Atomic Layer Deposition of Rhenium-Aluminum Oxide Thin Films and ReOx Incorporation in a Metal-Organic Framework

Thermal atomic layer deposition of rhenium nitride and rhenium metal thin films using methyltrioxorhenium

The growth of rhenium nitride and rhenium metal thin films is presented using atomic layer deposition (ALD) with the precursors methyltrioxorhenium and 1,1-dimethylhydrazine. Saturative, self-limiting growth was determined at 340 °C for pulse times of ≥4.0 s for methyltrioxorhenium and ≥0.1 s for 1,1-dimethylhydrazine. An ALD window was observed from 340 to 350 °C with a growth rate of about 0.60 Å per cycle. Films grown at 340 °C revealed a root mean square surface roughness of 2.7 nm for a 70 nm thick film and possessed a composition of ReN_0.14 with low O and C content of 1.6 and 2.6 at%, respectively. Enhanced nucleation on in situ grown TiN, relative to thermal SiO₂, enabled a conformality of 98% on high aspect ratio trenched structures. Subjecting the ReN_0.14 thin films to thermal or chemical and thermal treatments reduced the nitrogen content to ≤1.6 at%, yielding a film purity of about 96 at% rhenium and resistivities as low as 51 μΩ cm. The Re metal film thicknesses on the trenched structures remained intact during the post-deposition annealing treatments and the films did not delaminate from the substrate surfaces.

Atomic layer deposition of ternary ruthenates by combining metalorganic precursors with RuO4 as the co-reactant

In this work, the use of ruthenium tetroxide (RuO₄) as a co-reactant for atomic layer deposition (ALD) is reported. The role of RuO₄ as a co-reactant is twofold: it acts both as an oxidizing agent and as a Ru source. It is demonstrated that ALD of a ternary Ru-containing metal oxide (i.e. a metal ruthenate) can be achieved by combining a metalorganic precursor with RuO₄ in a two-step process. RuO₄ is proposed to combust the organic ligands of the adsorbed precursor molecules while also binding RuO₂ to the surface. As a proof of concept two metal ruthenate processes are developed: one for aluminum ruthenate, by combining trimethylaluminum (TMA) with RuO₄; and one for platinum ruthenate, by combining MeCpPtMe₃ with RuO₄. Both processes exhibit self-limiting surface reactions and linear growth as a function of the number of ALD cycles. The observed saturated growth rates are relatively high compared to what is usually the case for ALD. At 100 °C sample temperature, growth rates of 0.86 nm per cycle and 0.52 nm per cycle are observed for the aluminum and platinum ruthenate processes, respectively. The TMA/RuO₄ process results in a 1 : 1 Al to Ru ratio, while the MeCpPtMe₃/RuO₄ process yields a highly Ru-rich composition with respect to Pt. Carbon, hydrogen and fluorine impurities are present in the thin films with different relative amounts for the two investigated processes. For both processes, the as-deposited films are amorphous.

Pyrene-based metal organic frameworks: from synthesis to applications

Pyrene is one of the most widely investigated aromatic hydrocarbons given to its unique optical and electronic properties. Hence, pyrene-based ligands have been attractive for the synthesis of metal-organic frameworks (MOFs) in the last few years. In this review, we will focus on the most important characteristics of pyrene, in addition to the development and synthesis of pyrene-based molecules as bridging ligands to be used in MOF structures. We will summarize the synthesis attempts, as well as the post-synthetic modifications of pyrene-based MOFs by the incorporation of metals or ligands in the structure. The discussion of promising results of such MOFs in several applications; including luminescence, photocatalysis, adsorption and separation, heterogeneous catalysis, electrochemical applications and bio-medical applications will be highlighted. Finally, some insights and future prospects will be given based on the studies discussed in the review. This review will pave the way for the researchers in the field for the design and development of novel pyrene-based structures and their utilization for different applications.

Active metal single-sites based on metal–organic frameworks: construction and chemical prospects

Metal single-point is a novel and potential design strategy that has been applied for the development of metal organic frameworks.

Metal-Organic Framework-Based Catalysts with Single Metal Sites

Metal-organic frameworks (MOFs) are a class of distinctive porous crystalline materials constructed by metal ions/clusters and organic linkers. Owing to their structural diversity, functional adjustability, and high surface area, different types of MOF-based single metal sites are well exploited, including coordinately unsaturated metal sites from metal nodes and metallolinkers, as well as active metal species immobilized to MOFs. Furthermore, controllable thermal transformation of MOFs can upgrade them to nanomaterials functionalized with active single-atom catalysts (SACs). These unique features of MOFs and their derivatives enable them to serve as a highly versatile platform for catalysis, which has actually been becoming a rapidly developing interdisciplinary research area. In this review, we overview the recent developments of catalysis at single metal sites in MOF-based materials with emphasis on their structures and applications for thermocatalysis, electrocatalysis, and photocatalysis. We also compare the results and summarize the major insights gained from the works in this review, providing the challenges and prospects in this emerging field.

The Synthesis Science of Targeted Vapor-Phase Metal-Organic Framework Postmodification

The postmodification of metal organic frameworks (MOFs) affords exceedingly high surface area materials with precisely installed chemical features, which provide new opportunities for detailed structure-function correlation in the field of catalysis. Here, we significantly expand upon the number of vapor-phase postmodification processes reported to date through screening a library of atomic layer deposition (ALD) precursors, which span metals across the periodic table and which include ligands from four distinct precursor classes. With a large library of precursors and synthesis conditions, we discern trends in the compatibility of precursor classes for well-behaved ALD in MOFs (AIM) and identify challenges and solutions to more precise postsynthetic modification.

Micromesoporous Nitrogen-Doped Carbon Materials Derived from Direct Carbonization of Metal-Organic Complexes for Efficient CO2 Adsorption and Separation

Metal-organic complexes (MOCs) are considered as excellent precursors to prepare carbon materials, due to the fact that heteroatoms and functional groups can be naturally reserved in the resulting carbon materials through the carbonization. Herein, micromesoporous nitrogen-doped carbons MPNC-1 and MPNC-2 are successfully obtained by direct carbonization (800 °C, KOH activation) of metal-organic complexes DQA-1 and DQA-2. MPNC-1 and MPNC-2 exhibit high BET surface area (2368.9 and 2327.6 m² g^-1), pore volume (1.95 and 1.89 cm³ g^-1), and N contents (17.2% and 12.3%). At 25 °C and 1 bar, MPNC-1 and MPNC-2 show high CO₂ adsorption of 7.53 and 6.58 mmol g^-1, the estimated CO₂/N₂ selectivity are 20.5 and 22.6, indicating excellent promise for practical CO₂ adsorption and separation applications. Theoretical calculation indicates carbon surfaces with pyridinic-N, pyrrolic-N, and graphitic-N coexistence could strongly change the local electronic distribution and electrostatic surface potential, enhancing the CO₂ adsorption with adsorption energy of -58.96 kJ mol g^-1. Theoretical calculation also highlights that CO₂ adsorption mechanism is electrostatic interaction with a large green isosurface between CO₂ molecules and the carbon surface.

Nitrogen-Doped Microporous Carbons Derived from Pyridine Ligand-Based Metal-Organic Complexes as High-Performance SO2 Adsorption Sorbents

Heteroatom-doped porous carbons are emerging as platforms for gas adsorption. Herein, N-doped microporous carbon (NPC) materials have been synthesized by carbonization of two pyridine ligand-based metal-organic complexes (MOCs) at high temperatures (800, 900, 1000, and 1100 °C). For NPCs (termed NPC-1- T and NPC-2- T, where T represents the carbonization temperature), the micropore is dominant, pyridinic-N and other N atoms of MOC precursors are mostly retained, and the N content reaches as high as 16.61%. They all show high Brunauer-Emmett-Teller surface area and pore volume, in particular, NPC-1-900 exhibits the highest surface areas and pore volumes, up to 1656.2 m² g^-1 and 1.29 cm³ g^-1, respectively, a high content of pyridinic-N (7.3%), and a considerable amount of SO₂ capture (118.1 mg g^-1). Theoretical calculation (int = ultrafine m062x) indicates that pyridinic-N acts as the leading active sites contributing to high SO₂ adsorption and that the higher content of pyridinic-N doping into the graphite carbon layer structure could change the electrostatic surface potential, as well as the local electronic density, which enhanced SO₂ absorption on carbon edge positions. The results show great potential for the preparation of microporous carbon materials from pyridine ligand-based MOCs for effective SO₂ adsorption.

Hot-Pressing Method To Prepare Imidazole-Based Zn(II) Metal-Organic Complexes Coatings for Highly Efficient Air Filtration

Particulate matters (PMs) air pollution has become a serious environmental issue due to its great threat to human health. Herein, metal-organic complexes PBM-Zn1 and PBM-Zn2 coatings (noted as PBM-Zn-Filter) have been produced by the hot-pressing method on various substrates for the first time. Layer-by-layer PBM-Zn-Filters were also obtained through varying hot-pressing cycles. The obtained PBM-Zn-Filters with high robustness show excellent performance in PMs removal. In particular, benefiting from thelarger conjugation system, micropore structure, lower pressure drop, higher electrostatic potential ζ, and electron cloud exposed metal center of PBM-Zn2 (DFT calculations), PBM-Zn2@melamine foam-4 gives the highest removal rates, PM2.5:99.5% ± 1.2% and PM10:99.3% ± 1.1%, and the removal efficiency for capture PM2.5 and PM10 particles in cigarette smoke were both retained at high levels (>95.5%) after 24 h tests. More importantly, a homemade mask is made up by imbedding the PBM-Zn2@melamine foam-4 into a commercial breathing mask, which shows higher removal efficiency, lower pressure drop, smaller thickness, and higher quality factor than two commercial breathing masks, the PMs removal efficiencies for both PM2.5 and PM10 are 99.6% ± 0.5% and 99.4% ± 0.8%, and acceptable air resistance are demonstrated.