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• Bimetallic nitride heterostructures is constructed to broaden the optical response. • The C@VN/TiN sample are synthesized by ammonia-assisted one-step calcination. • The C@VN/TiN sample has the best photoreduction CO 2 performance. There are still many challenges in inhibiting the recombination and differentiation of photogenerated carriers from promoting the conversion of CO 2 into hydrocarbons. Based on the functional differentiation of different metal sites, bimetallic nitride heterostructures is constructed to broaden the optical response and promote the separation of charge carriers in this work. Herein, carbon substrate-loaded double nitride heterostructure composites C@VN/TiN are synthesized by ammonia-assisted one-step calcination. In all samples, the C@VN/TiN-3 sample has the best photoreduction CO 2 performance with the promotion of lactic acid (LA) reagent. And the CH 4 yield of the C@VN/TiN-3 sample is 775 μmol g−1 h-1, which is 7.6 times and 10.3 times higher than C@VN (102 μmol g−1 h-1) and C@TiN (75 μmolg−1 h-1), respectively. The generation, separation, and migration of photogenerated electron-hole pairs are studied kinetically through transient photocurrent responses, electrochemical impedance spectroscopy and photoluminescence spectroscopy. The position and process of adsorption and activation of CO 2 and H 2 O are deduced by in situ characterization and reaction potential, and the determined possible path is explored by the peak of intermediates. This paper reveals the important roles of co-catalytic agents, ohmic junctions, and the function of bimetallic actives in enhancing photocatalytic activity, providing new ideas for constructing efficient photocatalysts. [ABSTRACT FROM AUTHOR]

• Bio-inspired hybrid materials as photocatalysts. • Biopolymers as templates, supports, immobilisation substrates for photocatalysts. • Enzymes, peptides, proteins based materials-coupling biodegradation. • Greener synthesis of metal based photocatalysts-opportunities and developments. • Photocatalytic degradation of various pollutants by biomaterials-based catalysts. New materials tend to revolutionize scientific community and human race on a larger level. Scientists worldwide have not just been working on some wondrous materials with superior properties but have progressively focused on greener bio-inspired or bio-compatible materials for sustainable development. An increasing number of researchers have been working on using biomaterials as a part of photocatalysts for stability, bio-compatibility, generation of more reactive oxygen species and enhancement of optical absorption. In this review we have focussed on photocatalysts based on biopolymers, biochar, carbons, enzymes and proteins. This review presents various types of bio-inspired nanomaterials and their use as sustainable photocatalysts for degrading various venomous pollutants. The effect of pyrolysis temperature, temperature gradient, feedstock and synthetic route of biochar and carbon on the properties and final performance of derived photocatalysts has also been discussed. The increase in surface area, active adsorption sites, electron shuttling & reservoir properties, high visible absorption, charge separation and biocompatibility have also been elaborated. As far as photocatalytic performance is considered such bio-based photocatalysts are often questioned for their stability under such conditions and poor activity as compared to pure metal-based catalysts. These limitations can be overcome by choice of materials, modifications, new designing routes and coupling of biological methods and photocatalysis for removal of pollutants even from water from waste water treatment plants. Suitable modification to biomolecules as functionalisation has been reported for better adsorption of pollutants. The role of biomaterials in generation of reactive oxygen species, recombination suppression, interactions with pollutants, optical absorption, separation of charge carriers, shuttling and electron flow has also been elaborately explained. The concerns, challenges and future opportunities are also included in this review. [ABSTRACT FROM AUTHOR]