Solar-driven, sustainable, and complete removal of sulfamethoxazole (SMX), a refractory emerging contaminant

in aquatic systems, is paramount. Although graphitic carbon nitride (g-C3N4) is a potential metal-free photocatalyst,

it remains inefficient in removing SMX. However, its efficiency can be improved by increasing its

specific surface area and enhancing carrier transport through morphological modifications and elemental

doping. Herein, we synthesized B-doped porous tubular g-C3N4 (TGCN-Bx) using a supramolecular self-assembly

approach. The introduction of B in the g-C3N4 matrix reduced the band gap, which enhanced its visible light

absorption and photo-reduction ability. The one-dimensional thin-walled tubular structure with a high aspect

ratio exhibited oriented transport and separation of photo-generated carriers. A tubular wall containing

numerous pores could expose a large number of reactive sites. Moreover, multiple reflations of incident light

inside the tubular led to improved light-harvesting ability. These factors contributed to the improved photocatalytic

activity of TGCN-B2 for the decomposition of SMX aided by visible light. TGCN-B2 showed 5.2 times

better photodegradation activity than pure g-C3N4, achieving the remarkable result of > 99 % degradation of

SMX after 30 min of visible-light exposure at pH 7. The radical scavenger experiment and electron spin resonance

(ESR) spectra show that hydroxyl radicals (•OH), superoxide radicals (O2●???? ), holes (h+), and contributed to the

photodecomposition of SMX over TGCN-B2. This study provides perspective into the simultaneous doping of

foreign atoms and architectural control of g-C3N4 for the remediation of water contaminated with antibiotics.