The rapid growth in IoT applications has brought enormous challenges especially with achieving scalability and security in communicating devices. Traditional centralized security models are inadequate for managing the vast volume of data and diverse communication protocols in IoT environments, making them vulnerable to attacks such as Distributed Denial of Service (DDoS) and unauthorized access. Blockchain technology offers a decentralized alternative with its inherent properties of immutability, transparency, and decentralized consensus, providing a robust security solution for IoT communication. This paper presents a novel blockchain-based framework designed to secure IoT communication by addressing key challenges such as data integrity, privacy, and scalability. The proposed system integrates Ethereum’s blockchain, Zero Knowledge (ZK)-Rollups for Layer 2 scaling, and edge computing to optimise both performance and energy efficiency in large-scale IoT networks. The framework achieves a transaction throughput of 2,500 transactions per second with a median latency of 850 milliseconds. ZK-Rollups ensure that 99.8% of transactional data remains off-chain, improving privacy while reducing computational overhead. The system maintains 99.7% uptime during DDoS attacks and reduces energy consumption by 95% compared to traditional Proof of Work (PoW) blockchain systems. These findings indicate that the proposed blockchain-based framework is scalable, energy-efficient, and secure, making it a promising solution for large-scale IoT deployments in sectors such as smart cities, industrial automation, and healthcare.