Synthesis, Characterization, and Catalytic Performance of Metal-Organic Frameworks Derived from Pristine and Functionalized Ligands for CO2 Reduction and Hydrogen Evolution Reactions

Project Abstract

Synthesis, characterization, and catalytic performance of a series of metal-organic frameworks (MOFs) derived from pristine and functionalized ligands were investigated to address CO2 reduction and hydrogen evolution reactions (HER) under ambient and simulated electrochemical conditions. The study integrates a rational design approach, leveraging modulated solvothermal synthesis to tailor pore architecture, metal node geometry, and functional group density to optimize CO2 adsorption, activation, and proton-electron transfer pathways. A library of Ln/transition metal-based MOFs incorporating rigid multi-dentate ligands with electron-donating and -withdrawing substituents was synthesized, followed by systematic post-synthetic modifications to introduce catalytically active sites and to tune hydrophilicity/hydrophobicity balance within the pore environment. Comprehensive characterization employed single-crystal and powder X-ray diffraction, Fourier-transform infrared spectroscopy, solid-state NMR, thermogravimetric analysis, scanning and transmission electron microscopy, and porosimetry to elucidate crystallinity, thermal stability, surface area, and defect concentrations. Elemental analysis and X-ray photoelectron spectroscopy provided oxidation state information and metal–ligand coordination environments, while in situ spectroelectrochemical measurements probed real-time changes in electronic structure during catalytic cycles. Electrochemical performance for CO2 reduction was evaluated in CO2-saturated dimethylformamide and aqueous media using a three-electrode setup, with a focus on selectivity toward CO, formate, and multi-carbon products, and on suppression of competing hydrogen evolution. For HER, linear sweep voltammetry and rotating disk electrode measurements quantified overpotential, Tafel slopes, exchange current densities, and stability over extended chronoamperometry tests. The functionalized MOFs demonstrated enhanced CO2 uptake due to tailored pore apertures and strong chemisorption at introduced amine, pyridine, or imidazole moieties, facilitating CO2 activation and subsequent electron transfer to proximal catalytic centers. Post-synthetic metalation and defect engineering generated coordinatively unsaturated sites and localized Lewis acidity/basicity, creating synergistic active-site ensembles that lowered energy barriers for key intermediates such as CO2•?, COOH*, and HCOO* in CO2RR, as well as optimized proton delivery for HER. Comparative analysis against pristine-ligand MOFs highlighted the pivotal role of ligand electronics and linker rigidity in dictating mass transport, product distribution, and long-term catalyst durability. In situ Raman and X-ray absorption spectroscopy traced intermediate species and oxidation state cycling, confirming a dual-site mechanism with cooperative BI–OB interactions between metal nodes and functionalized linkers. Density functional theory calculations complemented experimental findings by mapping adsorption energies, reaction coordinates, and charge transfer pathways, guiding further ligand derivatization for targeted product selectivity. The integrated framework demonstrates that judicious combination of pristine and functionalized ligands in MOFs can break conventional trade-offs between activity, selectivity, and stability for CO2RR and HER, offering scalable routes to hybrid catalysts with tunable performance for sustainable energy conversion.

Project Overview

What This Project Is About

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The project looks at tiny, highly organized structures called metal-organic frameworks (MOFs). These are built from metal parts linked by organic connectors (ligands). The study compares MOFs made from pristine ligands with those made from functionalized (chemically modified) ligands to see how changes affect their ability to help convert carbon dioxide (CO2) into useful chemicals and to produce hydrogen gas, both of which are important for clean energy and reducing greenhouse gases.

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The Problem It Addresses

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CO2 levels are rising and sustainable energy is needed. Many catalysts used for CO2 reduction and hydrogen evolution are not efficient, selective, or stable enough. MOFs offer tunable structures that could improve performance, but it is not yet clear which ligand designs work best for these specific reactions. This project investigates that gap.

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Objectives of the Project

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1. Compare pristine versus functionalized ligands in MOFs for CO2 reduction.
2. Assess hydrogen evolution reaction performance of the MOFs.
3. Characterize structure, stability, and surface properties of the MOFs.
4. Identify which ligand features correlate with better catalytic activity.

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What You Will Do Step by Step

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1. Synthesize MOFs using standard solvothermal methods with different ligands.
2. Characterize materials (structure, composition, surface area) using common lab techniques.
3. Test catalytic activity for CO2 reduction and hydrogen evolution in setup simulations.
4. Analyze product distribution and efficiency; compare pristine vs functionalized MOFs.
5. Interpret data to relate ligand changes to performance trends.

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Expected Outcome

Expect to identify which ligand modifications enhance catalytic activity, stability, and selectivity for CO2 reduction and hydrogen evolution, providing design rules for better MOF catalysts and potential pathways for scalable clean energy solutions.