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oai:figshare.com:article/34020458 2026-09-29T02:05:17Z category_1 category_4 category_915 category_7 category_21 category_873 category_46 category_64 category_69 category_132 category_134 portal_63 item_type_6 month_year_09_2026

From Surface Buffering to Bulk Ion Exchange: Mapping the Acid Response of Potassium Poly(Heptazine Imide) (K-PHI) Julia Sinisi (14119430) Gabriel A. A. Diab (22754087) Titus Ekabat (25133750) Sebastian Bette (1813798) Viola Duppel (1680721) Ivo F. Teixeira (1408582) Stefan Repp (9411789) Bettina V. Lotsch (1467520) Biophysics Biochemistry Physical Sciences not elsewhere classified Medicine Biotechnology Chemical Sciences not elsewhere classified Immunology Cancer Inorganic Chemistry Infectious Diseases Virology sup >+</ sup stable zeta potential suggesting proton excess proton adsorption balanced acid stability regime yet lower ph bulk ion exchange proton adsorption cation exchange acid response ph 4 ph 3 ph 2 systematic study solution properties simultaneous consideration protonated poly promising material potassium poly optoelectronic changes heptazine imide energy storage causes structural buffering coincides buffer limit aqueous media Potassium poly(heptazine imide) (K-PHI) is a promising material for photocatalysis and energy storage, yet its application in aqueous media is limited by protonation. Cation exchange to protonated poly(heptazine imide) (H-PHI) causes structural and optoelectronic changes. Herein, a systematic study of its acid stability regime and protonation threshold is presented through simultaneous consideration of PHI’s bulk, interface, and solution properties. Down to pH 3.0, solutions are buffered by proton adsorption while the particle bulk retains structural integrity, pointing to coexistence of H⁺ at the surface and K⁺ in the bulk. Within this regime down to pH 4.0, buffering coincides with a stable zeta potential, consistent with proton adsorption balanced by counterions. At yet lower pH, the buffer limit (pH 3.0) is characterized by surface destabilization, suggesting proton excess. At pH 2.0, protonation proceeds via bulk ion exchange and H-PHI formation. 2026-09-28T00:00:00Z Text Journal contribution 10.1021/acs.langmuir.6c03166.s001 https://figshare.com/articles/journal_contribution/From_Surface_Buffering_to_Bulk_Ion_Exchange_Mapping_the_Acid_Response_of_Potassium_Poly_Heptazine_Imide_K-PHI_/34020458 CC BY-NC 4.0