Xu Li

In Situ Confinement of Ultrasmall Pd Clusters within Nanosized Silicalite-1 Zeolite for Highly Efficient Catalysis of Hydrogen Generation

Well-dispersed and ultrasmall Pd clusters in nanosized silicalite-1 (MFI) zeolite have been prepared under direct hydrothermal conditions using [Pd(NH2CH2CH2NH2)2]Cl2 as precursor. High-resolution scanning transmission electron microscopy studies indicate that the Pd clusters are encapsulated within the intersectional channels of MFI, and the Pd clusters in adjacent channels visually aggregate, forming nanoparticles (NPs) of ∼1.8 nm. The resultant catalysts show an excellent activity and highly efficient H2 generation toward the complete decomposition of formic acid (FA) under mild conditions. Notably, thanks to the further reduced Pd NP size (∼1.5 nm) and the additionally introduced basic sites, the Pd/S-1-in-K catalyst affords turnover frequency values up to 856 h(-1) at 25 °C and 3027 h(-1) at 50 °C. The easy in situ confinement synthesis of metal clusters in zeolites endows the catalysts with superior catalytic activities, excellent recyclability, and high thermal stability, thus opening new perspectives for the practical application of FA as a viable and effective H2 storage material for use in fuel cells.

An N-rich metal–organic framework with an rht topology: high CO2 and C2 hydrocarbons uptake and selective capture from CH4

We report the storage capacities and separation selectivity of an rht-type s-heptazine-based metal organic framework (MOF), [Cu3(TDPAH)(H2O)3]·13H2O·8DMA, 1, (where TDPAH is 2,5,8-tris(3,5-dicarboxylphenylamino)-s-heptazine and DMA is N,N-dimethylacetamide) for C2 hydrocarbons and CO2 over CH4. MOF 1 displays the highest C2H2/CH4 selectivity of 80.9 as well as record high C2H4 and C2H6 adsorption enthalpies. Theoretical calculations reveal that s-heptazine and NH groups within the framework have synergistic effects on CO2 binding.

Accelerated crystallization of zeolites via hydroxyl free radicals

Radically faster synthesis Zeolite synthesis normally proceeds under basic conditions that allow the oxide bridges between aluminum and silicon atoms to break and reform. Feng et al. show that the formation of hydroxyl radicals, either by irradiation with ultraviolet light or with the Fenton reagent, can speed up the formation of the crystallized zeolite by about a factor of 2. Science, this issue p. 1188 Hydroxyl radicals generated with ultraviolet light or Fenton reagents can approximately double the rate of zeolite synthesis. In the hydrothermal crystallization of zeolites from basic media, hydroxide ions (OH–) catalyze the depolymerization of the aluminosilicate gel by breaking the Si,Al–O–Si,Al bonds and catalyze the polymerization of the aluminosilicate anions around the hydrated cation species by remaking the Si,Al–O–Si,Al bonds. We report that hydroxyl free radicals (•OH) are involved in the zeolite crystallization under hydrothermal conditions. The crystallization processes of zeolites—such as Na–A, Na–X, NaZ–21, and silicalite-1—can be accelerated with hydroxyl free radicals generated by ultraviolet irradiation or Fenton’s reagent.

In silico prediction and screening of modular crystal structures via a high-throughput genomic approach

High-throughput computational methods capable of predicting, evaluating and identifying promising synthetic candidates with desired properties are highly appealing to todays scientists. Despite some successes, in silico design of crystalline materials with complex three-dimensionally extended structures remains challenging. Here we demonstrate the application of a new genomic approach to ABC-6 zeolites, a family of industrially important catalysts whose structures are built from the stacking of modular six-ring layers. The sequences of layer stacking, which we deem the genes of this family, determine the structures and the properties of ABC-6 zeolites. By enumerating these gene-like stacking sequences, we have identified 1,127 most realizable new ABC-6 structures out of 78 groups of 84,292 theoretical ones, and experimentally realized 2 of them. Our genomic approach can extract crucial structural information directly from these gene-like stacking sequences, enabling high-throughput identification of synthetic targets with desired properties among a large number of candidate structures.

Publisher Correction: Infused-liquid-switchable porous nanofibrous membranes for multiphase liquid separation

In Table 1 of this Article, the third row in the furthest right column contains a typographical error and should read ‘NH’, rather than ‘NM’, corresponding to n-hexane as the infused liquid.