(7dc) Vapor-Phase Deposition for Functional Metal-Organic Framework (MOF) and Polymer Thin Films

Recent chemical attacks in Syria have caused many civilian casualties. The nerve agent sarin used in these incidents is a kind of highly toxic organophosphorus compounds that can paralyze human central nerve systems and rapidly lead to severe injuries and deaths. The threat of these chemical warfare agents (CWAs) motivates the development of new materials for protecting soldiers, first-responders and the public. Current state-of-the-art filters are based on impregnated activated carbon and do not have catalytic activity for destructing CWAs. In contrast, metal-organic frameworks (MOFs) have been reported with exceptional catalytic performance and are therefore promising candidates for decontamination applications. Integrating thin films of MOFs with textiles could enable protective garments and masks.

It is nontrivial to form conformal and continuous MOF thin films on polymer fiber surfaces, since conventional synthesis methods often lead to sparse crystals on fibers. My Ph.D. research was mainly focused on developing new approaches to enhance MOF thin film growth on fibers,^1–4 investigating MOF-functionalized fibers for defense-related applications,^1,2,4 and searching for rapid reaction routes to synthesize MOF and MOF-based composites at room temperature for future manufacturing.³ We have demonstrated that atomic layer deposited (ALD) metal oxide layers enhance the heterogeneous nucleation of MOFs on fiber surfaces, enable the formation of uniform, continuous and high quality MOF thin films, and significantly improves the mass loading and adhesion of MOFs to the fiber substrates.^1,2,4 Our MOF-functionalized nonwoven fiber mats and electrospun nanofibers exhibit large adsorption capacity for hazardous gases such as NH₃ and H₂S,^1–3 and high catalytic activity for degrading CWA simulants and nerve agents in minutes.⁴ These results all indicate that our MOF-coated textiles are very promising for the next generation of protective masks and suits. To push forward the industrial applications and commercialization of MOF-based materials, we developed a new synthesis method using hydroxy double salts (HDS) as key intermediates for rapid formation of MOFs and MOF thin films in just 1 minute. The ultra-high space-time-yield (up to 2.9×10⁴ kg∙m^-3∙d^-1 for Cu-BTC powder) shows the great potential of our process for scaling up MOF manufacturing.³

In addition to the research achievements highlighted above, I have also investigated CO₂ diffusion in mm-scale Cu-BTC crystals (collaboration with Vanderbilt University),⁵ studied the growth mechanism and kinetics of MOF thin films using in situ ATR-FTIR with a flow cell (collaboration with NIST), and applied ALD for synthesis and modification of nanostructures. Currently, I am investigated initiated chemical vapor deposited (iCVD) polymer thin films for desalination-related applications at MIT.⁶ In the future, I will actively explore functional thin film materials for applications in energy, environment and artificial intelligence.

Teaching Interests:

My teaching interest falls in reaction kinetics and chemical reactor design courses for both undergraduate and graduate students, which will be well supported by my past experience as a teaching assistant for undergraduate chemical reaction engineering classes. I am also interested in designing a course to introduce chemical processes involved in advanced nano-manufacturing, based on my research and work experience in semiconductor industry. My past experience in mentoring undergraduate and graduate students will also be beneficial for teaching.

(1) Zhao, J.; Losego, M. D.; Lemaire, P. C.; Williams, P. S.; Gong, B.; Atanasov, S. E.; Blevins, T. M.; Oldham, C. J.; Walls, H. J.; Shepherd, S. D.; Browe, M. A.; Peterson, G. W.; Parsons, G. N. Highly Adsorptive, MOF-Functionalized Nonwoven Fiber Mats for Hazardous Gas Capture Enabled by Atomic Layer Deposition. Adv. Mater. Interfaces 2014, 1 (4), 1400040.

(2) Zhao, J.; Gong, B.; Nunn, W. T.; Lemaire, P. C.; Stevens, E. C.; Sidi, F. I.; Williams, P. S.; Oldham, C. J.; Walls, H. J.; Shepherd, S. D.; Browe, M. A.; Peterson, G. W.; Losego, M. D.; Parsons, G. N. Conformal and highly adsorptive metal–organic framework thin films via layer-by-layer growth on ALD-coated fiber mats. J. Mater. Chem. A 2015, 3 (4), 1458–1464.

(3) Zhao, J.; Nunn, W. T.; Lemaire, P. C.; Lin, Y.; Dickey, M. D.; Oldham, C. J.; Walls, H. J.; Peterson, G. W.; Losego, M. D.; Parsons, G. N. Facile Conversion of Hydroxy Double Salts to Metal-Organic Frameworks Using Metal Oxide Particles and Atomic Layer Deposition Thin-Film Templates. J. Am. Chem. Soc. 2015, 137 (43), 13756–13759.

(4) Zhao, J.; Lee, D. T.; Yaga, R. W.; Hall, M. G.; Barton, H. F.; Woodward, I. R.; Oldham, C. J.; Walls, H. J.; Peterson, G. W.; Parsons, G. N. Ultra-Fast Degradation of Chemical Warfare Agents Using MOF–Nanofiber Kebabs. Angew. Chem. Int. Ed. 2016, 55 (42), 13224–13228.

(5) Tovar, T. M.^#; Zhao, J.^#; Nunn, W. T.; Barton, H. F.; Peterson, G. W.; Parsons, G. N.; LeVan, M. D. Diffusion of CO₂ in Large Crystals of Cu-BTC MOF. J. Am. Chem. Soc. 2016, 138 (36), 11449–11452. (^#Equal Contribution)

(6) Zhao, J.; Wang, M.; Gleason, K. K. Stabilizing the Wettability of Initiated Chemical Vapor Deposited (iCVD) Polydivinylbenzene Thin Films by Thermal Annealing. Adv. Mater. Interfaces 2017, DOI: 10.1002/admi.201700270.