Sulfur-Rich Thioorthoester Polymers as Powerful Metal Scavengers

Sulfur-containing materials have played a central role for decades in the coordination chemistry of precious metals as well as in environmental and process purification.

The technology presented here makes use, for the first time, of a dynamic covalent thioorthoester chemistry to produce networked, insoluble polymers with an exceptionally high sulfur content of approximately 44–66 wt%. The combination of strong chemical binding, porous morphology, and mechanical stability represents a qualitative technological leap compared with existing solutions.

1. Palladium Scavenging in the Pharmaceutical and Fine Chemical Industry (Lead Application)

This technology addresses one of the most economically critical use cases in the chemical and pharmaceutical industries: the late-stage removal of palladium residues from catalytic synthesis processes.

Palladium is indispensable for modern C–C and C–H coupling reactions, yet it is subject to strict regulatory limits in pharmaceutical active ingredients and their intermediates.

The innovative thioorthoester polymers enable:

• highly efficient polishing of process and product streams
• application under industrially relevant conditions (organic solvents, moderate temperatures)
• recovery of high-value precious metals

2. Antimony Removal from Water and Process Streams

Antimony is a toxic, potentially carcinogenic metalloid with increasing regulatory relevance in industrial wastewater and environmental media. Commercial metal scavengers/adsorbents are only available to a limited extent and often show insufficient reusability.

The innovative thioorthoester polymers enable:

• selective Sb adsorption at low concentrations
• multiple regeneration cycles with limited capacity loss
• use in industrial water treatment and specialty chemical applications

3. Recovery of Additional Precious and Industrially Relevant Metals

Due to the very high sulfur density and porous structure of the thioorthoester polymers, selective binding of further thiophilic metals such as gold, silver, and platinum is possible.

This opens up applications in:

• Recycling and urban mining processes,
• High-purity chemicals,
• Selective separation steps in complex matrices.

Existing metal scavengers/adsorbents frequently face a trade-off between capacity, selectivity, and stability.

1.Economically critical metal contaminants

• Palladium residues cause high cleaning and validation costs.
• Inadequate removal can lead to batch losses or regulatory risks.

2. Environmental and ESG-driven requirements

• Antimony and comparable semi-metals are the focus of stricter limits.
• Operators need robust, reusable, and selective materials.

3. Disadvantages of existing metal scavengers/adsorbents

• Conflicting goals between capacity, selectivity, and stability.
• High operating costs due to disposable materials.
• Limited scalability and differentiation

The innovative technology is based on a novel class of network-like thioorthoester polymers, which are produced via iron-catalyzed polycondensation from commercially available precursors. Economic Impact includes reduced sorbent consumption, lower disposal costs, opportunity for precious metal recovery, and improved total cost of ownership (TCO).

Key design features:

• Very high sulfur content - high affinity to precious metals and metals relevant to industrial processes
• Network structure - complete insolubility in water and organic solvents
• Porous microstructure - high accessibility of active binding sites
• Dynamic covalent C–S bonds as a structure-forming element
• Rare example of unique structure - patentable scavenger material

The material properties can be chemically adjusted in a modular fashion (e.g., type of dithiol building blocks), which allows further adaptation to different industrial requirements.

Palladium:

• Experimentally demonstrated adsorption capacities of 41 mg Pd per g of polymer under process-relevant conditions in organic solvents.
• The above value corresponds to approximately twice the capacity of the market-leading material QuadraPureTU® (22 mg Pd per g of polymer) in a direct comparison under identical conditions.
• High selectivity toward palladium in the presence of competing metals.

Antimony:

• Effective adsorption of 2.2 mg Sb per g of polymer, even at low concentrations.
• Regeneration by repeated washing with hydrochloric acid (residual Sb content below 5% of the initial value) and reuse with only a moderate capacity loss (approx. 20%).
• Advantageous compared to many existing materials that must be used as single-use products.

Economic Impact:

• Reduced sorbent consumption,
• Lower disposal costs,
• Possibility of precious metal recovery,
• Improved total cost of ownership (TCO).

Process Integration and Scalability:

• Production at moderate temperatures using established catalysts.
• Industrially compatible solid–liquid separation (filtration, packed-bed systems).
• Suitable for various form factors such as powders/granulates, cartridges, monoliths, or composite materials.
• Largely drop-in compatible with existing process lines.

For industrial partners, the technology offers:

• Clear differentiation from existing metal scavengers/adsorbents,
• Scientifically validated performance,
• Patent protection,
• Flexible licensing models (exclusive/application-specific),
• Opportunity for cooperation.

https://onlinelibrary.wiley.com/doi/10.1002/anov.70000

Angewandte Chemie Novit - 2025 - Kraus - Thioorthoester Polymers as Sulfur-Rich Materials in Metal Scavengers and Battery published