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oai:figshare.com:article/34023316 2026-09-29T11:04:31Z category_1 category_4 category_146 category_915 category_14 category_21 category_272 category_873 category_39 category_46 category_61 portal_63 item_type_6 month_year_09_2026

Synergistic Linkage Engineering in Donor–Acceptor Covalent Organic Frameworks for NIR-II Absorption and Efficient Photothermal Conversion Xi-Jun Wen (25136770) Peng-Ju Tian (25136773) Hui-Hui Sun (6717017) Zhi-Bei Zhou (11956338) Zhen-Xue Wang (25136776) Qiao-Yan Qi (4014329) Shun-Qi Xu (1432330) Shengqiang Xiao (1917091) Yubin Fu (1508008) Xin Zhao (71840) Biophysics Biochemistry Space Science Physical Sciences not elsewhere classified Molecular Biology Biotechnology Environmental Sciences not elsewhere classified Chemical Sciences not elsewhere classified Ecology Immunology Developmental Biology water evaporation rate tunable optoelectronic properties temperature increase 10 superior photothermal conversion significantly narrowed bandgap precisely defined structures synergistic linkage engineering da upon photoexcitation simultaneously achieve nir maximizing electronic delocalization ii light absorption ii photothermal applications da ), azo electronic delocalization ii absorption linkage replacement da achieves da ). work reveals voltage output sun irradiation state relaxation state dynamics photophysical behavior performance nir linked analogue intrinsically regulate integrated solar governing π fold higher critical role comprehensive spectroscopic 44 kg 262 mv 116 mv Covalent organic frameworks (COFs) are emerging crystalline porous polymers with precisely defined structures and tunable optoelectronic properties. However, developing COFs that simultaneously achieve NIR-II light absorption and controlled excited-state dynamics remains challenging, limiting their applications in advanced photothermal energy conversion. Herein, we report a strategy that synergistically integrates linkage engineering and donor–acceptor modulation to intrinsically regulate the photophysical behavior of COFs, as demonstrated by the synthesis of a novel donor–acceptor azo-linked COF (Azo-COF-DA). Compared with its imine-linked analogue (Im-COF-DA), Azo-COF-DA exhibits remarkable NIR-II absorption (1500 nm vs 650 nm) and a significantly narrowed bandgap (1.16 eV vs 2.34 eV), highlighting the critical role of azo linkages in maximizing electronic delocalization. Comprehensive spectroscopic and theoretical analyses reveal significantly enhanced vibronic coupling in Azo-COF-DA upon photoexcitation, thereby promoting efficient nonradiative relaxation. Consequently, Azo-COF-DA achieves a temperature increase 10.8-fold higher than that of Im-COF-DA, translating this superior photothermal conversion into a record COF-based thermoelectric output voltage of 262 mV under one-sun irradiation. Furthermore, an integrated solar-driven water evaporation–thermoelectric generator simultaneously achieves a water evaporation rate of 1.44 kg m^–2 h^–1 and a voltage output of 116 mV. This work reveals the importance of linkage replacement in governing π-electronic delocalization and excited-state relaxation, providing transferable structural design guidelines for tailoring excited-state dynamics in porous organic materials toward high-performance NIR-II photothermal applications. 2026-09-29T00:00:00Z Text Journal contribution 10.1021/jacs.6c07909.s001 https://figshare.com/articles/journal_contribution/Synergistic_Linkage_Engineering_in_Donor_Acceptor_Covalent_Organic_Frameworks_for_NIR-II_Absorption_and_Efficient_Photothermal_Conversion/34023316 CC BY-NC 4.0