Although weak, yet the H bond is more stronger than Van der waals forces and are specific in nature, which explains that it can be a chemisorption process. I need some more detailed answer.
The applied force in Hydrogen bond is an inter-molecular force, so it is physisorption.
Hydrogen bonds- intra and intermolecular come into existence when the electropositive H atom comes in the vicinity of an electronegative bond. They are weak intermolecular forces. Though they are stronger than vander Waals forces, the adsorption occurring trough them is by physisorption as no new compounds are formed at the surface of the adsorbent, which is a characteristic of chemisorption.
hydrogen bond strengths range from 4 kJ to 50 kJ per mole of hydrogen bonds. In molecules containing N-H, O-H or F-H bonds, the large difference in electronegativity between the H atom and the N, O or F atom leads to a highly polar covalent bond. Accordingly, there are many published articles considered H-bonding as type of the chemical adsorption such as Ziyong Chang, Liang Zeng, Chunbao Sun, Peng Zhao, Jiayu Wang, Lining Zhang , Yangge Zhu, Xiaoyue Qi. Adsorptive recovery of precious metals from aqueous solution using nanomaterials – A critical review, Coordination Chemistry Reviews, 445 (2021) 214072.
There is a great controversy on this point, as there are published articles have written that hydrogen bonding lies within chemical adsorption and others have made it within physical adsorption. Commonly, hydrogen bond strengths range from 4 kJ to 50 kJ per mole of hydrogen bonds and chemisorption process involves higher bonding energy, which is more than 40 kJ/mol. Accordingly, we consider H-bonding is a chemical interaction that falls within chemical adsorption.
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