The study focuses on the evolution of financial institutions and capital markets as mechanisms for mobilizing private and public capital for large-scale sustainable development projects against the backdrop of a chronic funding gap for the SDGs and climate goals. The aim is to assess the dynamics of key segments of sustainable finance, identify barriers to scaling up, and determine factors that enhance the inflow of private investment into infrastructure, renewable energy, and climate adaptation. The methodology combines system and comparative legal analysis, descriptive statistics and time series analysis for 2012-2023, as well as correlation-regression modeling across emerging market economies and content analysis of regulatory documents and taxonomies. The empirical base includes reports from international organizations and market providers, academic publications, and aggregated statistics on green and sustainability-linked debt instruments, ensuring data triangulation and reliability of conclusions. The results record the exponential growth of the green bond market from USD 42,15 billion in 2015 to USD 575,24 billion in 2023, with a CAGR of 38,6%, while the share in total debt issuance reached only 0,67%. The issuance dynamics exhibit a nonlinear, near-logistic pattern, and achieving the USD 1 trillion annual issuance threshold within the next 2-3 years will require addressing standardization and verification barriers. The sectoral structure of financing is concentrated in renewable energy, green buildings, and clean transport (around 79%), whereas climate adaptation and biodiversity remain chronically underfunded and characterized by smaller average project sizes. A comparative assessment of ESG equity and bond index returns using the Sharpe ratio was applied to test the hypothesis regarding the risk-return profile of sustainable assets. Comparative analysis of returns and risks shows the competitiveness of ESG strategies: ESG indices demonstrate higher returns and better risk-adjusted performance than traditional benchmarks, including the green bond segment. Regression analysis reveals the key role of regulatory quality, financial market maturity, and the existence of a national green taxonomy as significant determinants of private capital inflows, while the effect of direct subsidies is statistically insignificant. The discussion indicates that scaling up will require standardization, verification, development of a project pipeline and blended finance mechanisms, as well as coordination among regulators and market participants to reduce risks and transaction costs. The conclusions highlight the financial viability of sustainable investments and the irreversible transformation of the financial architecture, while also emphasizing structural imbalances and the primacy of institutional frameworks over direct injections as a condition for mobilizing long-term capital.