Ab Initio Free Energy Simulations with Chemical Accuracy: Adsorption and Catalysis in Nanoporous Materials

The design of improved nanoporous materials, such as MOFs for water harvesting and carbon capture and zeolites for hydrocarbon synthesis and conversion, requires the reliable prediction of rate and equilibrium constants, i.e. free energies, for adsorption/desorption and elementary reaction steps with no other input than the atomic positions. To be relevant, predictions have to be made with an accuracy that is comparable to experiment. 

For realistic models with hundreds of atoms in the simulation cell, this is a challenging problem of computational quantum chemistry. We present an ab initio divide-and-conquer approach that (i) combines a high-level QM description of the reaction/adsorption site with a low level description of the full periodic solid QM (QM – quantum mechanics) to calculate energies, (ii) samples the potential energy surface locally with anharmonic partition functions, and (iii) uses Grand Canonical Monte Carlo lattice simulations for global sampling over different sites. 

We show that chemical accuracy (±4 kJ/mol) is reached for adsorption and separation of small molecules (H₂O, CO₂, CH₄, N₂, CO) in MOFs and for adsorption and conversion of alkanes and alkenes in acidic zeolites.

Speaker Biography

Joachim Sauer received the Dr. rer. nat. degree in Chemistry from Humboldt University in Berlin in 1974, and the Dr. sc. nat. degree from the Academy of Sciences in (East-)Berlin in 1985. He is Senior Researcher at Humboldt University in Berlin where he was Professor of Theoretical Chemistry from 1993 – 2017. Since 2006 he is external member of the Fritz Haber Institute, Berlin (Max Planck Society). He is member of several Academies including the German National Academy Leopoldina, the Royal Society (London) and the American Academy of Arts and Sciences

His research has explored the application of quantum chemical methods in surface chemistry, particularly adsorption and catalysis. He has published more than 400 papers, notably in the area of the structure and reactivity of transition metal oxide catalysts, zeolites and metal-organic frameworks, and he has given more than 500 invited lectures. The Society of German Chemists (GDCh) awarded him with the Liebig Medal, the Federation of European Catalysis Societies (EFCATS) with the Francis Gault Lectureship, the American Chemical Society with the ACS Award in Surface Chemistry, and the World Association of Theoretical and Computational Chemists (WATOC) with the Schrödinger medal.