Reversibly Modulating\nthe Selectivity of Carbon Dioxide\nReduction via Ligand-Driven Spin Crossover

Selectivity is an essential aspect in catalysis. At present,\nthe\nimprovement of the selectivity for complex reactions with multiple\npathways/products, for example the carbon dioxide reduction reaction\n(CO<sub>2</sub>RR), can usually be achieved for only one pathway/product.\nIt is still a challenge to reversibly modulate the selectivity between\ntwo reaction pathways or products of the CO<sub>2</sub>RR by one catalyst.\nHere, we propose the reversible modulation of selectivity between\ntwo products via spin crossover. By employing first-principles calculations,\nsix spin crossover molecular catalysts are found among 17 kinds of\ntransition metal embedded porphyrin derivatives (ppy_TM), where the\nchanges in axial ligand configurations can reversibly switch the spin\nstate of catalysts between high spin and low spin. For ppy_Os and\nppy_Ru, the alteration in spin state can effectively influence the\nreduction of CO<sub>2</sub> into either formic acid or carbon monoxide\nby changing the relative stability of the key intermediates *COOH\nand *HCOO.