Conspectus
The Industrial Revolution has resulted in social and economic improvements,
but unfortunately, with the development of manufacturing and mining,
water sources have been pervaded with contaminants, putting Earth’s
freshwater supply in peril. Therefore, the segregation of pollutantssuch
as radionuclides, heavy metals, and oil spillsfrom water streams,
has become a pertinent problem. Attempts have been made to extract
these pollutants through chemical precipitation, sorbents, and membranes.
The limitations of the current remediation methods, including the
generation of a considerable volume of chemical sludge as well as
low uptake capacity and/or selectivity, actuate the need for materials
innovation. These insufficiencies have provoked our interest in the
exploration of porous organic polymers (POPs) for water treatment.
This category of porous material has been at the forefront of materials
research due to its modular nature, i.e., its tunable
functionality and tailorable porosity. Compared to other materials,
the practicality of POPs comes from their purely organic composition,
which lends to their stability and ease of synthesis. The potential
of using POPs as a design platform for solid extractors is closely
associated with the ease with which their pore space can be functionalized
with high densities of strong adsorption sites, resulting in a material
that retains its robustness while providing specified interactions
depending on the contaminant of choice.
POPs raise opportunities
to improve current or enable new technologies
to achieve safer water. In this Account, we describe some of our efforts
toward the exploitation of the unique properties of POPs for improving
water purification by answering key questions and proposing research
opportunities. The design strategies and principles involved for functionalizing
POPs include the following: increasing the density and flexibility
of the chelator to enhance their cooperation, introducing the secondary
sphere modifiers to reinforce the primary binding, and enforcing the
orientation of the ligands in the pore channel to increase the accessibility
and cooperation of the functionalities. For each strategy, we first
describe its chemical basis, followed by presenting examples that
convey the underlying concepts, giving rise to functional materials
that are beyond the traditional ones, as demonstrated by radionuclide
sequestration, heavy metal decontamination, and oil-spill cleanup.
Our endeavors to explore the applicability of POPs to deal with these
high-priority contaminants are expected to impact personal consumer
water purifiers, industrial wastewater management systems, and nuclear
waste management. In our view, more exciting will be new applications
and new examples of the functionalization strategies made by creatively
merging the strategies mentioned above, enabling increasingly selective
binding and efficiency and ultimately promoting POPs for practical
applications to enhance water security.