In Situ Synthesis of HKUST‐1@Biochar Composite for CO ₂ Adsorption

ABSTRACT The rapid escalation of anthropogenic CO 2 emissions sustainable and cost‐effective carbon capture solutions. For CO 2 adsorption, a variety of CO 2 sorptive materials were explored. Among them, biochar is one of the materials that is economically viable, and on the other hand, MOF is one of the highly porous materials. This study utilizes an in‐situ approach to synthesize a novel hybrid material, CLPB@HKUST‐1 ( Citrus limetta peel biochar@HKUST‐1), without prior chemical activation of the CLPB, to understand its impact on CO 2 capture capacity. The materials were synthesized and characterized using powder x‐ray diffraction (PXRD), FTIR, SEM, BET surface analysis, and TGA, followed by high‐pressure CO 2 and N 2 adsorption isotherms at 25°C. Pristine CLPB exhibited negligible porosity (surface area 0.12 m 2 ·g −1 ) with low CO 2 uptake (1.54 mmol·g −1 at 10 bar), whereas HKUST‐1 showed higher surface area (539.01 m 2 ·g −1 ) and CO 2 capacity (4.83 mmol·g − 1 ). The HKUST‐1@CLPB hybrid material displayed a significant enhancement over CLPB, with surface area increased to 132.5 m 2 ·g −1 , micropore volume to 0.048 cm 3 ·g −1 , and CO 2 uptake to 2.03 mmol·g −1 at 10 bars, corresponding to a 31.3% improvement. The adsorption selectivity of the samples for CO 2 /N 2 binary mixture, at 10 bar, varies as HKUST‐1@CLPB > CLPB > HKUST‐1. Structural and spectroscopic analyses confirmed the successful integration of HKUST‐1 and the biochar matrix, with interfacial interactions modifying adsorption environments. This study provides critical insights into structure‐property‐performance relationships in MOF‐biochar hybrid material and finds its novelty in the upgrading of the waste‐derived biochar into a functional sorbent by combining structural porosity with surface functionalities.