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RESEARCH SUMMARY

My goal is to apply sustainable synthesis and advanced manufacturing techniques in the development of a new, cost-effective catalyst with superior performance for environmental remediation, utilising nanoporous materials. Through this work, I aim to address pressing global challenges and support the United Nations' Sustainable Development Goals, with a focus on achieving clean energy (Goal 7), reducing plastic waste (Goal 12), and mitigating global warming (Goal 13).

Main Research Areas:

  • Porous materials synthesis and characterisation

  • Synthesis of hierarchical porous materials using green and scalable synthetic approaches

  • Innovative catalyst technologies using functional porous materials 

  • Energy conversion and storage using hierarchical porous materials

research summary

One of my key scientific contributions was the development of a low-solvent, more environmentally-friendly synthesis route for the production of copper-based MOF catalysts with hierarchical porosity. I have developed a new method using supercritical CO2 (scCO2) as a time- and material-efficient route to MOF synthesis with a high level of control over the crystallization process for accessing tailored material properties. I also made significant intellectual contributions to the development of intelligent scalable synthetic methods to produce additional large pores in defective MOF structures which were shown to be highly beneficial for their catalytic activity. The impact of this approach on heterogeneous catalysis was that these new MOFs with hierarchical porosity delivered an enhanced performance with fast intercalation of reactants into active sites. 

Furthermore, my experience in using sustainable synthetic approaches has allowed me to achieve the economical production of nanomaterials. For instance, I have demonstrated the development of nanocomposites with novel heterostructures using cheap resources such as plastic waste and natural halloysite, for example, producing multifunctional AgInS2@MIL-101(Cr) and O-g-C3N4@MIL-53(Fe) materials with enhanced porosity via a facile preparation, Co-Fe-BTC/CN nanocomposite with bimetallic structures via a microwave-assisted hydrothermal method and Ag@AgBr/Al-SBA-15, Ag-g-C3N4@HNT and V2O5/Al-SBA-15 with semiconductor-containing porous structures via a one-pot and green synthetic approach. The novel nanocomposites were shown to improve the activity of visible-light-driven catalysts for the efficient treatment of multiple toxic pollutants in water. This could allow wastes to be transformed into economically valuable materials again and protect wildlife and the environment from further pollution. 

RESEARCH BLOGS


MOF in acid etching

Introducing hierarchical pore structure to microporous materials such as metal-organic frameworks (MOFs) can be beneficial for reactions where the rate of reaction is limited by low rates of diffusion or high pressure drop. This advantageous pore structure can be obtained by defect formation, mostly via post-synthetic acid etching, which has been studied extensively on water-stable MOFs. Here we show that a water-unstable HKUST-1 MOF can also be modified in a corresponding manner by using phosphoric acid as a size-selective etching agent and a mixture of dimethyl sulfoxide and methanol as a dilute solvent. Interestingly, we demonstrate that the etching process which is time- and acidity- dependent, can result in formation of defective HKUST-1 with extra interconnected hexagonal macropores without compromising on the bulk crystallinity. These findings suggest an intelligent scalable synthetic method for formation of hierarchical porosity in MOFs that are prone to hydrolysis, for improved molecular accessibility and diffusion for catalysis.

gas sorption of defective MOF

Figure. Nitrogen isotherms of HKUST-1 etching in phosphoric acid using DMSO and MeOH as dilute solvents at different concentrations (a) and times (b). The full isotherms in logarithmic scale in the blown-up sections show 2-stepped adsorption in the samples, which correspond to two different micropores preserved after etching.

This work was published in Scientific Reports 9, 10887 (2019)

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macroporous MOF

Introduction of multiple pore size regimes into metal-organic frameworks (MOFs) to form hierarchical porous structures can lead to improved performance of the material in various applications. In many cases, where interactions with bulky molecules are involved, enlarging the pore sizes of typically microporous MOF adsorbents or MOF catalysts is crucial for enhancing both mass transfer and molecular accessibility. In this review, we examine the range of synthetic strategies which have been reported thus far to prepare hierarchical MOFs or MOF composites with added macroporosity. These fabrication techniques can be either pre- or post-synthetic and include use of structural templating agents, gelation, defect formation, routes involving supercritical CO2 and 3D printing. We also discuss some challenges involved in the current techniques, which must be addressed if any of these approaches are to be taken forward for large-scale application.

This review was published in Nano-Micro Letters 11, 54 (2019)

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hierarchical MOF

It is shown that a crystalline metal-organic framework (HKUST-1) can be rapidly synthesized from DMSO/MeOH solution with greatly reduced amounts of organic solvents using a supercritical CO2 (scCO2) solvent expansion technique. The precursor solution is stable for months under ambient conditions, and CO2-driven MOF crystallization is achieved under mild conditions (40˚C, 40-100 bar) with excellent reproducibility. As the degree of liquid phase expansion drives MOF nucleation and growth, the crystallite size and overall yield can be tuned by adjusting the CO2 pressure. Furthermore, scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM) and gas sorption analyses showed that in the presence of scCO2, HKUST-1 crystallites with a hierarchical pore structure are generated through a post-crystallization etching process. These findings demonstrate that scCO2 is a time and material efficient route to MOF synthesis with a high level of control over the crystallization process for accessing tailored material properties.

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