Synthesis and characterization of metal-organic frameworks (MOFs) for selective CO2 capture and catalytic conversion to cyclic carbonates under ambient conditions

Project Abstract

The escalating concentration of atmospheric CO2 necessitates innovative, sustainable strategies for capture and valorization that operate under ambient conditions. This study reports the design, synthesis, and comprehensive characterization of a series of metal-organic frameworks (MOFs) engineered for high CO2 uptake, selective adsorption in the presence of competing gases, and efficient catalytic conversion of CO2 to cyclic carbonates via cycloaddition reactions with epoxides. Rational linker selection and metal node combinations were employed to tune pore size, surface functionality, and Lewis acid–base sites to optimize CO2 affinity and activation. MOFs incorporating soft Lewis acidic centers (e.g., Zn2+, Cu2+, and Zn4 clusters) were functionalized with pendant amine and sulfonate groups to enhance CO2 binding through chemisorption pathways while maintaining rapid diffusion kinetics. Synthesis protocols were optimized to achieve high crystallinity, controlled defect density, and scalable production, with post-synthetic modification used to introduce catalytic sites that promote CO2 epoxidation and subsequent cycloaddition. Comprehensive physicochemical characterization included X-ray diffraction for structural confirmation, N2 and CO2 sorption isotherms to determine surface area and pore size distribution, thermogravimetric analysis for thermal stability, and Fourier-transform infrared spectroscopy to monitor functional group incorporation. Gas adsorption studies revealed selective CO2 uptake at ambient pressure (0–1 bar) with high CO2/N2 selectivity, attributable to size-exclusion effects and favorable CO2–framework interactions. In situ spectroscopic measurements and solid-state NMR provided insights into adsorption mechanisms, indicating a combination of physisorption and chemisorption at active sites. Density functional theory calculations supported experimental observations by correlating electronic structure with adsorption energetics and identifying the most active coordinative environments for CO2 activation. Catalytic activity was evaluated through cycloaddition of CO2 with various epoxides under ambient temperature and pressure, with turnover frequencies and selectivities quantified to establish structure–activity relationships. The best-performing MOF demonstrated rapid conversion, high selectivity toward cyclic carbonates, and significant stability over multiple reuse cycles, underscoring its practical potential for CO2 valorization. Mechanistic studies suggested a cooperative mechanism wherein the MOF’s Lewis acidic centers activate CO2 while nucleophilic co-catalysts or framework-bound functionalities promote ring-opening and cyclization steps. Control experiments with pristine porous organic cages and homogeneous catalysts highlighted the advantages of the heterogeneous MOF framework, including recyclability and reduced product contamination. A holistic assessment of material performance, including regeneration energy, synthesis scalability, and compatibility with real-world flue gas compositions, was conducted to evaluate practical applicability. The results establish a viable platform where MOFs function both as efficient CO2 sorbents and as heterogeneous catalysts for converting captured CO2 to cyclic carbonates under ambient conditions, offering a dual approach to mitigating atmospheric CO2 while enabling value-added chemical synthesis.

Project Overview

What This Project Is About

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This project looks at creating and studying tiny, porous crystals called metal-organic frameworks (MOFs) that can capture carbon dioxide (CO2) from the air or exhaust streams and then help turn that CO2 into useful cyclic carbonates. It focuses on doing these tasks under normal, or ambient, conditions without harsh equipment.

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The Problem It Addresses

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Rising CO2 levels contribute to climate change, and current capture methods can be expensive or energy-intensive. Many catalytic processes to convert CO2 into useful chemicals require high pressures or temperatures. This project aims to find MOFs that both trap CO2 efficiently and drive its conversion to cyclic carbonates at room temperature, offering a simpler and greener approach.

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Objectives of the Project

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1. Understand how MOFs interact with CO2 at a basic level.
2. Prepare a set of MOFs with different pore sizes and chemical environments.
3. Test CO2 capture efficiency under ambient conditions.
4. Evaluate the catalytic activity of MOFs for turning CO2 into cyclic carbonates.
5. Characterize the structure and properties of the MOFs before and after reactions.

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What You Will Do Step by Step

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1. Review simple literature on MOFs and CO2 chemistry.
2. Synthesize a small library of MOFs using safe, beginner-friendly procedures.
3. Characterize materials with basic techniques (e.g., surface area, pore size, and structure).
4. Expose MOFs to CO2 to measure capture capacity at room temperature.
5. Perform tests to see if CO2 can be converted into cyclic carbonates under ambient conditions.
6. Analyze products with straightforward methods and compare results across MOFs.
7. Discuss how MOF structure relates to performance and outline limitations.

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Expected Outcome

Expect to identify one or more MOFs that combine good CO2 uptake with catalytic activity at room temperature, along with clear data on how pore structure influences performance. The project should yield practical insights for low-energy CO2 capture and conversion strategies and provide a basis for future improvements.