Our Research

The widespread implementation of intermittent renewable energy sources such as solar and wind requires the efficient storage of electron equivalents. The development of methods to store energy via the generation of chemical fuels in a carbon-neutral fashion represents one strategy to address this issue. A major focus of our research is dedicated to the sequestration and catalytic reduction of stable substrates such as CO2 to commodity chemicals and energy-rich fuels. We are also interested in the upconversion of stable molecules and industrial waste products to value-added products.

Our work involves development and study of catalyst platforms based upon discrete organometallic complexes, nanoparticle assemblies, and heterogeneous interfaces that are then incorporated into thermal, photo- and electrocatalytic cycles. In addition to designing, preparing, and utilizing catalysts that range from coordination compounds to heterogeneous films, we also focus on understanding how the chemical and physical properties of surfaces and interfaces can be manipulated during catalytic processes to enable especially challenging bond making/breaking processes as summarized in this video.

Inspired by the extensive work over the last 70+ years to the synthesis and study of porphyrins, and related platforms for applications in light-harvesting and catalysis, we focus on the development of non-traditional tetrapyrrole architectures. Despite the ubiquitous use of porphyrins for photochemical applications, these traditional tetrapyrrole cofactors are limited in that they typically only engage in single-electron redox chemistry. By contrast, although much less stable porphyrinogens and related derivatives with reduced meso-carbons support multielectron properties needed to drive many important small molecule activation processes.

By adapting tetrapyrrole chemistry, we generate new platforms that effectively marry the photophysical and transition-metal coordination chemistry of porphyrins with the intriguing redox properties of porphyrinogens to produce families of non-aromatic tetrapyrroles (e.g., phlorins, biladienes, & isocorroles) that support a rich multielectron photochemistry. Such systems show great promise as platforms for energy storing cycles and small molecule activation. Reactions we currently target are applicable to energy and environmental sustainability, including the upconversion of common environmental pollutants, as well as the oxygen reduction reaction (O2 ➔ 2 H2O), which is important for the operation of air batteries and fuel cell devices.

Common cancer treatments (i.e., surgery/resection, radiation therapy, and chemo- or immunotherapy) have efficacies that vary depending on a cancer type and can suffer from significant negative side effects. A significant opportunity exists to develop new phototheranostics that can induce the formation of cytotoxic reactive oxygen species (ROS) such as singlet oxygen (PDT) or intense heat (PTT) for the treatment of a number of different cancers. Upon implementation of such strategies, a simple light source can be focused on a precise area (such as a tumor) to constrain the therapeutic treatment to the targeted tissue and minimize collateral damage and unwanted side effects.

We have placed major emphasis on development and study of metallated biladiene complexes for applications in photomedicine and cancer phototherapy. These complexes are well tolerated by biological systems and have low inherent toxicities but are potent photosensitizers of ROS that cause oxidative degradation of cellular components and vasculature, ultimately leading to tumor death. Accordingly, the platforms we develop allow us to use light to trigger tumor apoptosis, including in triple-negative breast cancer, which is particularly aggressive and challenging to treat.

In addition to our work to further tune the electronic structure and light absorbing properties of our tetrapyrrole systems, we also incorporate them within both inorganic and organic nanoparticle assemblies to enable tandem photothermal therapy (PTT) and other complementary light-based strategies to administer therapeutics with high spaciotemporal resolution. These efforts involve significant collaboration with our colleagues in the Department of Biomedical Engineering and elsewhere on UD’s campus.

Porous materials are important to many fields and industries. In recent years, the preparation and study of metal-organic frameworks (MOFs) has been very important for applications relating to small molecule separation, storage, sensing and activation. While MOF synthesis using very high-temperature forcing conditions has been a topic of much investigation, these methods are either incompatible or deliver poor quality 3-D materials based on metals in certain oxidation states and thermally sensitive organic bridging units. Similar limitations exist for the synthesis of complex organic molecules in which existing thermal transformations do not always provide requisite levels of synthetic control.

To address these limitations, we are developing strategies and methods to drive the synthesis of porous materials (such as MOFs and molecular cages) and complex organic molecules using electricity as opposed to heat. This work provides access to materials and compounds that either cannot be readily accessed via traditional high-temperature methods or whose preparation is not possible using thermal chemistries. Our electrosynthesis work sits at the interfaces of electrochemistry and materials synthesis, and organic reaction development and involves collaboration with several other research groups in our department and across our campus.