Calcination synthesis of tin niobate loaded porous carbon nitride S-scheme heterojunction for photocatalytic H2 production and tetracycline degradation

•SnNb2O6/porous g-C3N4 heterojunction was constructed by calcination.•Photocatalytic H2 evolution increased by 12.28 times.•Larger surface area and improved charge separation are observed.•An S-scheme mechanism is proposed based on in-situ irradiation XPS.