Chemistry that works: designed enzymes, honest failure modes, and waste made useful
Five preprints this week share one concern: chemistry that holds up outside the flask — designed photoenzymes, a directing-group-free amination, a diagnosed photocatalyst failure, gold recovered from e-waste, and PFAS recycled into a fluoride source.
- Wang and colleagues used substrate-recognition-guided computational design to build de novo photoenzymes carrying abiotic thioxanthone photosensitizers; for 4-alkenylcyclohexanol deracemization they report catalytic efficiency above 1.5x10^5 M^-1 s^-1 and enantiomeric excess up to 99%, in a preprint on ChemRxiv. Self-reported m:…1492
- Uherek and colleagues aminated alkanes without directing groups using PTAD as a sigma-acid with a gold(I) catalyst in HFIP; the reaction is site-selective and stereoretentive, with selectivity following carbocation stability through a hydride-transfer mechanism, in a preprint on ChemRxiv. Self-reported m:…8765
- Abudukade and colleagues identified photoinduced Sr leaching as the primary deactivation pathway for SrTiO3 photocatalysts during overall water splitting; activity decays within tens of minutes under 365 nm light at 20 mW/cm2 while Pt-covered regions stay compositionally stable, in a preprint on ChemRxiv. Self-reported m:…0115
- Li and colleagues made mechanically robust porous organic polymer monoliths with surface areas up to 1055 m2/g; they adsorb 3225 mg/g AuCl4- and 1375 mg/g PdCl4 2-, recover 99% of gold from e-waste leachates at 1 L/h in continuous flow, and run Suzuki coupling at 2.75 kg_biphenyl/L_POP per day, in a preprint on ChemRxiv. Self-reported m:…5081
- Hattori and colleagues recycled PFAS mechanochemically: ball milling PTFE with magnesium gives MgF2, a second milling step with NaOH gives water-soluble NaF, and the recovered NaF serves as fluoride source for one-pot fluorination of sulfonyl and acyl chlorides, in a preprint on ChemRxiv. Self-reported m:…1203
Catalysts built on purpose
In a preprint on ChemRxiv, Wang and colleagues describe a design strategy for photoenzymes that builds enantioselectivity in through substrate recognition, rather than fishing for it with directed evolution. Their approach uses computational design to construct a catalytic environment around the target substrate, then gives the designed protein excited-state reactivity by incorporating an abiotic thioxanthone photosensitizer. On the deracemization of 4-alkenylcyclohexanols, the designed photoenzymes reach catalytic efficiencies above 1.5x10^5 M^-1 s^-1 and enantiomeric excesses up to 99%, with crystal structure and kinetic analysis supporting substrate-recognition-dependent energy transfer in the active site. m:…1492
A second preprint, from Uherek and colleagues, removes a different crutch: directing groups in alkane C-H amination. Using phenyl triazolinedione (PTAD) as a sigma-acid with a gold(I) catalyst in hexafluoroisopropanol (HFIP), the method aminates alkanes site-selectively and retains stereochemistry. It discriminates between similar C-H bonds — tertiary versus secondary, equatorial versus axial, cyclic versus linear — with selectivity that follows carbocation stability, consistent with a carbocationic mechanism involving hydride transfer. m:…8765
The common move is selectivity engineered in rather than coaxed out: one team designs the protein around the substrate, the other lets the substrate's own carbocation stability dictate where the reaction lands. Both reports arrive as preprints on ChemRxiv, so the results rest on the authors' own experiments. m:…1492 m:…8765
A failure, precisely diagnosed
Abudukade and colleagues add a different kind of useful result: a failure mode, named. In their preprint, photoinduced strontium leaching is identified as the primary deactivation pathway for SrTiO3 photocatalysts during overall water splitting. Under UV irradiation the exposed surfaces transform into a Ti-rich, TiO2-like phase with high defect density and unfavorable band alignment, which drives charge-carrier recombination and activity decay. Activity falls off within tens of minutes under 365 nm light at 20 mW/cm2, while platinum-covered regions of the surface stay compositionally stable. m:…0115
Waste streams as feedstocks
Li and colleagues report a scalable synthesis of porous organic polymer gels that mold into mechanically robust monoliths with surface areas up to 1055 m2/g. The imine- and aminal-linked materials adsorb up to 3225 mg/g of AuCl4- and 1375 mg/g of PdCl4 2-, and in continuous-flow columns they recover 99% of gold from electronic-waste leachates at a throughput of 1 L/h. Once loaded with noble metal, the same columns double as continuous-flow Suzuki reactors with a space-time yield of 2.75 kg_biphenyl/L_POP per day. m:…5081
Hattori and colleagues close a loop on the fluorine side. Ball milling PTFE with magnesium converts the fluoropolymer into magnesium fluoride, and a second milling step with sodium hydroxide turns that into water-soluble sodium fluoride. The recovered NaF then serves as the fluoride source for one-pot fluorination of sulfonyl and acyl chlorides — waste PFAS in, usable reagent out. m:…1203
The thread
Across five preprints, the through-line is chemistry built to survive contact with reality: catalysts designed for selectivity, a benchmark photocatalyst whose failure is finally specified, and processes that treat waste streams as feedstocks. Each report is a preprint on ChemRxiv, so independent replication is still pending. m:…1492 m:…8765 m:…0115 m:…5081 m:…1203
For a practitioner, the practical question these reports answer is where to invest effort: design the selectivity in up front, diagnose deactivation before scaling, and route waste streams back into the process. That is the week's message, stated plainly. m:…1492 m:…0115 m:…5081 m:…1203
What is still unresolved
- The photoenzyme paper discloses no open-source code or software platform for its computational design, and independent replication is not shown.
- The C-H amination paper states no explicit substrate-scope limits or yield benchmarks for complex intermediates.
- The SrTiO3 study proposes no stabilization strategy against Sr leaching, and lifetimes under real sunlight are not tested.
- The POP study does not detail long-term column fouling or regeneration cycles in continuous operation.
- The PFAS recycling paper provides no scale-up data beyond the reported mechanochemical steps.
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