OMSs within metal-organic framework (MOF) photocatalysts, which provides new insight as well as new structural prototype for the design and performance optimization of MOF-based photocatalysts.

Superhydrophobic Pseudosupertetrahedral Sulfido Metalate Clusters for Constructing Liquid Marbles.

One pseudopentasupertetrahedral chalcogenidometalate cluster, [(BuSn)3SnCd4S13(OH)]·6(H+DMP) (PPS-1; H+DMP = protonated 3,5-dimethylpiperidine), has been isolated by use of an organotin precursor. They are arranged to generate two types of tetrahedrally patterned cages, which further interconnect to form a diamond network. Owing to the covalent attachment of abundant alkyl groups, PPS-1 exhibits excellent hydrophobicity and could be used as an assembly substance for building liquid marbles.

Accurate binding of porous aluminum molecular ring catalysts with the substrate.

Metal molecular rings are a class of compounds with aesthetically pleasing symmetry and fundamentally useful properties. The reported work generally focuses on the ring center cavity, and there is little known about those on the ring waist. Herein, we report the discovery of porous aluminum molecular rings and their performance and contribution to the cyanosilylation reaction. We develop a facile ligand induced aggregation and solvent regulation strategy towards AlOC-58NC and AlOC-59NT with high purity, high yield (75% and 70%, respectively) and gram-level scale-up. These molecular rings exhibit a "two-tier" pore feature involving the general central cavity and newly observed equatorial semi-open cavities. AlOC-59NT with two types of one-dimensional channels showed good catalytic activity. The interaction of the aluminum molecular ring catalyst with the substrate has been crystallographically characterized and theoretically confirmed, showing a ring adaptability process that involves the capture and binding of the substrate. This work provides new ideas for the assembly of porous metal molecular rings and to understand the overall reaction pathway involving aldehydes and is expected to inspire the design of low-cost catalysts through structural modifications.

Thiophenol-spaced 2D coordination polymers with extraordinary alkali resistance and efficient photothermal conversion.

Coordination polymers (CPs) based on metal-sulfur bonds are rare; we herein realize a series of thiol-functionalized linker-based CPs (thiol-CPs), MTBT (M = Fe, Co and Zn; TBT = dehydrated 4,4'-thiobisbenzenethiol), which feature an anionic two-dimensional (2D) network, [M(TBT)2]n2n-, with the tetrahedral coordination unit {MS4} serving as a node. These compounds exhibit excellent hydrolytic stability, especially in alkaline solution (20M NaOH for five days), which is the highest value reported for CPs so far. In addition, among them, CoTBT displays favorable photo-thermal conversion effectiveness under an energy power of 0.5 W cm-2 808 nm laser irradiation for 15 s, with the temperature rising rapidly from room temperature to 135.2 °C.

Modification of metallic and non-metallic sites in pentasupertetrahedral chalcogenidometalate clusters for third-order nonlinear optical response.

Four isomorphic P2 chalcogenide clusters named [Sn11In9Cu6S44]·11(H+DBU) (1) (DBU = 1,8-diazabicyclo[5.4.0] undec-7-ene), [Sn10In10Cu6Se44]·6(H22+DMAPA)·2(DMAPA)·9EG (2) (DMAPA = 3-dimethylaminopropylamine, EG = ethylene glycol), [Sn10In10Cu6S40O4]·6[H22+PMDETA]·10EG (3) (PMDETA = pentamethyldiethylenetriamine), [Sn10Ga10Cu6S40O4]·6(H22+DMAPA)·7EG (4) have been isolated via organotin precursor and mixed-metal strategy. These clusters exhibit excellent solubility in organic solvents. The continuous-regulation of optical band and optical limiting performance have been realized through precise controlled substituting engineering of cationic and anionic elements.

Energy Band Alignment and Redox-Active Sites in Metalloporphyrin-Spaced Metal-Catechol Frameworks for Enhanced CO2 Photoreduction.

Two new chemically stable metalloporphyrin-bridged metal-catechol frameworks, InTCP-Co and FeTCP-Co, were constructed to achieve artificial photosynthesis without additional sacrificial agents and photosensitizers. The CO2 photoreduction rate over FeTCP-Co considerably exceeds that obtained over InTCP-Co, and the incorporation of uncoordinated hydroxyl groups, associated with catechol, into the network further promotes the photocatalytic activity. The iron-oxo coordination chain assists energy band alignment and provides a redox-active site, and the uncoordinated hydroxyl group contributes to the visible-light absorptance, charge-carrier transfer, and CO2 -scaffold affinity. With a formic acid selectivity of 97.8 %, FeTCP-OH-Co affords CO2 photoconversion with a reaction rate 4.3 and 15.7 times higher than those of FeTCP- Co and InTCP-Co, respectively. These findings are also consistent with the spectroscopic study and DFT calculation.

Construction of Titanium-Based Metal-Organic Frameworks Based on the Ti/Cu Heteronuclear Cluster.

Presented here are two titanium-based metal-organic frameworks (Ti-MOFs) based on well-defined [Ti6Cu6(µ3-O)2(µ2-O)9(HSO4)2(SO4)6], which can be easily obtained from a cheap Ti source and CuSO4 and exhibited interesting magnetic properties. Furthermore, this clusters can be isolated in pure phase. Numerous uncoordinated sites of SO4 and labile ligands on the Ti and Cu centers of this cluster make it a good candidate as a secondary building unit to construct various Ti-MOFs in the future.

Understanding the Efficiency and Selectivity of Two-Electron Production of Metalloporphyrin-Embedded Zirconium-Pyrogallol Scaffolds in Electrochemical CO2 Reduction.

Because of the high efficiency and mild reaction conditions, electrocatalytic CO2 reduction (ECR) has attracted significant attention in recent years. However, the specific mechanism of the formation of the two-electron production (CO or HCOOH) in this reaction is still unclear. Herein, with density functional theory calculation and experimental manipulation, the specific mechanism of the selective two-electron reduction of CO2 has been systematically investigated, employing the polyphenolate-substituted metalloporphyrinic frameworks, ZrPP-1-M (M = Fe, Co, Ni, Cu, and Zn), as model catalysts. Experimental observations and theoretical calculations discovered that ZrPP-1-Co is a more favorable catalyst for ECR among them. Compared with the formation of HCOOH, electroreduction of CO2 into CO has more beneficial thermodynamic and kinetic routes with ZrPP-1-Co as a catalyst. After introducing the r-GO for improving the conductivity, the Faradaic efficiency for CO formation is 82.4% at -0.6 v (vs RHE).

Photochemical In Situ Exfoliation of Metal-Organic Frameworks for Enhanced Visible-Light-Driven CO2 Reduction.

Two novel two-dimensional metal-organic frameworks (2D MOFs), 2D-M2 TCPE (M=Co or Ni, TCPE=1,1,2,2-tetra(4-carboxylphenyl)ethylene), which are composed of staggered (4,4)-grid layers based on paddlewheel-shaped dimers, serve as heterogeneous photocatalysts for efficient reduction of CO2 to CO. During the visible-light-driven catalysis, these structures undergo in situ exfoliation to form nanosheets, which exhibit excellent stability and improved catalytic activity. The exfoliated 2D-M2 TCPE nanosheets display a high CO evolution rate of 4174 µmol g-1 h-1 and high selectivity of 97.3 % for M=Co and Ni, and thus are superior to most reported MOFs. The performance differences and photocatalytic mechanisms have been studied with theoretical calculations and photoelectric experiments. This study provides new insight for the controllable synthesis of effective crystalline photocatalysts based on structural and morphological coregulation.

Tin-oxychalcogenide supertetrahedral clusters maintained in a MTN zeolite-analog arrangement by coulombic interactions.

Two crystalline salts, T3-SnOX-MTN (X = S/Se, MTN denotes a defined zeotype), both spatially assembled in an MTN net, have been fabricated. This was achieved by interlinking the isolated tin-oxychalcogenide tetrahedrally shaped clusters of T3-[Sn10O8X16]8- (X = S/Se) through coulombic interactions with protonated organic amine templates. T3-SnOX-MTN (X = S/Se), with 74.1/76.5 Å cubic unit-cell axial-lengths, have a proton-conductivity of over 10-3 S cm-1 under 98% relative humidity at 50 °C.

Elucidating J-Aggregation Effect in Boosting Singlet-Oxygen Evolution Using Zirconium-Porphyrin Frameworks: A Comprehensive Structural, Catalytic, and Spectroscopic Study.

Metal-organic frameworks (MOFs) are powerful toolkits to directly correlate structure-function relationships due to their well-defined structures. In this work, 5,15-di(3,4,5-trihydroxyphenyl)porphyrin (DTPP) and 5,10,15,20-tetra(3,4,5-trihydroxyphenyl)porphyrin (TTPP) are reacted with zirconium ions to afford two MOFs (Zr-DTPP and Zr-TTPP) with acid and base tolerance in the pH range of 1.0-14.0. Powder X-ray diffraction investigation combined with Rietveld refinement reveals the J-aggregated porphyrin building blocks confined by benzene-1,2,3-trisolate-zirconium chains in the newly prepared Zr-DTPP. Electron spin-resonance, singlet-oxygen determination, and sulfides oxidation experiments demonstrate a much better singlet-oxygen evolution of J-aggregated Zr-DTPP than that of unaggregated Zr-TTPP reported previously, in good contrast to the weaker photocatalytic capability disclosed for DTPP than that for TTPP in solution, consummating the theory of photosensitizer J-aggregation in boosting heterogeneous photoinduced singlet-oxygen generation.

A wide pH-range stable crystalline framework based on the largest tin-oxysulfide cluster [Sn20O10S34].

We report, herein, a diamond-like oxysulfide framework, 3D-T4-SnOS, based on the largest supertetrahedral cluster of Sn4+ ions, i.e. [Sn20O10S34]. The framework remains intact in aqueous solution over a pH range between 1 and 14, and has a narrower optical bandgap, red-shifted fluorescence emission, and an enhanced photoelectric response compared to that of the smaller version, 2D-T3-SnOS, which has a building unit of supertetrahedral [Sn10O4S20].

Robust Porphyrin-Spaced Zirconium Pyrogallate Frameworks with High Proton Conduction.

An isoreticular family of zirconium polyphenolate networks (ZrPP- n, n = 1 and 2), bridged by porphyrinic macrocycles in an eclipsed arrangement, have excellent stability toward water, especially strong basic media of saturated NaOH aqueous solution. Endowed with spatial alignment of protic sites, viz., partially protonated phenols of acidity enhanced by coordination to Zr4+, along with guest dimethylamine cations, the newly synthesized ZrPP- n reveal exceptional conductivity (8.0 × 10-3 and 4.2 × 10-3 S cm-1, for n = 1 and 2, respectively, pelleted sample, under 98% relative humidity at 25 °C).

Dual-cubic-cage based lanthanide sulfate-carboxylpyrazolate frameworks with high hydrolytic stability and remarkable proton conduction.

We report herein a series of lanthanide sulfate-carboxylpyrazolate frameworks based on double cuboid cavities that are highly hot-water stable, and have room-temperature proton conductivity of over 10-3 S cm-1 at 97% relative humidity without any appreciable loss of performance for at least three recycling times, ranking among the best lanthanide-based coordination frameworks.

Robust multivariate metal-porphyrin frameworks for efficient ambient fixation of CO2 to cyclic carbonates.

A family of multivariate metal-organic frameworks (MOFs) with three-kinds of orderly distributed metals were designed and successfully synthesized by combining metalloporphyrin sheets and pentafluoride (NbOF5)2- pillars. Benefiting from the cooperative nature of open-metal-sites (OMSs) within porphyrins, specific pore-sizes, coupled with fluorine-rich electrostatic environments, the fabricated materials demonstrated high affinity toward CO2, and good catalytic performance, structural robustness, and good recyclability for the conversion of epoxides and CO2 to cyclic carbonates at room temperature and 1 atm pressure.

Charge- and Size-Complementary Multimetal-Induced Morphology and Phase Control in Zeolite-Type Metal Chalcogenides.

Zeolite-type chalcogenides are desirable due to their integration between porosity and semiconductivity. CPM-120, with super-sodalite topology (Zeolite Structure Code: RWY), is among the few zeolite-type chalcogenides with permanent porosity, and is the only chalcogenide with a zeolite code. Importantly, the RWY-type has evolved into a platform for studying properties of porous chalcogenides. Yet so far, few studies have been made to probe the effects of synthetic parameters and framework compositions on this platform. Here, we probe the effects of the third metal type (Ga3+ , In3+ , Cd2+ , and Sn4+ ) on the Zn2+ /Ge4+ /S2- platform. We find that charge-complementary and size-compatible Ga3+ leads to the synthesis of CPM-120-ZnGaGeS which is the first trimetallic zeolite-type chalcogenide, with improved crystal morphology and reproducibility. We also find that charge-compatible and size-complementary cations (Cd2+ or Sn4+ ) can induce an abrupt phase transition from super-sodalite to super-diamond, also with unprecedented trimetallic T2 clusters. For In3+ , which is dual-complementary (charge and size), a gradual phase transition is observed with increasing In3+ amount. Furthermore, by controlling the cluster composition, tunable band gaps can be realized. These materials show promising properties such as high CO2 uptake (4.32 mmol cm-3 , 298 K, 1 bar) and high photocatalytic activity.

Acid and Base Resistant Zirconium Polyphenolate-Metalloporphyrin Scaffolds for Efficient CO2 Photoreduction.

A series of zirconium polyphenolate-decorated-(metallo)porphyrin metal-organic frameworks (MOFs), ZrPP-n (n = 1, 2), featuring infinite ZrIV -oxo chains linked via polyphenolate groups on four peripheries of eclipse-arranged porphyrin macrocycles, are successfully constructed through a top-down process from simulation to synthesis. These are the unusual examples of Zr-MOFs (or MOFs in general) based on phenolic porphyrins, instead of commonly known carboxylate-based types. Representative ZrPP-1 not only exhibits strong acid resistance (pH = 1, HCl) but also remains intact even when immersed in saturated NaOH solution (≈20 m), an exceptionally large range of pH resistance among MOFs. The metallation at the porphyrin core gives rise to materials with enhanced sorption and catalytic properties. In particular, ZrPP-1-Co, with precise and uniform distribution of active centers, exhibits not only high CO2 trapping capability (≈90 cm3 g-1 at 1 atm, 273 K, among the highest in Zr-MOFs) but also high photocatalytic activity for reduction of CO2 into CO (≈14 mmol g-1 h-1 ) and high selectivity over CH4 (>96.4%) without any cocatalyst under visible-light irradiation (λ > 420 nm). Given the strong chemical resistance under extreme alkali conditions, these catalysts can be recycled without appreciable loss of activity. The possible mechanism for photocatalytic reduction of CO2 -to-CO over ZrPP-1-Co is also proposed.

Integrating Zeolite-Type Chalcogenide with Titanium Dioxide Nanowires for Enhanced Photoelectrochemical Activity.

Developing photoanodes with efficient visible-light harvesting and excellent charge separation still remains a key challenge in photoelectrochemical water splitting. Here zeolite-type chalcogenide CPM-121 is integrated with TiO2 nanowires to form a heterostructured photoanode, in which crystalline CPM-121 particles serve as a visible light absorber and TiO2 nanowires serve as an electron conductor. Owing to the small band gap of chalcogenides, the hybrid electrode demonstrates obvious absorption in visible-light range. Electrochemical impedance spectroscopy (EIS) shows that electron transport in the hybrid electrode has been significantly facilitated due to the heterojunction formation. A >3-fold increase in photocurrent is observed on the hybrid electrode under visible-light illumination when it is used as a photoanode in a neutral electrolyte without sacrificial agents. This study opens up a new avenue to explore the potential applications of crystalline porous chalcogenide materials for solar-energy conversion in photoelectrochemistry.