(2021) Journal of Colloid and Interface Science_Hierarchical ZIF-decorated nanoflower-covered 3-dimensional foam for enhanced catalytic reduction of nitrogen-containing contaminants

Lin J.-Y., Lee J., Oh W.D., Kwon E., Tsai Y.-C., Lisak G., Phattarapattamawong S., Hu C., Lin K.-Y.A.

(Academic Press Inc.) Journal of Colloid and Interface Science ISSN: 219797 Vol.602 Issue. Article No. DOI: 10.1016/j.jcis.2021.05.098

Metal Organic Frameworks (MOFs) represent a promising class of metallic catalysts for reduction of nitrogen-containing contaminants (NCCs), such as 4-nitrophenol (4-NP). Nevertheless, most researches involving MOFs for 4-NP reduction employ noble metals in the form of fine powders, making these powdered noble metal-based MOFs impractical and inconvenient for realistic applications. Thus, it would be critical to develop non-noble-metal MOFs which can be incorporated into macroscale and porous supports for convenient applications. Herein, the present study proposes to develop a composite material which combines advantageous features of macroscale/porous supports, and nanoscale functionality of MOFs. In particular, copper foam (CF) is selected as a macroscale porous medium, which is covered by nanoflower-structured CoO to increase surfaces for growing a cobaltic MOF, ZIF-67. The resultant composite comprises of CF covered by CoO nanoflowers decorated with ZIF-67 to form a hierarchical 3D-structured catalyst, enabling this ZIF-67@Cu foam (ZIF@CF) a promising catalyst for reducing 4-NP, and other NCCs. Thus, ZIF@CF can readily reduce 4-NP to 4-AP with a significantly lower Ea of 20 kJ/mol than reported values. ZIF@CF could be reused over 10 cycles and remain highly effective for 4-NP reduction. ZIF@CF also efficiently reduces other NCCs, such as 2-nitrophenol, 3-nitrophenol, methylene blue, and methyl orange. ZIF@CF can be adopted as catalytic filters to enable filtration-type reduction of NCCs by passing NCC solutions through ZIF@CF to promptly and conveniently reduce NCCs. The versatile and advantageous catalytic activity of ZIF@CF validates that ZIF@CF is a promising and practical heterogeneous catalyst for reductive treatments of NCCs. © 2021 Elsevier Inc.

This work is supported by the Ministry of Science and Technology (MOST)(110-2636-E-005-003-), Taiwan, and financially supported by the “Innovation and Development Center of Sustainable Agriculture” from The Featured Areas Research Center Program within the framework of the Higher Education Sprout Project by the Ministry of Education (MOE), Taiwan. The authors gratefully acknowledge the use of SQUID000200 of MOST110-2731-M-006-001 belonging to the Core Facility Center of National Cheng Kung University.