Hammett Parameter in Microporous Solids as Macroligands for Heterogenized Photocatalysts

Summary

This materials chemistry study presents a rational design framework for heterogeneous photocatalysts by demonstrating that the Hammett parameter—a quantitative descriptor of ligand electronic effects from molecular chemistry—accurately predicts catalytic activity in both homogeneous and heterogenized systems. By anchoring organometallic complexes to microporous polymer and metal–organic framework supports as macroligands, the authors achieved competitive photocatalytic CO₂ reduction performance (28 h⁻¹ turnover frequency), suggesting that local electronic environment around the active site, rather than bulk porous support structure, governs efficiency.

Key measures

Hammett parameter values; catalytic turnover frequencies (h⁻¹); photocatalytic formate production rates

Outcomes reported

The study demonstrated that heterogeneous catalysts based on metal–organic frameworks and microporous polymers exhibit a linear correlation between ligand electronic effects (Hammett parameter) and catalytic activity, mirroring homogeneous catalyst behaviour. Rh-catalyzed photoreduction of CO2 was achieved with turnover frequencies up to 28 h⁻¹ using bipyridine-chelating macroligands, representing among the highest reported for heterogeneous photocatalytic formate production.

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