Xinle Li Lab
Nanoporous Functional Materials for Energy and Environment
Our research group is focused on the development of crystalline porous materials including metal-organic frameworks (MOFs), covalent organic frameworks (COFs) and their derived composites for energy and environmental applications such as heterogeneous catalysis, environmental remediation as well as green synthesis of crystalline porous materials.
I. Advanced Crystalline Porous Materials Synthesis
Covalent organic frameworks (COFs) represent an emerging paradigm for crystalline porous materials that reticulate organic monomers into two or three-dimensional (2D or 3D) extended networks and have been in the limelight of organic materials chemistry since 2005. In a radical deviation from amorphous covalently linked porous materials, COFs possess unmatchable structural exclusivities such as high crystallinity, permanent porosity, lightweight character, versatile synthesis, and modular pore metrics, which underpin their applications in a plethora of areas including gas adsorption, separation, sensing, environmental remediation, therapeutics, and optoelectronics.
However, their fullest exploitation is being hindered by a magnitude of barriers:
(1) inherent chemical instability rooted in the reversible covalent linkages of COFs;
(2) sluggish synthesis that creates substantial obstacles for their accelerated discoveryï¼›
(3) limited structures of COFs relative to their cousin materials, metal-organic frameworks (MOFs, > 90,000 structures);
(4) poor processability and insufficient hierarchical porosity of COF powders compromising their practical utility;
(5) elusive mechanistic insight into the formation of new COFs beyond imine and boronate ester linkages.
To address these issues, we will establish a versatile synthetic toolkit for producing numerous new COFs through integrated synthesis, characterization, application and simulation feedback loops, which enables transformative research at the interface of COF chemistry, polymer science, organic material crystallization, computational simulations, and energy/environmental applications.
We would like to (1) develop a versatile toolkit that empowers the rapid and green synthesis of COFs with extraordinary stability and tailor-made architectures, simultaneously boosting both chemical stability and structural complexity of COFs; (2) delineatee a facile avenue toward flexible hierarchical COF-based composites with tailorable properties such as wettability and stimuli-responsiveness, which mitigate the unprocessable issue of COFs and thus promote their real-world applications in a plethora of domains; (3) advance conceptual understandings of the synthetic process through clear monomer-COF correlations, which will streamline the synthetic processes of new COFs; (4) provide a rare and panoramic view of ether COF assembly processes, which underpins the predictive synthesis of next-generation COFs.
Representative articles (CAU):
Precision Chemistry, 2023, 1, 233–240.
Green Chemistry, 2023, 25, 6287-6296
ACS Sustainable Chemistry & Engineering, 2024 ,12, 13535-13543
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Representative articles (Prior to CAU):
II. Heterogeneous Catalysis in Covalent-Organic Frameworks
As the metal-free counterpart of MOFs, COFs have skeletal structure linked via strong covalent bonds rather than coordinate bonds that comprise MOFs. Moreover, the presence of hydrogen bonding and pi–pi stacking interaction in COFs further strengthens the skeletal and pore structure and protects them from solvation and hydrolysis. In comparison with inorganic zeolites and porous silica materials, COFs have higher porosity and bigger and tunable pore size which speed up the diffusion of reactants and desorption of products, thereby promoting higher yield and selectivity. Moreover, COFs exhibit ultrahigh theoretical specific surface area and high chemical stability which renders them as an ideal heterogeneous catalyst.
III. Environmental Remediation by Orderly Porous Frameworks
The quality of human life is directly influenced by the nature of the local environment. Access to fresh water has been recognized as an essential component to realize human rights fully. The United Nations estimates suggest the global population to reach ∼10 billion by the year 2050. Thus, the requirement of freshwater is expected to cause tremendous stress on the existing sources. In addition, the growing industrialization and agricultural activities across the globe bestow significant stress by virtue of emitting large amounts of wastewater. Thus, the treatment and safe disposal of effluents is a pressing concern and necessitates urgent attention.
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Among the different methods tested for the removal of organic pollutants, adsorption-based protocols have received enormous attention on account of cost, simplicity, and energy considerations. The development of novel materials or composites as sorbents for these applications has attracted remarkable research attention in recent years. In particular, porous materials have been frontrunners in the research in this regard, owing to access to high surface areas, higher capacities, and the inclusion of specific functional sites.
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Representative articles (CAU):
Precision Chemistry, 2023, 1, 233–240.
Green Chemistry, 2023, 25, 6287-6296
​
Conventionally, the research in the domain of porous solids has been limited to zeolites and activated carbons. Since the advent of crystalline coordination polymers and the subsequent emergence of MOFs and COFs, the scope and span of porous solids have enlarged substantially. The application of orderly porous materials still presents many challenges in the efficient elimination of pollutants in real applications in a large scale, such as the reusability, price, processability, selectivity under complicated conditions, and separation from wastewater. Such problems will be resolved with the development of technology in the future. We believe that COF-based materials will have huge prospect in environmental pollution management.
Funding
