Xiaolei Fan

Underlying mechanism of the hydrothermal instability of Cu3(BTC)2 metal-organic framework

Water induced decomposition of Cu3(BTC)2 (BTC = benzene-1,3,5-tricarboxylate) metal-organic framework (MOF) was studied using dynamic water vapour adsorption. Small-angle X-ray scattering, Fourier transform infrared spectroscopy and differential scanning calorimetry analyses revealed that the underlying mechanism of Cu3(BTC)2 MOF decomposition under humid streams is the interpenetration of water molecules into Cu-BTC coordination to displace organic linkers (BTC) from Cu centres.

Assessment of MOF’s Quality: Quantifying Defect Content in Crystalline Porous Materials

A quantitative method for assessment of defects in metal-organic framework (MOF) is presented based on isotherms calculated using Grand Canonical Monte Carlo (GCMC) simulations. Defects in MOF structures generated during the synthesis and sample preparation can lead to large variations in experimentally measured adsorption isotherms but are difficult to quantify. We use as a case study CO2 adsorption on Cu3(BTC)2 MOF (BTC = benzene-1,3,5-tricarboxylic acid) to show that different samples reported in the literature have various proportions of principal pores blocked or side pores blocked, resulting in isotherms with different capacity and affinity toward CO2. The approach presented is easily generalized to other materials, showing that simulation results combined with experimentally measured gas adsorption isotherms can be used to quantitatively identify key defective features of the material.

Pd/C catalysts based on synthetic carbons with bi- and tri-modal pore-size distribution: applications in flow chemistry

Two new types of phenolic resin-derived synthetic carbons with bi-modal and tri-modal pore-size distributions were used as supports for Pd catalysts. The catalysts were tested in chemoselective hydrogenation and hydrodehalogenation reactions in a compact multichannel flow reactor. Bi-modal and tri-modal micro-mesoporous structures of the synthetic carbons were characterised by N2 adsorption. HR-TEM, PXRD and XPS analyses were performed for characterising the synthesised catalysts. N2 adsorption revealed that tri-modal synthetic carbon possesses a well-developed hierarchical mesoporous structure (with 6.5 nm and 42 nm pores), contributing to a larger mesopore volume than the bi-modal carbon (1.57 cm3 g−1versus 1.23 cm3 g−1). It was found that the tri-modal carbon promotes a better size distribution of Pd nanoparticles than the bi-modal carbon due to presence of hierarchical mesopore limitting the growth of Pd nanoparticles. For all the model reactions investigated, the Pd catalyst based on tri-modal synthetic carbon (Pd/triC) show high activity as well as high stability and reproducibility. The trend in reactivities of different functional groups over the Pd/triC catalyst follows a general order alkyne ≫ nitro > bromo ≫ aldehyde.

Design of 2D materials for selective adsorption: a comparison between Monte Carlo simulations and direct numerical integration

Understanding the behaviour of fluids in confinement is essential to predict adsorption selectivity and develop adsorbents that can address challenging separations, such as ethane/ethylene mixtures. In this work we show that adsorption selectivity for an ethane/ethylene mixture can be predicted from direct numerical integration of the solid–fluid interaction potential because fluid–fluid interactions are negligible when compared to solid–fluid interactions, and adsorption sites are indistinguishable in pure component and mixture simulations. We present a comprehensive analysis of the density and orientation distributions in the pores as a function of pore size and pressure, providing tools that can be used for the design of 2D materials for the selective adsorption of gases.

On improving the hydrogen and methanol production using an auto-thermal double-membrane reactor: Model prediction and optimisation

Abstract The concentric configured thermally-coupled double-membrane reactor (TCDMR) was optimised to improve the co-production of hydrogen and methanol. Using a detailed approach, we identified the non-linear differential evolution (DE) algorithm as the most suitable optimisation tool among the most used optimisation algorithms in reactor design (GA, PSO, and DE) due to its ability to converge to the optimal solution with fewer iterations. Considering DE algorithm with the industry benchmark data, we optimised the key operational parameters of TCDMR (as OTCDMR), leading to the improved reactor performance (regarding the overall heat transfer and methanol/hydrogen production) compared to the conventional methanol reactor (CMR) and TCDMR. Simulation results show that the methanol production rate of OTCDMR could reach 315.7 tonnes day−1, representing a 22.6% enhancement than CMR (257 tonnes day−1). For the hydrogen production, OTCDMR is predicted to deliver 19.7 tonnes of hydrogen per day, surpassing the 15.5 tonnes day−1 production rate by TCDMR.

Understanding the CO Oxidation on Pt Nanoparticles Supported on MOFs by Operando XPS

Metal‐organic frameworks (MOFs) are playing a key role in developing the next generation of heterogeneous catalysts. In this work, near ambient pressure X‐ray photoelectron spectroscopy (NAP‐XPS) is applied to study in operando the CO oxidation on Pt@MOFs (UiO‐67) and Pt@ZrO2 catalysts, revealing the same Pt surface dynamics under the stoichiometric CO/O2 ambient at 3 mbar. Upon the ignition at ca. 200 °C, the signature Pt binding energy (BE) shift towards the lower BE (from 71.8 to 71.2 eV) is observed for all catalysts, confirming metallic Pt nanoparticles (NPs) as the active phase. Additionally, the plug‐flow light‐off experiments show the superior activity of the Pt@MOFs catalyst in CO oxidation than the control Pt@ZrO2 catalyst with ca. 28 % drop in the T50% light‐off temperature, as well as high stability, due to their sintering‐resistance feature. These results provide evidence that the uniqueness of MOFs as the catalyst supports lies in the structural confinement effect.