Molecular imprinting forms a polymer around a template molecule so that, after the template is removed, the material retains recognition cavities that match the target's shape and chemical functions. When these molecularly imprinted polymers are integrated with biochar, the resulting composites combine broad adsorption capacity with selective binding sites for chosen contaminants in water and other complex matrices.
"Our goal is to turn low-value biomass into high-value smart sorbents that can precisely target contaminants rather than treating all pollutants as the same," says lead author Jiaheng Li of Capital Normal University.
The review, published in Biochar X, systematically summarizes how researchers prepare, modify, and apply molecularly imprinted biochar materials and what makes them different from conventional adsorbents. The authors describe three key design choices: the imprinting mechanism, the polymerization method, and the selection of building blocks such as functional monomers, crosslinkers, and initiators.
Noncovalent imprinting, which relies on hydrogen bonding and other weak interactions, has become the most widely used route because it is simple, fast, and compatible with water treatment conditions. Common polymerization strategies on biochar supports include precipitation polymerization, emulsion polymerization, electropolymerization on electrodes, and sol - gel processes, each offering different control over particle size, film thickness, and pore structure.
"By tuning the chemistry on the biochar surface, we can design materials that not only capture a pollutant quickly but also recognize it among dozens of similar chemicals," notes corresponding author Yuhu Zhang.
Many of the most urgent targets for these materials are trace organic pollutants that are highly toxic at low concentrations, such as antibiotics, pesticides, plasticizers, and disinfection by-products. Standard treatment plants struggle with these compounds because they often occur in complex mixtures and at levels that are difficult to remove efficiently.
Molecularly imprinted magnetic biochar has been used to selectively remove antibiotics such as oxytetracycline and sulfamethoxazole from water, combining fast adsorption with easy magnetic recovery and reuse. Other systems imprint biochar composites to recognize herbicides, pharmaceutical residues, or polycyclic aromatic hydrocarbons, then pair adsorption with advanced oxidation or photocatalysis to degrade the captured pollutants rather than simply transferring them to another waste stream.
In one example highlighted in the review, an imprinted biochar achieved more than 80 percent equilibrium adsorption of the carcinogenic compound naphthalene within minutes, while a coupled oxidation process degraded the molecule and reopened the imprinted cavities for repeated use.
The same recognition principle that supports environmental cleanup can also be used to build highly selective sensors and analytical tools. By growing imprinted films directly on conductive biochar-based electrodes, researchers have created electrochemical sensors for antibiotics, heavy metal ions, and plasticizers that respond quickly and selectively in complex samples.
Molecularly imprinted biochar can serve as a solid-phase extraction material to preconcentrate trace contaminants from biological, food, or environmental samples before chromatographic analysis, improving detection limits and reducing matrix interference. Electropolymerized imprinted layers on biochar substrates allow precise control over film thickness and are compatible with in situ monitoring in real time. According to the review, this combination of low-cost biomass-derived carbon and tailor-made recognition sites is especially promising for portable sensors and on-site monitoring of water quality. Such systems could offer selective detection and treatment in settings where centralized infrastructure is limited.
The authors emphasize that environmental safety and scalability must be addressed before molecularly imprinted biochar can be widely deployed. Potential risks include the release of residual monomers, crosslinkers, or metal oxide nanoparticles from the composite, as well as toxicity associated with the biochar itself if production conditions are not well controlled.
The review calls for greener synthesis routes, including water-based polymerization, less toxic functional monomers, and careful control of pyrolysis conditions to limit hazardous by-products. It also highlights the need for long-term aging studies and full life cycle assessment to quantify impacts such as carbon footprint, leaching behavior, and ecotoxicity compared with existing technologies.
"From the lab perspective, these materials already show clear advantages in selectivity, capacity, and reusability," says Zhang. "The next step is to prove that they are safe, economical, and robust enough for continuous operation in real treatment systems."
By integrating molecular recognition with biomass recycling, molecularly imprinted biochar materials offer a path toward smarter, more selective pollution control in a warming and increasingly resource-constrained world.
Research Report: Advances in the preparation, application, and synergistic studies of biochar materials by molecular imprinting techniques: a review
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